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diff --git a/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt b/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt new file mode 100644 index 0000000000..bba5ecdd64 --- /dev/null +++ b/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt @@ -0,0 +1,3666 @@ +
+ ------------------------------------------------------------
+ This is the second part of a two part file.
+ This is a list of changes to pccts 1.33 prior to MR13
+ For more recent information see CHANGES_FROM_133.txt
+ ------------------------------------------------------------
+
+ DISCLAIMER
+
+ The software and these notes are provided "as is". They may include
+ typographical or technical errors and their authors disclaims all
+ liability of any kind or nature for damages due to error, fault,
+ defect, or deficiency regardless of cause. All warranties of any
+ kind, either express or implied, including, but not limited to, the
+ implied warranties of merchantability and fitness for a particular
+ purpose are disclaimed.
+
+
+#153. (Changed in MR12b) Bug in computation of -mrhoist suppression set
+
+ Consider the following grammar with k=1 and "-mrhoist on":
+
+ r1 : (A)? => ((p>>? x /* l1 */
+ | r2 /* l2 */
+ ;
+ r2 : A /* l4 */
+ | (B)? => <<q>>? y /* l5 */
+ ;
+
+ In earlier versions the mrhoist routine would see that both l1 and
+ l2 contained predicates and would assume that this prevented either
+ from acting to suppress the other predicate. In the example above
+ it didn't realize the A at line l4 is capable of suppressing the
+ predicate at l1 even though alt l2 contains (indirectly) a predicate.
+
+ This is fixed in MR12b.
+
+ Reported by Reinier van den Born (reinier@vnet.ibm.com)
+
+#153. (Changed in MR12a) Bug in computation of -mrhoist suppression set
+
+ An oversight similar to that described in Item #152 appeared in
+ the computation of the set that "covered" a predicate. If a
+ predicate expression included a term such as p=AND(q,r) the context
+ of p was taken to be context(q) & context(r), when it should have
+ been context(q) | context(r). This is fixed in MR12a.
+
+#152. (Changed in MR12) Bug in generation of predicate expressions
+
+ The primary purpose for MR12 is to make quite clear that MR11 is
+ obsolete and to fix the bug related to predicate expressions.
+
+ In MR10 code was added to optimize the code generated for
+ predicate expression tests. Unfortunately, there was a
+ significant oversight in the code which resulted in a bug in
+ the generation of code for predicate expression tests which
+ contained predicates combined using AND:
+
+ r0 : (r1)* "@" ;
+ r1 : (AAA)? => <<p LATEXT(1)>>? r2 ;
+ r2 : (BBB)? => <<q LATEXT(1)>>? Q
+ | (BBB)? => <<r LATEXT(1)>>? Q
+ ;
+
+ In MR11 (and MR10 when using "-mrhoist on") the code generated
+ for r0 to predict r1 would be equivalent to:
+
+ if ( LA(1)==Q &&
+ (LA(1)==AAA && LA(1)==BBB) &&
+ ( p && ( q || r )) ) {
+
+ This is incorrect because it expresses the idea that LA(1)
+ *must* be AAA in order to attempt r1, and *must* be BBB to
+ attempt r2. The result was that r1 became unreachable since
+ both condition can not be simultaneously true.
+
+ The general philosophy of code generation for predicates
+ can be summarized as follows:
+
+ a. If the context is true don't enter an alt
+ for which the corresponding predicate is false.
+
+ If the context is false then it is okay to enter
+ the alt without evaluating the predicate at all.
+
+ b. A predicate created by ORing of predicates has
+ context which is the OR of their individual contexts.
+
+ c. A predicate created by ANDing of predicates has
+ (surprise) context which is the OR of their individual
+ contexts.
+
+ d. Apply these rules recursively.
+
+ e. Remember rule (a)
+
+ The correct code should express the idea that *if* LA(1) is
+ AAA then p must be true to attempt r1, but if LA(1) is *not*
+ AAA then it is okay to attempt r1, provided that *if* LA(1) is
+ BBB then one of q or r must be true.
+
+ if ( LA(1)==Q &&
+ ( !(LA(1)==AAA || LA(1)==BBB) ||
+ ( ! LA(1) == AAA || p) &&
+ ( ! LA(1) == BBB || q || r ) ) ) {
+
+ I believe this is fixed in MR12.
+
+ Reported by Reinier van den Born (reinier@vnet.ibm.com)
+
+#151a. (Changed in MR12) ANTLRParser::getLexer()
+
+ As a result of several requests, I have added public methods to
+ get a pointer to the lexer belonging to a parser.
+
+ ANTLRTokenStream *ANTLRParser::getLexer() const
+
+ Returns a pointer to the lexer being used by the
+ parser. ANTLRTokenStream is the base class of
+ DLGLexer
+
+ ANTLRTokenStream *ANTLRTokenBuffer::getLexer() const
+
+ Returns a pointer to the lexer being used by the
+ ANTLRTokenBuffer. ANTLRTokenStream is the base
+ class of DLGLexer
+
+ You must manually cast the ANTLRTokenStream to your program's
+ lexer class. Because the name of the lexer's class is not fixed.
+ Thus it is impossible to incorporate it into the DLGLexerBase
+ class.
+
+#151b.(Changed in MR12) ParserBlackBox member getLexer()
+
+ The template class ParserBlackBox now has a member getLexer()
+ which returns a pointer to the lexer.
+
+#150. (Changed in MR12) syntaxErrCount and lexErrCount now public
+
+ See Item #127 for more information.
+
+#149. (Changed in MR12) antlr option -info o (letter o for orphan)
+
+ If there is more than one rule which is not referenced by any
+ other rule then all such rules are listed. This is useful for
+ alerting one to rules which are not used, but which can still
+ contribute to ambiguity. For example:
+
+ start : a Z ;
+ unused: a A ;
+ a : (A)+ ;
+
+ will cause an ambiguity report for rule "a" which will be
+ difficult to understand if the user forgets about rule "unused"
+ simply because it is not used in the grammar.
+
+#148. (Changed in MR11) #token names appearing in zztokens,token_tbl
+
+ In a #token statement like the following:
+
+ #token Plus "\+"
+
+ the string "Plus" appears in the zztokens array (C mode) and
+ token_tbl (C++ mode). This string is used in most error
+ messages. In MR11 one has the option of using some other string,
+ (e.g. "+") in those tables.
+
+ In MR11 one can write:
+
+ #token Plus ("+") "\+"
+ #token RP ("(") "\("
+ #token COM ("comment begin") "/\*"
+
+ A #token statement is allowed to appear in more than one #lexclass
+ with different regular expressions. However, the token name appears
+ only once in the zztokens/token_tbl array. This means that only
+ one substitute can be specified for a given #token name. The second
+ attempt to define a substitute name (different from the first) will
+ result in an error message.
+
+#147. (Changed in MR11) Bug in follow set computation
+
+ There is a bug in 1.33 vanilla and all maintenance releases
+ prior to MR11 in the computation of the follow set. The bug is
+ different than that described in Item #82 and probably more
+ common. It was discovered in the ansi.g grammar while testing
+ the "ambiguity aid" (Item #119). The search for a bug started
+ when the ambiguity aid was unable to discover the actual source
+ of an ambiguity reported by antlr.
+
+ The problem appears when an optimization of the follow set
+ computation is used inappropriately. The result is that the
+ follow set used is the "worst case". In other words, the error
+ can lead to false reports of ambiguity. The good news is that
+ if you have a grammar in which you have addressed all reported
+ ambiguities you are ok. The bad news is that you may have spent
+ time fixing ambiguities that were not real, or used k=2 when
+ ck=2 might have been sufficient, and so on.
+
+ The following grammar demonstrates the problem:
+
+ ------------------------------------------------------------
+ expr : ID ;
+
+ start : stmt SEMI ;
+
+ stmt : CASE expr COLON
+ | expr SEMI
+ | plain_stmt
+ ;
+
+ plain_stmt : ID COLON ;
+ ------------------------------------------------------------
+
+ When compiled with k=1 and ck=2 it will report:
+
+ warning: alts 2 and 3 of the rule itself ambiguous upon
+ { IDENTIFIER }, { COLON }
+
+ When antlr analyzes "stmt" it computes the first[1] set of all
+ alternatives. It finds an ambiguity between alts 2 and 3 for ID.
+ It then computes the first[2] set for alternatives 2 and 3 to resolve
+ the ambiguity. In computing the first[2] set of "expr" (which is
+ only one token long) it needs to determine what could follow "expr".
+ Under a certain combination of circumstances antlr forgets that it
+ is trying to analyze "stmt" which can only be followed by SEMI and
+ adds to the first[2] set of "expr" the "global" follow set (including
+ "COLON") which could follow "expr" (under other conditions) in the
+ phrase "CASE expr COLON".
+
+#146. (Changed in MR11) Option -treport for locating "difficult" alts
+
+ It can be difficult to determine which alternatives are causing
+ pccts to work hard to resolve an ambiguity. In some cases the
+ ambiguity is successfully resolved after much CPU time so there
+ is no message at all.
+
+ A rough measure of the amount of work being peformed which is
+ independent of the CPU speed and system load is the number of
+ tnodes created. Using "-info t" gives information about the
+ total number of tnodes created and the peak number of tnodes.
+
+ Tree Nodes: peak 1300k created 1416k lost 0
+
+ It also puts in the generated C or C++ file the number of tnodes
+ created for a rule (at the end of the rule). However this
+ information is not sufficient to locate the alternatives within
+ a rule which are causing the creation of tnodes.
+
+ Using:
+
+ antlr -treport 100000 ....
+
+ causes antlr to list on stdout any alternatives which require the
+ creation of more than 100,000 tnodes, along with the lookahead sets
+ for those alternatives.
+
+ The following is a trivial case from the ansi.g grammar which shows
+ the format of the report. This report might be of more interest
+ in cases where 1,000,000 tuples were created to resolve the ambiguity.
+
+ -------------------------------------------------------------------------
+ There were 0 tuples whose ambiguity could not be resolved
+ by full lookahead
+ There were 157 tnodes created to resolve ambiguity between:
+
+ Choice 1: statement/2 line 475 file ansi.g
+ Choice 2: statement/3 line 476 file ansi.g
+
+ Intersection of lookahead[1] sets:
+
+ IDENTIFIER
+
+ Intersection of lookahead[2] sets:
+
+ LPARENTHESIS COLON AMPERSAND MINUS
+ STAR PLUSPLUS MINUSMINUS ONESCOMPLEMENT
+ NOT SIZEOF OCTALINT DECIMALINT
+ HEXADECIMALINT FLOATONE FLOATTWO IDENTIFIER
+ STRING CHARACTER
+ -------------------------------------------------------------------------
+
+#145. (Documentation) Generation of Expression Trees
+
+ Item #99 was misleading because it implied that the optimization
+ for tree expressions was available only for trees created by
+ predicate expressions and neglected to mention that it required
+ the use of "-mrhoist on". The optimization applies to tree
+ expressions created for grammars with k>1 and for predicates with
+ lookahead depth >1.
+
+ In MR11 the optimized version is always used so the -mrhoist on
+ option need not be specified.
+
+#144. (Changed in MR11) Incorrect test for exception group
+
+ In testing for a rule's exception group the label a pointer
+ is compared against '\0'. The intention is "*pointer".
+
+ Reported by Jeffrey C. Fried (Jeff@Fried.net).
+
+#143. (Changed in MR11) Optional ";" at end of #token statement
+
+ Fixes problem of:
+
+ #token X "x"
+
+ <<
+ parser action
+ >>
+
+ Being confused with:
+
+ #token X "x" <<lexical action>>
+
+#142. (Changed in MR11) class BufFileInput subclass of DLGInputStream
+
+ Alexey Demakov (demakov@kazbek.ispras.ru) has supplied class
+ BufFileInput derived from DLGInputStream which provides a
+ function lookahead(char *string) to test characters in the
+ input stream more than one character ahead.
+
+ The default amount of lookahead is specified by the constructor
+ and defaults to 8 characters. This does *not* include the one
+ character of lookahead maintained internally by DLG in member "ch"
+ and which is not available for testing via BufFileInput::lookahead().
+
+ This is a useful class for overcoming the one-character-lookahead
+ limitation of DLG without resorting to a lexer capable of
+ backtracking (like flex) which is not integrated with antlr as is
+ DLG.
+
+ There are no restrictions on copying or using BufFileInput.* except
+ that the authorship and related information must be retained in the
+ source code.
+
+ The class is located in pccts/h/BufFileInput.* of the kit.
+
+#141. (Changed in MR11) ZZDEBUG_CONSUME for ANTLRParser::consume()
+
+ A debug aid has been added to file ANTLRParser::consume() in
+ file AParser.cpp:
+
+ #ifdef ZZDEBUG_CONSUME_ACTION
+ zzdebug_consume_action();
+ #endif
+
+ Suggested by Sramji Ramanathan (ps@kumaran.com).
+
+#140. (Changed in MR11) #pred to define predicates
+
+ +---------------------------------------------------+
+ | Note: Assume "-prc on" for this entire discussion |
+ +---------------------------------------------------+
+
+ A problem with predicates is that each one is regarded as
+ unique and capable of disambiguating cases where two
+ alternatives have identical lookahead. For example:
+
+ rule : <<pred(LATEXT(1))>>? A
+ | <<pred(LATEXT(1))>>? A
+ ;
+
+ will not cause any error messages or warnings to be issued
+ by earlier versions of pccts. To compare the text of the
+ predicates is an incomplete solution.
+
+ In 1.33MR11 I am introducing the #pred statement in order to
+ solve some problems with predicates. The #pred statement allows
+ one to give a symbolic name to a "predicate literal" or a
+ "predicate expression" in order to refer to it in other predicate
+ expressions or in the rules of the grammar.
+
+ The predicate literal associated with a predicate symbol is C
+ or C++ code which can be used to test the condition. A
+ predicate expression defines a predicate symbol in terms of other
+ predicate symbols using "!", "&&", and "||". A predicate symbol
+ can be defined in terms of a predicate literal, a predicate
+ expression, or *both*.
+
+ When a predicate symbol is defined with both a predicate literal
+ and a predicate expression, the predicate literal is used to generate
+ code, but the predicate expression is used to check for two
+ alternatives with identical predicates in both alternatives.
+
+ Here are some examples of #pred statements:
+
+ #pred IsLabel <<isLabel(LATEXT(1))>>?
+ #pred IsLocalVar <<isLocalVar(LATEXT(1))>>?
+ #pred IsGlobalVar <<isGlobalVar(LATEXT(1)>>?
+ #pred IsVar <<isVar(LATEXT(1))>>? IsLocalVar || IsGlobalVar
+ #pred IsScoped <<isScoped(LATEXT(1))>>? IsLabel || IsLocalVar
+
+ I hope that the use of EBNF notation to describe the syntax of the
+ #pred statement will not cause problems for my readers (joke).
+
+ predStatement : "#pred"
+ CapitalizedName
+ (
+ "<<predicate_literal>>?"
+ | "<<predicate_literal>>?" predOrExpr
+ | predOrExpr
+ )
+ ;
+
+ predOrExpr : predAndExpr ( "||" predAndExpr ) * ;
+
+ predAndExpr : predPrimary ( "&&" predPrimary ) * ;
+
+ predPrimary : CapitalizedName
+ | "!" predPrimary
+ | "(" predOrExpr ")"
+ ;
+
+ What is the purpose of this nonsense ?
+
+ To understand how predicate symbols help, you need to realize that
+ predicate symbols are used in two different ways with two different
+ goals.
+
+ a. Allow simplification of predicates which have been combined
+ during predicate hoisting.
+
+ b. Allow recognition of identical predicates which can't disambiguate
+ alternatives with common lookahead.
+
+ First we will discuss goal (a). Consider the following rule:
+
+ rule0: rule1
+ | ID
+ | ...
+ ;
+
+ rule1: rule2
+ | rule3
+ ;
+
+ rule2: <<isX(LATEXT(1))>>? ID ;
+ rule3: <<!isX(LATEXT(1)>>? ID ;
+
+ When the predicates in rule2 and rule3 are combined by hoisting
+ to create a prediction expression for rule1 the result is:
+
+ if ( LA(1)==ID
+ && ( isX(LATEXT(1) || !isX(LATEXT(1) ) ) { rule1(); ...
+
+ This is inefficient, but more importantly, can lead to false
+ assumptions that the predicate expression distinguishes the rule1
+ alternative with some other alternative with lookahead ID. In
+ MR11 one can write:
+
+ #pred IsX <<isX(LATEXT(1))>>?
+
+ ...
+
+ rule2: <<IsX>>? ID ;
+ rule3: <<!IsX>>? ID ;
+
+ During hoisting MR11 recognizes this as a special case and
+ eliminates the predicates. The result is a prediction
+ expression like the following:
+
+ if ( LA(1)==ID ) { rule1(); ...
+
+ Please note that the following cases which appear to be equivalent
+ *cannot* be simplified by MR11 during hoisting because the hoisting
+ logic only checks for a "!" in the predicate action, not in the
+ predicate expression for a predicate symbol.
+
+ *Not* equivalent and is not simplified during hoisting:
+
+ #pred IsX <<isX(LATEXT(1))>>?
+ #pred NotX <<!isX(LATEXT(1))>>?
+ ...
+ rule2: <<IsX>>? ID ;
+ rule3: <<NotX>>? ID ;
+
+ *Not* equivalent and is not simplified during hoisting:
+
+ #pred IsX <<isX(LATEXT(1))>>?
+ #pred NotX !IsX
+ ...
+ rule2: <<IsX>>? ID ;
+ rule3: <<NotX>>? ID ;
+
+ Now we will discuss goal (b).
+
+ When antlr discovers that there is a lookahead ambiguity between
+ two alternatives it attempts to resolve the ambiguity by searching
+ for predicates in both alternatives. In the past any predicate
+ would do, even if the same one appeared in both alternatives:
+
+ rule: <<p(LATEXT(1))>>? X
+ | <<p(LATEXT(1))>>? X
+ ;
+
+ The #pred statement is a start towards solving this problem.
+ During ambiguity resolution (*not* predicate hoisting) the
+ predicates for the two alternatives are expanded and compared.
+ Consider the following example:
+
+ #pred Upper <<isUpper(LATEXT(1))>>?
+ #pred Lower <<isLower(LATEXT(1))>>?
+ #pred Alpha <<isAlpha(LATEXT(1))>>? Upper || Lower
+
+ rule0: rule1
+ | <<Alpha>>? ID
+ ;
+
+ rule1:
+ | rule2
+ | rule3
+ ...
+ ;
+
+ rule2: <<Upper>>? ID;
+ rule3: <<Lower>>? ID;
+
+ The definition of #pred Alpha expresses:
+
+ a. to test the predicate use the C code "isAlpha(LATEXT(1))"
+
+ b. to analyze the predicate use the information that
+ Alpha is equivalent to the union of Upper and Lower,
+
+ During ambiguity resolution the definition of Alpha is expanded
+ into "Upper || Lower" and compared with the predicate in the other
+ alternative, which is also "Upper || Lower". Because they are
+ identical MR11 will report a problem.
+
+ -------------------------------------------------------------------------
+ t10.g, line 5: warning: the predicates used to disambiguate rule rule0
+ (file t10.g alt 1 line 5 and alt 2 line 6)
+ are identical when compared without context and may have no
+ resolving power for some lookahead sequences.
+ -------------------------------------------------------------------------
+
+ If you use the "-info p" option the output file will contain:
+
+ +----------------------------------------------------------------------+
+ |#if 0 |
+ | |
+ |The following predicates are identical when compared without |
+ | lookahead context information. For some ambiguous lookahead |
+ | sequences they may not have any power to resolve the ambiguity. |
+ | |
+ |Choice 1: rule0/1 alt 1 line 5 file t10.g |
+ | |
+ | The original predicate for choice 1 with available context |
+ | information: |
+ | |
+ | OR expr |
+ | |
+ | pred << Upper>>? |
+ | depth=k=1 rule rule2 line 14 t10.g |
+ | set context: |
+ | ID |
+ | |
+ | pred << Lower>>? |
+ | depth=k=1 rule rule3 line 15 t10.g |
+ | set context: |
+ | ID |
+ | |
+ | The predicate for choice 1 after expansion (but without context |
+ | information): |
+ | |
+ | OR expr |
+ | |
+ | pred << isUpper(LATEXT(1))>>? |
+ | depth=k=1 rule line 1 t10.g |
+ | |
+ | pred << isLower(LATEXT(1))>>? |
+ | depth=k=1 rule line 2 t10.g |
+ | |
+ | |
+ |Choice 2: rule0/2 alt 2 line 6 file t10.g |
+ | |
+ | The original predicate for choice 2 with available context |
+ | information: |
+ | |
+ | pred << Alpha>>? |
+ | depth=k=1 rule rule0 line 6 t10.g |
+ | set context: |
+ | ID |
+ | |
+ | The predicate for choice 2 after expansion (but without context |
+ | information): |
+ | |
+ | OR expr |
+ | |
+ | pred << isUpper(LATEXT(1))>>? |
+ | depth=k=1 rule line 1 t10.g |
+ | |
+ | pred << isLower(LATEXT(1))>>? |
+ | depth=k=1 rule line 2 t10.g |
+ | |
+ | |
+ |#endif |
+ +----------------------------------------------------------------------+
+
+ The comparison of the predicates for the two alternatives takes
+ place without context information, which means that in some cases
+ the predicates will be considered identical even though they operate
+ on disjoint lookahead sets. Consider:
+
+ #pred Alpha
+
+ rule1: <<Alpha>>? ID
+ | <<Alpha>>? Label
+ ;
+
+ Because the comparison of predicates takes place without context
+ these will be considered identical. The reason for comparing
+ without context is that otherwise it would be necessary to re-evaluate
+ the entire predicate expression for each possible lookahead sequence.
+ This would require more code to be written and more CPU time during
+ grammar analysis, and it is not yet clear whether anyone will even make
+ use of the new #pred facility.
+
+ A temporary workaround might be to use different #pred statements
+ for predicates you know have different context. This would avoid
+ extraneous warnings.
+
+ The above example might be termed a "false positive". Comparison
+ without context will also lead to "false negatives". Consider the
+ following example:
+
+ #pred Alpha
+ #pred Beta
+
+ rule1: <<Alpha>>? A
+ | rule2
+ ;
+
+ rule2: <<Alpha>>? A
+ | <<Beta>>? B
+ ;
+
+ The predicate used for alt 2 of rule1 is (Alpha || Beta). This
+ appears to be different than the predicate Alpha used for alt1.
+ However, the context of Beta is B. Thus when the lookahead is A
+ Beta will have no resolving power and Alpha will be used for both
+ alternatives. Using the same predicate for both alternatives isn't
+ very helpful, but this will not be detected with 1.33MR11.
+
+ To properly handle this the predicate expression would have to be
+ evaluated for each distinct lookahead context.
+
+ To determine whether two predicate expressions are identical is
+ difficult. The routine may fail to identify identical predicates.
+
+ The #pred feature also compares predicates to see if a choice between
+ alternatives which is resolved by a predicate which makes the second
+ choice unreachable. Consider the following example:
+
+ #pred A <<A(LATEXT(1)>>?
+ #pred B <<B(LATEXT(1)>>?
+ #pred A_or_B A || B
+
+ r : s
+ | t
+ ;
+ s : <<A_or_B>>? ID
+ ;
+ t : <<A>>? ID
+ ;
+
+ ----------------------------------------------------------------------------
+ t11.g, line 5: warning: the predicate used to disambiguate the
+ first choice of rule r
+ (file t11.g alt 1 line 5 and alt 2 line 6)
+ appears to "cover" the second predicate when compared without context.
+ The second predicate may have no resolving power for some lookahead
+ sequences.
+ ----------------------------------------------------------------------------
+
+#139. (Changed in MR11) Problem with -gp in C++ mode
+
+ The -gp option to add a prefix to rule names did not work in
+ C++ mode. This has been fixed.
+
+ Reported by Alexey Demakov (demakov@kazbek.ispras.ru).
+
+#138. (Changed in MR11) Additional makefiles for non-MSVC++ MS systems
+
+ Sramji Ramanathan (ps@kumaran.com) has supplied makefiles for
+ building antlr and dlg with Win95/NT development tools that
+ are not based on MSVC5. They are pccts/antlr/AntlrMS.mak and
+ pccts/dlg/DlgMS.mak.
+
+ The first line of the makefiles require a definition of PCCTS_HOME.
+
+ These are in additiion to the AntlrMSVC50.* and DlgMSVC50.*
+ supplied by Jeff Vincent (JVincent@novell.com).
+
+#137. (Changed in MR11) Token getType(), getText(), getLine() const members
+
+ --------------------------------------------------------------------
+ If you use ANTLRCommonToken this change probably does not affect you.
+ --------------------------------------------------------------------
+
+ For a long time it has bothered me that these accessor functions
+ in ANTLRAbstractToken were not const member functions. I have
+ refrained from changing them because it require users to modify
+ existing token class definitions which are derived directly
+ from ANTLRAbstractToken. I think it is now time.
+
+ For those who are not used to C++, a "const member function" is a
+ member function which does not modify its own object - the thing
+ to which "this" points. This is quite different from a function
+ which does not modify its arguments
+
+ Most token definitions based on ANTLRAbstractToken have something like
+ the following in order to create concrete definitions of the pure
+ virtual methods in ANTLRAbstractToken:
+
+ class MyToken : public ANTLRAbstractToken {
+ ...
+ ANTLRTokenType getType() {return _type; }
+ int getLine() {return _line; }
+ ANTLRChar * getText() {return _text; }
+ ...
+ }
+
+ The required change is simply to put "const" following the function
+ prototype in the header (.h file) and the definition file (.cpp if
+ it is not inline):
+
+ class MyToken : public ANTLRAbstractToken {
+ ...
+ ANTLRTokenType getType() const {return _type; }
+ int getLine() const {return _line; }
+ ANTLRChar * getText() const {return _text; }
+ ...
+ }
+
+ This was originally proposed a long time ago by Bruce
+ Guenter (bruceg@qcc.sk.ca).
+
+#136. (Changed in MR11) Added getLength() to ANTLRCommonToken
+
+ Classes ANTLRCommonToken and ANTLRCommonTokenNoRefCountToken
+ now have a member function:
+
+ int getLength() const { return strlen(getText()) }
+
+ Suggested by Sramji Ramanathan (ps@kumaran.com).
+
+#135. (Changed in MR11) Raised antlr's own default ZZLEXBUFSIZE to 8k
+
+#134a. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible
+
+ There is a typographical error in the definition of BITWISEOREQ:
+
+ #token BITWISEOREQ "!=" should be "\|="
+
+ When this change is combined with the bugfix to the follow set cache
+ problem (Item #147) and a minor rearrangement of the grammar
+ (Item #134b) it becomes a k=1 ck=2 grammar.
+
+#134b. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible
+
+ The following changes were made in the ansi.g grammar (along with
+ using -mrhoist on):
+
+ ansi.g
+ ======
+ void tracein(char *) ====> void tracein(const char *)
+ void traceout(char *) ====> void traceout(const char *)
+
+ <LT(1)->getType()==IDENTIFIER ? isTypeName(LT(1)->getText()) : 1>>?
+ ====> <<isTypeName(LT(1)->getText())>>?
+
+ <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \
+ isTypeName(LT(2)->getText()) : 1>>?
+ ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?
+
+ <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \
+ isTypeName(LT(2)->getText()) : 1>>?
+ ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?
+
+ added to init(): traceOptionValueDefault=0;
+ added to init(): traceOption(-1);
+
+ change rule "statement":
+
+ statement
+ : plain_label_statement
+ | case_label_statement
+ | <<;>> expression SEMICOLON
+ | compound_statement
+ | selection_statement
+ | iteration_statement
+ | jump_statement
+ | SEMICOLON
+ ;
+
+ plain_label_statement
+ : IDENTIFIER COLON statement
+ ;
+
+ case_label_statement
+ : CASE constant_expression COLON statement
+ | DEFAULT COLON statement
+ ;
+
+ support.cpp
+ ===========
+ void tracein(char *) ====> void tracein(const char *)
+ void traceout(char *) ====> void traceout(const char *)
+
+ added to tracein(): ANTLRParser::tracein(r); // call superclass method
+ added to traceout(): ANTLRParser::traceout(r); // call superclass method
+
+ Makefile
+ ========
+ added to AFLAGS: -mrhoist on -prc on
+
+#133. (Changed in 1.33MR11) Make trace options public in ANTLRParser
+
+ In checking T.J. Parr's ANSI C grammar for compatibility with
+ 1.33MR11 discovered that it was inconvenient to have the
+ trace facilities with protected access.
+
+#132. (Changed in 1.33MR11) Recognition of identical predicates in alts
+
+ Prior to 1.33MR11, there would be no ambiguity warning when the
+ very same predicate was used to disambiguate both alternatives:
+
+ test: ref B
+ | ref C
+ ;
+
+ ref : <<pred(LATEXT(1)>>? A
+
+ In 1.33MR11 this will cause the warning:
+
+ warning: the predicates used to disambiguate rule test
+ (file v98.g alt 1 line 1 and alt 2 line 2)
+ are identical and have no resolving power
+
+ ----------------- Note -----------------
+
+ This is different than the following case
+
+ test: <<pred(LATEXT(1))>>? A B
+ | <<pred(LATEXT(1)>>? A C
+ ;
+
+ In this case there are two distinct predicates
+ which have exactly the same text. In the first
+ example there are two references to the same
+ predicate. The problem represented by this
+ grammar will be addressed later.
+
+#131. (Changed in 1.33MR11) Case insensitive command line options
+
+ Command line switches like "-CC" and keywords like "on", "off",
+ and "stdin" are no longer case sensitive in antlr, dlg, and sorcerer.
+
+#130. (Changed in 1.33MR11) Changed ANTLR_VERSION to int from string
+
+ The ANTLR_VERSION was not an integer, making it difficult to
+ perform conditional compilation based on the antlr version.
+
+ Henceforth, ANTLR_VERSION will be:
+
+ (base_version * 10000) + release number
+
+ thus 1.33MR11 will be: 133*100+11 = 13311
+
+ Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE).
+
+#129. (Changed in 1.33MR11) Addition of ANTLR_VERSION to <parserName>.h
+
+ The following code is now inserted into <parserName>.h amd
+ stdpccts.h:
+
+ #ifndef ANTLR_VERSION
+ #define ANTLR_VERSION 13311
+ #endif
+
+ Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE)
+
+#128. (Changed in 1.33MR11) Redundant predicate code in (<<pred>>? ...)+
+
+ Prior to 1.33MR11, the following grammar would generate
+ redundant tests for the "while" condition.
+
+ rule2 : (<<pred>>? X)+ X
+ | B
+ ;
+
+ The code would resemble:
+
+ if (LA(1)==X) {
+ if (pred) {
+ do {
+ if (!pred) {zzfailed_pred(" pred");}
+ zzmatch(X); zzCONSUME;
+ } while (LA(1)==X && pred && pred);
+ } else {...
+
+ With 1.33MR11 the redundant predicate test is omitted.
+
+#127. (Changed in 1.33MR11)
+
+ Count Syntax Errors Count DLG Errors
+ ------------------- ----------------
+
+ C++ mode ANTLRParser:: DLGLexerBase::
+ syntaxErrCount lexErrCount
+ C mode zzSyntaxErrCount zzLexErrCount
+
+ The C mode variables are global and initialized to 0.
+ They are *not* reset to 0 automatically when antlr is
+ restarted.
+
+ The C++ mode variables are public. They are initialized
+ to 0 by the constructors. They are *not* reset to 0 by the
+ ANTLRParser::init() method.
+
+ Suggested by Reinier van den Born (reinier@vnet.ibm.com).
+
+#126. (Changed in 1.33MR11) Addition of #first <<...>>
+
+ The #first <<...>> inserts the specified text in the output
+ files before any other #include statements required by pccts.
+ The only things before the #first text are comments and
+ a #define ANTLR_VERSION.
+
+ Requested by and Esa Pulkkinen (esap@cs.tut.fi) and Alexin
+ Zoltan (alexin@inf.u-szeged.hu).
+
+#125. (Changed in 1.33MR11) Lookahead for (guard)? && <<p>>? predicates
+
+ When implementing the new style of guard predicate (Item #113)
+ in 1.33MR10 I decided to temporarily ignore the problem of
+ computing the "narrowest" lookahead context.
+
+ Consider the following k=1 grammar:
+
+ start : a
+ | b
+ ;
+
+ a : (A)? && <<pred1(LATEXT(1))>>? ab ;
+ b : (B)? && <<pred2(LATEXT(1))>>? ab ;
+
+ ab : A | B ;
+
+ In MR10 the context for both "a" and "b" was {A B} because this is
+ the first set of rule "ab". Normally, this is not a problem because
+ the predicate which follows the guard inhibits any ambiguity report
+ by antlr.
+
+ In MR11 the first set for rule "a" is {A} and for rule "b" it is {B}.
+
+#124. A Note on the New "&&" Style Guarded Predicates
+
+ I've been asked several times, "What is the difference between
+ the old "=>" style guard predicates and the new style "&&" guard
+ predicates, and how do you choose one over the other" ?
+
+ The main difference is that the "=>" does not apply the
+ predicate if the context guard doesn't match, whereas
+ the && form always does. What is the significance ?
+
+ If you have a predicate which is not on the "leading edge"
+ it cannot be hoisted. Suppose you need a predicate that
+ looks at LA(2). You must introduce it manually. The
+ classic example is:
+
+ castExpr :
+ LP typeName RP
+ | ....
+ ;
+
+ typeName : <<isTypeName(LATEXT(1))>>? ID
+ | STRUCT ID
+ ;
+
+ The problem is that typeName isn't on the leading edge
+ of castExpr, so the predicate isTypeName won't be hoisted into
+ castExpr to help make a decision on which production to choose.
+
+ The *first* attempt to fix it is this:
+
+ castExpr :
+ <<isTypeName(LATEXT(2))>>?
+ LP typeName RP
+ | ....
+ ;
+
+ Unfortunately, this won't work because it ignores
+ the problem of STRUCT. The solution is to apply
+ isTypeName() in castExpr if LA(2) is an ID and
+ don't apply it when LA(2) is STRUCT:
+
+ castExpr :
+ (LP ID)? => <<isTypeName(LATEXT(2))>>?
+ LP typeName RP
+ | ....
+ ;
+
+ In conclusion, the "=>" style guarded predicate is
+ useful when:
+
+ a. the tokens required for the predicate
+ are not on the leading edge
+ b. there are alternatives in the expression
+ selected by the predicate for which the
+ predicate is inappropriate
+
+ If (b) were false, then one could use a simple
+ predicate (assuming "-prc on"):
+
+ castExpr :
+ <<isTypeName(LATEXT(2))>>?
+ LP typeName RP
+ | ....
+ ;
+
+ typeName : <<isTypeName(LATEXT(1))>>? ID
+ ;
+
+ So, when do you use the "&&" style guarded predicate ?
+
+ The new-style "&&" predicate should always be used with
+ predicate context. The context guard is in ADDITION to
+ the automatically computed context. Thus it useful for
+ predicates which depend on the token type for reasons
+ other than context.
+
+ The following example is contributed by Reinier van den Born
+ (reinier@vnet.ibm.com).
+
+ +-------------------------------------------------------------------------+
+ | This grammar has two ways to call functions: |
+ | |
+ | - a "standard" call syntax with parens and comma separated args |
+ | - a shell command like syntax (no parens and spacing separated args) |
+ | |
+ | The former also allows a variable to hold the name of the function, |
+ | the latter can also be used to call external commands. |
+ | |
+ | The grammar (simplified) looks like this: |
+ | |
+ | fun_call : ID "(" { expr ("," expr)* } ")" |
+ | /* ID is function name */ |
+ | | "@" ID "(" { expr ("," expr)* } ")" |
+ | /* ID is var containing fun name */ |
+ | ; |
+ | |
+ | command : ID expr* /* ID is function name */ |
+ | | path expr* /* path is external command name */ |
+ | ; |
+ | |
+ | path : ID /* left out slashes and such */ |
+ | | "@" ID /* ID is environment var */ |
+ | ; |
+ | |
+ | expr : .... |
+ | | "(" expr ")"; |
+ | |
+ | call : fun_call |
+ | | command |
+ | ; |
+ | |
+ | Obviously the call is wildly ambiguous. This is more or less how this |
+ | is to be resolved: |
+ | |
+ | A call begins with an ID or an @ followed by an ID. |
+ | |
+ | If it is an ID and if it is an ext. command name -> command |
+ | if followed by a paren -> fun_call |
+ | otherwise -> command |
+ | |
+ | If it is an @ and if the ID is a var name -> fun_call |
+ | otherwise -> command |
+ | |
+ | One can implement these rules quite neatly using && predicates: |
+ | |
+ | call : ("@" ID)? && <<isVarName(LT(2))>>? fun_call |
+ | | (ID)? && <<isExtCmdName>>? command |
+ | | (ID "(")? fun_call |
+ | | command |
+ | ; |
+ | |
+ | This can be done better, so it is not an ideal example, but it |
+ | conveys the principle. |
+ +-------------------------------------------------------------------------+
+
+#123. (Changed in 1.33MR11) Correct definition of operators in ATokPtr.h
+
+ The return value of operators in ANTLRTokenPtr:
+
+ changed: unsigned ... operator !=(...)
+ to: int ... operator != (...)
+ changed: unsigned ... operator ==(...)
+ to: int ... operator == (...)
+
+ Suggested by R.A. Nelson (cowboy@VNET.IBM.COM)
+
+#122. (Changed in 1.33MR11) Member functions to reset DLG in C++ mode
+
+ void DLGFileReset(FILE *f) { input = f; found_eof = 0; }
+ void DLGStringReset(DLGChar *s) { input = s; p = &input[0]; }
+
+ Supplied by R.A. Nelson (cowboy@VNET.IBM.COM)
+
+#121. (Changed in 1.33MR11) Another attempt to fix -o (output dir) option
+
+ Another attempt is made to improve the -o option of antlr, dlg,
+ and sorcerer. This one by JVincent (JVincent@novell.com).
+
+ The current rule:
+
+ a. If -o is not specified than any explicit directory
+ names are retained.
+
+ b. If -o is specified than the -o directory name overrides any
+ explicit directory names.
+
+ c. The directory name of the grammar file is *not* stripped
+ to create the main output file. However it is stil subject
+ to override by the -o directory name.
+
+#120. (Changed in 1.33MR11) "-info f" output to stdout rather than stderr
+
+ Added option 0 (e.g. "-info 0") which is a noop.
+
+#119. (Changed in 1.33MR11) Ambiguity aid for grammars
+
+ The user can ask for additional information on ambiguities reported
+ by antlr to stdout. At the moment, only one ambiguity report can
+ be created in an antlr run.
+
+ This feature is enabled using the "-aa" (Ambiguity Aid) option.
+
+ The following options control the reporting of ambiguities:
+
+ -aa ruleName Selects reporting by name of rule
+ -aa lineNumber Selects reporting by line number
+ (file name not compared)
+
+ -aam Selects "multiple" reporting for a token
+ in the intersection set of the
+ alternatives.
+
+ For instance, the token ID may appear dozens
+ of times in various paths as the program
+ explores the rules which are reachable from
+ the point of an ambiguity. With option -aam
+ every possible path the search program
+ encounters is reported.
+
+ Without -aam only the first encounter is
+ reported. This may result in incomplete
+ information, but the information may be
+ sufficient and much shorter.
+
+ -aad depth Selects the depth of the search.
+ The default value is 1.
+
+ The number of paths to be searched, and the
+ size of the report can grow geometrically
+ with the -ck value if a full search for all
+ contributions to the source of the ambiguity
+ is explored.
+
+ The depth represents the number of tokens
+ in the lookahead set which are matched against
+ the set of ambiguous tokens. A depth of 1
+ means that the search stops when a lookahead
+ sequence of just one token is matched.
+
+ A k=1 ck=6 grammar might generate 5,000 items
+ in a report if a full depth 6 search is made
+ with the Ambiguity Aid. The source of the
+ problem may be in the first token and obscured
+ by the volume of data - I hesitate to call
+ it information.
+
+ When the user selects a depth > 1, the search
+ is first performed at depth=1 for both
+ alternatives, then depth=2 for both alternatives,
+ etc.
+
+ Sample output for rule grammar in antlr.g itself:
+
+ +---------------------------------------------------------------------+
+ | Ambiguity Aid |
+ | |
+ | Choice 1: grammar/70 line 632 file a.g |
+ | Choice 2: grammar/82 line 644 file a.g |
+ | |
+ | Intersection of lookahead[1] sets: |
+ | |
+ | "\}" "class" "#errclass" "#tokclass" |
+ | |
+ | Choice:1 Depth:1 Group:1 ("#errclass") |
+ | 1 in (...)* block grammar/70 line 632 a.g |
+ | 2 to error grammar/73 line 635 a.g |
+ | 3 error error/1 line 894 a.g |
+ | 4 #token "#errclass" error/2 line 895 a.g |
+ | |
+ | Choice:1 Depth:1 Group:2 ("#tokclass") |
+ | 2 to tclass grammar/74 line 636 a.g |
+ | 3 tclass tclass/1 line 937 a.g |
+ | 4 #token "#tokclass" tclass/2 line 938 a.g |
+ | |
+ | Choice:1 Depth:1 Group:3 ("class") |
+ | 2 to class_def grammar/75 line 637 a.g |
+ | 3 class_def class_def/1 line 669 a.g |
+ | 4 #token "class" class_def/3 line 671 a.g |
+ | |
+ | Choice:1 Depth:1 Group:4 ("\}") |
+ | 2 #token "\}" grammar/76 line 638 a.g |
+ | |
+ | Choice:2 Depth:1 Group:5 ("#errclass") |
+ | 1 in (...)* block grammar/83 line 645 a.g |
+ | 2 to error grammar/93 line 655 a.g |
+ | 3 error error/1 line 894 a.g |
+ | 4 #token "#errclass" error/2 line 895 a.g |
+ | |
+ | Choice:2 Depth:1 Group:6 ("#tokclass") |
+ | 2 to tclass grammar/94 line 656 a.g |
+ | 3 tclass tclass/1 line 937 a.g |
+ | 4 #token "#tokclass" tclass/2 line 938 a.g |
+ | |
+ | Choice:2 Depth:1 Group:7 ("class") |
+ | 2 to class_def grammar/95 line 657 a.g |
+ | 3 class_def class_def/1 line 669 a.g |
+ | 4 #token "class" class_def/3 line 671 a.g |
+ | |
+ | Choice:2 Depth:1 Group:8 ("\}") |
+ | 2 #token "\}" grammar/96 line 658 a.g |
+ +---------------------------------------------------------------------+
+
+ For a linear lookahead set ambiguity (where k=1 or for k>1 but
+ when all lookahead sets [i] with i<k all have degree one) the
+ reports appear in the following order:
+
+ for (depth=1 ; depth <= "-aad depth" ; depth++) {
+ for (alternative=1; alternative <=2 ; alternative++) {
+ while (matches-are-found) {
+ group++;
+ print-report
+ };
+ };
+ };
+
+ For reporting a k-tuple ambiguity, the reports appear in the
+ following order:
+
+ for (depth=1 ; depth <= "-aad depth" ; depth++) {
+ while (matches-are-found) {
+ for (alternative=1; alternative <=2 ; alternative++) {
+ group++;
+ print-report
+ };
+ };
+ };
+
+ This is because matches are generated in different ways for
+ linear lookahead and k-tuples.
+
+#118. (Changed in 1.33MR11) DEC VMS makefile and VMS related changes
+
+ Revised makefiles for DEC/VMS operating system for antlr, dlg,
+ and sorcerer.
+
+ Reduced names of routines with external linkage to less than 32
+ characters to conform to DEC/VMS linker limitations.
+
+ Jean-Francois Pieronne discovered problems with dlg and antlr
+ due to the VMS linker not being case sensitive for names with
+ external linkage. In dlg the problem was with "className" and
+ "ClassName". In antlr the problem was with "GenExprSets" and
+ "genExprSets".
+
+ Added genmms, a version of genmk for the DEC/VMS version of make.
+ The source is in directory pccts/support/DECmms.
+
+ All VMS contributions by Jean-Francois Pieronne (jfp@iname.com).
+
+#117. (Changed in 1.33MR10) new EXPERIMENTAL predicate hoisting code
+
+ The hoisting of predicates into rules to create prediction
+ expressions is a problem in antlr. Consider the following
+ example (k=1 with -prc on):
+
+ start : (a)* "@" ;
+ a : b | c ;
+ b : <<isUpper(LATEXT(1))>>? A ;
+ c : A ;
+
+ Prior to 1.33MR10 the code generated for "start" would resemble:
+
+ while {
+ if (LA(1)==A &&
+ (!LA(1)==A || isUpper())) {
+ a();
+ }
+ };
+
+ This code is wrong because it makes rule "c" unreachable from
+ "start". The essence of the problem is that antlr fails to
+ recognize that there can be a valid alternative within "a" even
+ when the predicate <<isUpper(LATEXT(1))>>? is false.
+
+ In 1.33MR10 with -mrhoist the hoisting of the predicate into
+ "start" is suppressed because it recognizes that "c" can
+ cover all the cases where the predicate is false:
+
+ while {
+ if (LA(1)==A) {
+ a();
+ }
+ };
+
+ With the antlr "-info p" switch the user will receive information
+ about the predicate suppression in the generated file:
+
+ --------------------------------------------------------------
+ #if 0
+
+ Hoisting of predicate suppressed by alternative without predicate.
+ The alt without the predicate includes all cases where
+ the predicate is false.
+
+ WITH predicate: line 7 v1.g
+ WITHOUT predicate: line 7 v1.g
+
+ The context set for the predicate:
+
+ A
+
+ The lookahead set for the alt WITHOUT the semantic predicate:
+
+ A
+
+ The predicate:
+
+ pred << isUpper(LATEXT(1))>>?
+ depth=k=1 rule b line 9 v1.g
+ set context:
+ A
+ tree context: null
+
+ Chain of referenced rules:
+
+ #0 in rule start (line 5 v1.g) to rule a
+ #1 in rule a (line 7 v1.g)
+
+ #endif
+ --------------------------------------------------------------
+
+ A predicate can be suppressed by a combination of alternatives
+ which, taken together, cover a predicate:
+
+ start : (a)* "@" ;
+
+ a : b | ca | cb | cc ;
+
+ b : <<isUpper(LATEXT(1))>>? ( A | B | C ) ;
+
+ ca : A ;
+ cb : B ;
+ cc : C ;
+
+ Consider a more complex example in which "c" covers only part of
+ a predicate:
+
+ start : (a)* "@" ;
+
+ a : b
+ | c
+ ;
+
+ b : <<isUpper(LATEXT(1))>>?
+ ( A
+ | X
+ );
+
+ c : A
+ ;
+
+ Prior to 1.33MR10 the code generated for "start" would resemble:
+
+ while {
+ if ( (LA(1)==A || LA(1)==X) &&
+ (! (LA(1)==A || LA(1)==X) || isUpper()) {
+ a();
+ }
+ };
+
+ With 1.33MR10 and -mrhoist the predicate context is restricted to
+ the non-covered lookahead. The code resembles:
+
+ while {
+ if ( (LA(1)==A || LA(1)==X) &&
+ (! (LA(1)==X) || isUpper()) {
+ a();
+ }
+ };
+
+ With the antlr "-info p" switch the user will receive information
+ about the predicate restriction in the generated file:
+
+ --------------------------------------------------------------
+ #if 0
+
+ Restricting the context of a predicate because of overlap
+ in the lookahead set between the alternative with the
+ semantic predicate and one without
+ Without this restriction the alternative without the predicate
+ could not be reached when input matched the context of the
+ predicate and the predicate was false.
+
+ WITH predicate: line 11 v4.g
+ WITHOUT predicate: line 12 v4.g
+
+ The original context set for the predicate:
+
+ A X
+
+ The lookahead set for the alt WITHOUT the semantic predicate:
+
+ A
+
+ The intersection of the two sets
+
+ A
+
+ The original predicate:
+
+ pred << isUpper(LATEXT(1))>>?
+ depth=k=1 rule b line 15 v4.g
+ set context:
+ A X
+ tree context: null
+
+ The new (modified) form of the predicate:
+
+ pred << isUpper(LATEXT(1))>>?
+ depth=k=1 rule b line 15 v4.g
+ set context:
+ X
+ tree context: null
+
+ #endif
+ --------------------------------------------------------------
+
+ The bad news about -mrhoist:
+
+ (a) -mrhoist does not analyze predicates with lookahead
+ depth > 1.
+
+ (b) -mrhoist does not look past a guarded predicate to
+ find context which might cover other predicates.
+
+ For these cases you might want to use syntactic predicates.
+ When a semantic predicate fails during guess mode the guess
+ fails and the next alternative is tried.
+
+ Limitation (a) is illustrated by the following example:
+
+ start : (stmt)* EOF ;
+
+ stmt : cast
+ | expr
+ ;
+ cast : <<isTypename(LATEXT(2))>>? LP ID RP ;
+
+ expr : LP ID RP ;
+
+ This is not much different from the first example, except that
+ it requires two tokens of lookahead context to determine what
+ to do. This predicate is NOT suppressed because the current version
+ is unable to handle predicates with depth > 1.
+
+ A predicate can be combined with other predicates during hoisting.
+ In those cases the depth=1 predicates are still handled. Thus,
+ in the following example the isUpper() predicate will be suppressed
+ by line #4 when hoisted from "bizarre" into "start", but will still
+ be present in "bizarre" in order to predict "stmt".
+
+ start : (bizarre)* EOF ; // #1
+ // #2
+ bizarre : stmt // #3
+ | A // #4
+ ;
+
+ stmt : cast
+ | expr
+ ;
+
+ cast : <<isTypename(LATEXT(2))>>? LP ID RP ;
+
+ expr : LP ID RP ;
+ | <<isUpper(LATEXT(1))>>? A
+
+ Limitation (b) is illustrated by the following example of a
+ context guarded predicate:
+
+ rule : (A)? <<p>>? // #1
+ (A // #2
+ |B // #3
+ ) // #4
+ | <<q>> B // #5
+ ;
+
+ Recall that this means that when the lookahead is NOT A then
+ the predicate "p" is ignored and it attempts to match "A|B".
+ Ideally, the "B" at line #3 should suppress predicate "q".
+ However, the current version does not attempt to look past
+ the guard predicate to find context which might suppress other
+ predicates.
+
+ In some cases -mrhoist will lead to the reporting of ambiguities
+ which were not visible before:
+
+ start : (a)* "@";
+ a : bc | d;
+ bc : b | c ;
+
+ b : <<isUpper(LATEXT(1))>>? A;
+ c : A ;
+
+ d : A ;
+
+ In this case there is a true ambiguity in "a" between "bc" and "d"
+ which can both match "A". Without -mrhoist the predicate in "b"
+ is hoisted into "a" and there is no ambiguity reported. However,
+ with -mrhoist, the predicate in "b" is suppressed by "c" (as it
+ should be) making the ambiguity in "a" apparent.
+
+ The motivations for these changes were hoisting problems reported
+ by Reinier van den Born (reinier@vnet.ibm.com) and several others.
+
+#116. (Changed in 1.33MR10) C++ mode: tracein/traceout rule name is (const char *)
+
+ The prototype for C++ mode routine tracein (and traceout) has changed from
+ "char *" to "const char *".
+
+#115. (Changed in 1.33MR10) Using guess mode with exception handlers in C mode
+
+ The definition of the C mode macros zzmatch_wsig and zzsetmatch_wsig
+ neglected to consider guess mode. When control passed to the rule's
+ parse exception handler the routine would exit without ever closing the
+ guess block. This would lead to unpredictable behavior.
+
+ In 1.33MR10 the behavior of exceptions in C mode and C++ mode should be
+ identical.
+
+#114. (Changed in 1.33MR10) difference in [zz]resynch() between C and C++ modes
+
+ There was a slight difference in the way C and C++ mode resynchronized
+ following a parsing error. The C routine would sometimes skip an extra
+ token before attempting to resynchronize.
+
+ The C routine was changed to match the C++ routine.
+
+#113. (Changed in 1.33MR10) new context guarded pred: (g)? && <<p>>? expr
+
+ The existing context guarded predicate:
+
+ rule : (guard)? => <<p>>? expr
+ | next_alternative
+ ;
+
+ generates code which resembles:
+
+ if (lookahead(expr) && (!guard || pred)) {
+ expr()
+ } else ....
+
+ This is not suitable for some applications because it allows
+ expr() to be invoked when the predicate is false. This is
+ intentional because it is meant to mimic automatically computed
+ predicate context.
+
+ The new context guarded predicate uses the guard information
+ differently because it has a different goal. Consider:
+
+ rule : (guard)? && <<p>>? expr
+ | next_alternative
+ ;
+
+ The new style of context guarded predicate is equivalent to:
+
+ rule : <<guard==true && pred>>? expr
+ | next_alternative
+ ;
+
+ It generates code which resembles:
+
+ if (lookahead(expr) && guard && pred) {
+ expr();
+ } else ...
+
+ Both forms of guarded predicates severely restrict the form of
+ the context guard: it can contain no rule references, no
+ (...)*, no (...)+, and no {...}. It may contain token and
+ token class references, and alternation ("|").
+
+ Addition for 1.33MR11: in the token expression all tokens must
+ be at the same height of the token tree:
+
+ (A ( B | C))? && ... is ok (all height 2)
+ (A ( B | ))? && ... is not ok (some 1, some 2)
+ (A B C D | E F G H)? && ... is ok (all height 4)
+ (A B C D | E )? && ... is not ok (some 4, some 1)
+
+ This restriction is required in order to properly compute the lookahead
+ set for expressions like:
+
+ rule1 : (A B C)? && <<pred>>? rule2 ;
+ rule2 : (A|X) (B|Y) (C|Z);
+
+ This addition was suggested by Rienier van den Born (reinier@vnet.ibm.com)
+
+#112. (Changed in 1.33MR10) failed validation predicate in C guess mode
+
+ John Lilley (jlilley@empathy.com) suggested that failed validation
+ predicates abort a guess rather than reporting a failed error.
+ This was installed in C++ mode (Item #4). Only now was it noticed
+ that the fix was never installed for C mode.
+
+#111. (Changed in 1.33MR10) moved zzTRACEIN to before init action
+
+ When the antlr -gd switch is present antlr generates calls to
+ zzTRACEIN at the start of a rule and zzTRACEOUT at the exit
+ from a rule. Prior to 1.33MR10 Tthe call to zzTRACEIN was
+ after the init-action, which could cause confusion because the
+ init-actions were reported with the name of the enclosing rule,
+ rather than the active rule.
+
+#110. (Changed in 1.33MR10) antlr command line copied to generated file
+
+ The antlr command line is now copied to the generated file near
+ the start.
+
+#109. (Changed in 1.33MR10) improved trace information
+
+ The quality of the trace information provided by the "-gd"
+ switch has been improved significantly. Here is an example
+ of the output from a test program. It shows the rule name,
+ the first token of lookahead, the call depth, and the guess
+ status:
+
+ exit rule gusxx {"?"} depth 2
+ enter rule gusxx {"?"} depth 2
+ enter rule gus1 {"o"} depth 3 guessing
+ guess done - returning to rule gus1 {"o"} at depth 3
+ (guess mode continues - an enclosing guess is still active)
+ guess done - returning to rule gus1 {"Z"} at depth 3
+ (guess mode continues - an enclosing guess is still active)
+ exit rule gus1 {"Z"} depth 3 guessing
+ guess done - returning to rule gusxx {"o"} at depth 2 (guess mode ends)
+ enter rule gus1 {"o"} depth 3
+ guess done - returning to rule gus1 {"o"} at depth 3 (guess mode ends)
+ guess done - returning to rule gus1 {"Z"} at depth 3 (guess mode ends)
+ exit rule gus1 {"Z"} depth 3
+ line 1: syntax error at "Z" missing SC
+ ...
+
+ Rule trace reporting is controlled by the value of the integer
+ [zz]traceOptionValue: when it is positive tracing is enabled,
+ otherwise it is disabled. Tracing during guess mode is controlled
+ by the value of the integer [zz]traceGuessOptionValue. When
+ it is positive AND [zz]traceOptionValue is positive rule trace
+ is reported in guess mode.
+
+ The values of [zz]traceOptionValue and [zz]traceGuessOptionValue
+ can be adjusted by subroutine calls listed below.
+
+ Depending on the presence or absence of the antlr -gd switch
+ the variable [zz]traceOptionValueDefault is set to 0 or 1. When
+ the parser is initialized or [zz]traceReset() is called the
+ value of [zz]traceOptionValueDefault is copied to [zz]traceOptionValue.
+ The value of [zz]traceGuessOptionValue is always initialzed to 1,
+ but, as noted earlier, nothing will be reported unless
+ [zz]traceOptionValue is also positive.
+
+ When the parser state is saved/restored the value of the trace
+ variables are also saved/restored. If a restore causes a change in
+ reporting behavior from on to off or vice versa this will be reported.
+
+ When the -gd option is selected, the macro "#define zzTRACE_RULES"
+ is added to appropriate output files.
+
+ C++ mode
+ --------
+ int traceOption(int delta)
+ int traceGuessOption(int delta)
+ void traceReset()
+ int traceOptionValueDefault
+
+ C mode
+ --------
+ int zzTraceOption(int delta)
+ int zzTraceGuessOption(int delta)
+ void zzTraceReset()
+ int zzTraceOptionValueDefault
+
+ The argument "delta" is added to the traceOptionValue. To
+ turn on trace when inside a particular rule one:
+
+ rule : <<traceOption(+1);>>
+ (
+ rest-of-rule
+ )
+ <<traceOption(-1);>>
+ ; /* fail clause */ <<traceOption(-1);>>
+
+ One can use the same idea to turn *off* tracing within a
+ rule by using a delta of (-1).
+
+ An improvement in the rule trace was suggested by Sramji
+ Ramanathan (ps@kumaran.com).
+
+#108. A Note on Deallocation of Variables Allocated in Guess Mode
+
+ NOTE
+ ------------------------------------------------------
+ This mechanism only works for heap allocated variables
+ ------------------------------------------------------
+
+ The rewrite of the trace provides the machinery necessary
+ to properly free variables or undo actions following a
+ failed guess.
+
+ The macro zzUSER_GUESS_HOOK(guessSeq,zzrv) is expanded
+ as part of the zzGUESS macro. When a guess is opened
+ the value of zzrv is 0. When a longjmp() is executed to
+ undo the guess, the value of zzrv will be 1.
+
+ The macro zzUSER_GUESS_DONE_HOOK(guessSeq) is expanded
+ as part of the zzGUESS_DONE macro. This is executed
+ whether the guess succeeds or fails as part of closing
+ the guess.
+
+ The guessSeq is a sequence number which is assigned to each
+ guess and is incremented by 1 for each guess which becomes
+ active. It is needed by the user to associate the start of
+ a guess with the failure and/or completion (closing) of a
+ guess.
+
+ Guesses are nested. They must be closed in the reverse
+ of the order that they are opened.
+
+ In order to free memory used by a variable during a guess
+ a user must write a routine which can be called to
+ register the variable along with the current guess sequence
+ number provided by the zzUSER_GUESS_HOOK macro. If the guess
+ fails, all variables tagged with the corresponding guess
+ sequence number should be released. This is ugly, but
+ it would require a major rewrite of antlr 1.33 to use
+ some mechanism other than setjmp()/longjmp().
+
+ The order of calls for a *successful* guess would be:
+
+ zzUSER_GUESS_HOOK(guessSeq,0);
+ zzUSER_GUESS_DONE_HOOK(guessSeq);
+
+ The order of calls for a *failed* guess would be:
+
+ zzUSER_GUESS_HOOK(guessSeq,0);
+ zzUSER_GUESS_HOOK(guessSeq,1);
+ zzUSER_GUESS_DONE_HOOK(guessSeq);
+
+ The default definitions of these macros are empty strings.
+
+ Here is an example in C++ mode. The zzUSER_GUESS_HOOK and
+ zzUSER_GUESS_DONE_HOOK macros and myGuessHook() routine
+ can be used without change in both C and C++ versions.
+
+ ----------------------------------------------------------------------
+ <<
+
+ #include "AToken.h"
+
+ typedef ANTLRCommonToken ANTLRToken;
+
+ #include "DLGLexer.h"
+
+ int main() {
+
+ {
+ DLGFileInput in(stdin);
+ DLGLexer lexer(&in,2000);
+ ANTLRTokenBuffer pipe(&lexer,1);
+ ANTLRCommonToken aToken;
+ P parser(&pipe);
+
+ lexer.setToken(&aToken);
+ parser.init();
+ parser.start();
+ };
+
+ fclose(stdin);
+ fclose(stdout);
+ return 0;
+ }
+
+ >>
+
+ <<
+ char *s=NULL;
+
+ #undef zzUSER_GUESS_HOOK
+ #define zzUSER_GUESS_HOOK(guessSeq,zzrv) myGuessHook(guessSeq,zzrv);
+ #undef zzUSER_GUESS_DONE_HOOK
+ #define zzUSER_GUESS_DONE_HOOK(guessSeq) myGuessHook(guessSeq,2);
+
+ void myGuessHook(int guessSeq,int zzrv) {
+ if (zzrv == 0) {
+ fprintf(stderr,"User hook: starting guess #%d\n",guessSeq);
+ } else if (zzrv == 1) {
+ free (s);
+ s=NULL;
+ fprintf(stderr,"User hook: failed guess #%d\n",guessSeq);
+ } else if (zzrv == 2) {
+ free (s);
+ s=NULL;
+ fprintf(stderr,"User hook: ending guess #%d\n",guessSeq);
+ };
+ }
+
+ >>
+
+ #token A "a"
+ #token "[\t \ \n]" <<skip();>>
+
+ class P {
+
+ start : (top)+
+ ;
+
+ top : (which) ? <<fprintf(stderr,"%s is a which\n",s); free(s); s=NULL; >>
+ | other <<fprintf(stderr,"%s is an other\n",s); free(s); s=NULL; >>
+ ; <<if (s != NULL) free(s); s=NULL; >>
+
+ which : which2
+ ;
+
+ which2 : which3
+ ;
+ which3
+ : (label)? <<fprintf(stderr,"%s is a label\n",s);>>
+ | (global)? <<fprintf(stderr,"%s is a global\n",s);>>
+ | (exclamation)? <<fprintf(stderr,"%s is an exclamation\n",s);>>
+ ;
+
+ label : <<s=strdup(LT(1)->getText());>> A ":" ;
+
+ global : <<s=strdup(LT(1)->getText());>> A "::" ;
+
+ exclamation : <<s=strdup(LT(1)->getText());>> A "!" ;
+
+ other : <<s=strdup(LT(1)->getText());>> "other" ;
+
+ }
+ ----------------------------------------------------------------------
+
+ This is a silly example, but illustrates the idea. For the input
+ "a ::" with tracing enabled the output begins:
+
+ ----------------------------------------------------------------------
+ enter rule "start" depth 1
+ enter rule "top" depth 2
+ User hook: starting guess #1
+ enter rule "which" depth 3 guessing
+ enter rule "which2" depth 4 guessing
+ enter rule "which3" depth 5 guessing
+ User hook: starting guess #2
+ enter rule "label" depth 6 guessing
+ guess failed
+ User hook: failed guess #2
+ guess done - returning to rule "which3" at depth 5 (guess mode continues
+ - an enclosing guess is still active)
+ User hook: ending guess #2
+ User hook: starting guess #3
+ enter rule "global" depth 6 guessing
+ exit rule "global" depth 6 guessing
+ guess done - returning to rule "which3" at depth 5 (guess mode continues
+ - an enclosing guess is still active)
+ User hook: ending guess #3
+ enter rule "global" depth 6 guessing
+ exit rule "global" depth 6 guessing
+ exit rule "which3" depth 5 guessing
+ exit rule "which2" depth 4 guessing
+ exit rule "which" depth 3 guessing
+ guess done - returning to rule "top" at depth 2 (guess mode ends)
+ User hook: ending guess #1
+ enter rule "which" depth 3
+ .....
+ ----------------------------------------------------------------------
+
+ Remember:
+
+ (a) Only init-actions are executed during guess mode.
+ (b) A rule can be invoked multiple times during guess mode.
+ (c) If the guess succeeds the rule will be called once more
+ without guess mode so that normal actions will be executed.
+ This means that the init-action might need to distinguish
+ between guess mode and non-guess mode using the variable
+ [zz]guessing.
+
+#107. (Changed in 1.33MR10) construction of ASTs in guess mode
+
+ Prior to 1.33MR10, when using automatic AST construction in C++
+ mode for a rule, an AST would be constructed for elements of the
+ rule even while in guess mode. In MR10 this no longer occurs.
+
+#106. (Changed in 1.33MR10) guess variable confusion
+
+ In C++ mode a guess which failed always restored the parser state
+ using zzGUESS_DONE as part of zzGUESS_FAIL. Prior to 1.33MR10,
+ C mode required an explicit call to zzGUESS_DONE after the
+ call to zzGUESS_FAIL.
+
+ Consider:
+
+ rule : (alpha)? beta
+ | ...
+ ;
+
+ The generated code resembles:
+
+ zzGUESS
+ if (!zzrv && LA(1)==ID) { <==== line #1
+ alpha
+ zzGUESS_DONE
+ beta
+ } else {
+ if (! zzrv) zzGUESS_DONE <==== line #2a
+ ....
+
+ However, in some cases line #2 was rendered:
+
+ if (guessing) zzGUESS_DONE <==== line #2b
+
+ This would work for simple test cases, but would fail in
+ some cases where there was a guess while another guess was active.
+ One kind of failure would be to match up the zzGUESS_DONE at line
+ #2b with the "outer" guess which was still active. The outer
+ guess would "succeed" when only the inner guess should have
+ succeeded.
+
+ In 1.33MR10 the behavior of zzGUESS and zzGUESS_FAIL in C and
+ and C++ mode should be identical.
+
+ The same problem appears in 1.33 vanilla in some places. For
+ example:
+
+ start : { (sub)? } ;
+
+ or:
+
+ start : (
+ B
+ | ( sub )?
+ | C
+ )+
+ ;
+
+ generates incorrect code.
+
+ The general principle is:
+
+ (a) use [zz]guessing only when deciding between a call to zzFAIL
+ or zzGUESS_FAIL
+
+ (b) use zzrv in all other cases
+
+ This problem was discovered while testing changes to item #105.
+ I believe this is now fixed. My apologies.
+
+#105. (Changed in 1.33MR10) guess block as single alt of (...)+
+
+ Prior to 1.33MR10 the following constructs:
+
+ rule_plus : (
+ (sub)?
+ )+
+ ;
+
+ rule_star : (
+ (sub)?
+ )*
+ ;
+
+ generated incorrect code for the guess block (which could result
+ in runtime errors) because of an incorrect optimization of a
+ block with only a single alternative.
+
+ The fix caused some changes to the fix described in Item #49
+ because there are now three code generation sequences for (...)+
+ blocks containing a guess block:
+
+ a. single alternative which is a guess block
+ b. multiple alternatives in which the last is a guess block
+ c. all other cases
+
+ Forms like "rule_star" can have unexpected behavior when there
+ is a syntax error: if the subrule "sub" is not matched *exactly*
+ then "rule_star" will consume no tokens.
+
+ Reported by Esa Pulkkinen (esap@cs.tut.fi).
+
+#104. (Changed in 1.33MR10) -o option for dlg
+
+ There was problem with the code added by item #74 to handle the
+ -o option of dlg. This should fix it.
+
+#103. (Changed in 1.33MR10) ANDed semantic predicates
+
+ Rescinded.
+
+ The optimization was a mistake.
+ The resulting problem is described in Item #150.
+
+#102. (Changed in 1.33MR10) allow "class parser : .... {"
+
+ The syntax of the class statement ("class parser-name {")
+ has been extended to allow for the specification of base
+ classes. An arbirtrary number of tokens may now appear
+ between the class name and the "{". They are output
+ again when the class declaration is generated. For
+ example:
+
+ class Parser : public MyBaseClassANTLRparser {
+
+ This was suggested by a user, but I don't have a record
+ of who it was.
+
+#101. (Changed in 1.33MR10) antlr -info command line switch
+
+ -info
+
+ p - extra predicate information in generated file
+
+ t - information about tnode use:
+ at the end of each rule in generated file
+ summary on stderr at end of program
+
+ m - monitor progress
+ prints name of each rule as it is started
+ flushes output at start of each rule
+
+ f - first/follow set information to stdout
+
+ 0 - no operation (added in 1.33MR11)
+
+ The options may be combined and may appear in any order.
+ For example:
+
+ antlr -info ptm -CC -gt -mrhoist on mygrammar.g
+
+#100a. (Changed in 1.33MR10) Predicate tree simplification
+
+ When the same predicates can be referenced in more than one
+ alternative of a block large predicate trees can be formed.
+
+ The difference that these optimizations make is so dramatic
+ that I have decided to use it even when -mrhoist is not selected.
+
+ Consider the following grammar:
+
+ start : ( all )* ;
+
+ all : a
+ | d
+ | e
+ | f
+ ;
+
+ a : c A B
+ | c A C
+ ;
+
+ c : <<AAA(LATEXT(2))>>?
+ ;
+
+ d : <<BBB(LATEXT(2))>>? B C
+ ;
+
+ e : <<CCC(LATEXT(2))>>? B C
+ ;
+
+ f : e X Y
+ ;
+
+ In rule "a" there is a reference to rule "c" in both alternatives.
+ The length of the predicate AAA is k=2 and it can be followed in
+ alternative 1 only by (A B) while in alternative 2 it can be
+ followed only by (A C). Thus they do not have identical context.
+
+ In rule "all" the alternatives which refer to rules "e" and "f" allow
+ elimination of the duplicate reference to predicate CCC.
+
+ The table below summarized the kind of simplification performed by
+ 1.33MR10. In the table, X and Y stand for single predicates
+ (not trees).
+
+ (OR X (OR Y (OR Z))) => (OR X Y Z)
+ (AND X (AND Y (AND Z))) => (AND X Y Z)
+
+ (OR X (... (OR X Y) ... )) => (OR X (... Y ... ))
+ (AND X (... (AND X Y) ... )) => (AND X (... Y ... ))
+ (OR X (... (AND X Y) ... )) => (OR X (... ... ))
+ (AND X (... (OR X Y) ... )) => (AND X (... ... ))
+
+ (AND X) => X
+ (OR X) => X
+
+ In a test with a complex grammar for a real application, a predicate
+ tree with six OR nodes and 12 leaves was reduced to "(OR X Y Z)".
+
+ In 1.33MR10 there is a greater effort to release memory used
+ by predicates once they are no longer in use.
+
+#100b. (Changed in 1.33MR10) Suppression of extra predicate tests
+
+ The following optimizations require that -mrhoist be selected.
+
+ It is relatively easy to optimize the code generated for predicate
+ gates when they are of the form:
+
+ (AND X Y Z ...)
+ or (OR X Y Z ...)
+
+ where X, Y, Z, and "..." represent individual predicates (leaves) not
+ predicate trees.
+
+ If the predicate is an AND the contexts of the X, Y, Z, etc. are
+ ANDed together to create a single Tree context for the group and
+ context tests for the individual predicates are suppressed:
+
+ --------------------------------------------------
+ Note: This was incorrect. The contexts should be
+ ORed together. This has been fixed. A more
+ complete description is available in item #152.
+ ---------------------------------------------------
+
+ Optimization 1: (AND X Y Z ...)
+
+ Suppose the context for Xtest is LA(1)==LP and the context for
+ Ytest is LA(1)==LP && LA(2)==ID.
+
+ Without the optimization the code would resemble:
+
+ if (lookaheadContext &&
+ !(LA(1)==LP && LA(1)==LP && LA(2)==ID) ||
+ ( (! LA(1)==LP || Xtest) &&
+ (! (LA(1)==LP || LA(2)==ID) || Xtest)
+ )) {...
+
+ With the -mrhoist optimization the code would resemble:
+
+ if (lookaheadContext &&
+ ! (LA(1)==LP && LA(2)==ID) || (Xtest && Ytest) {...
+
+ Optimization 2: (OR X Y Z ...) with identical contexts
+
+ Suppose the context for Xtest is LA(1)==ID and for Ytest
+ the context is also LA(1)==ID.
+
+ Without the optimization the code would resemble:
+
+ if (lookaheadContext &&
+ ! (LA(1)==ID || LA(1)==ID) ||
+ (LA(1)==ID && Xtest) ||
+ (LA(1)==ID && Ytest) {...
+
+ With the -mrhoist optimization the code would resemble:
+
+ if (lookaheadContext &&
+ (! LA(1)==ID) || (Xtest || Ytest) {...
+
+ Optimization 3: (OR X Y Z ...) with distinct contexts
+
+ Suppose the context for Xtest is LA(1)==ID and for Ytest
+ the context is LA(1)==LP.
+
+ Without the optimization the code would resemble:
+
+ if (lookaheadContext &&
+ ! (LA(1)==ID || LA(1)==LP) ||
+ (LA(1)==ID && Xtest) ||
+ (LA(1)==LP && Ytest) {...
+
+ With the -mrhoist optimization the code would resemble:
+
+ if (lookaheadContext &&
+ (zzpf=0,
+ (LA(1)==ID && (zzpf=1) && Xtest) ||
+ (LA(1)==LP && (zzpf=1) && Ytest) ||
+ !zzpf) {
+
+ These may appear to be of similar complexity at first,
+ but the non-optimized version contains two tests of each
+ context while the optimized version contains only one
+ such test, as well as eliminating some of the inverted
+ logic (" !(...) || ").
+
+ Optimization 4: Computation of predicate gate trees
+
+ When generating code for the gates of predicate expressions
+ antlr 1.33 vanilla uses a recursive procedure to generate
+ "&&" and "||" expressions for testing the lookahead. As each
+ layer of the predicate tree is exposed a new set of "&&" and
+ "||" expressions on the lookahead are generated. In many
+ cases the lookahead being tested has already been tested.
+
+ With -mrhoist a lookahead tree is computed for the entire
+ lookahead expression. This means that predicates with identical
+ context or context which is a subset of another predicate's
+ context disappear.
+
+ This is especially important for predicates formed by rules
+ like the following:
+
+ uppperCaseVowel : <<isUpperCase(LATEXT(1))>>? vowel;
+ vowel: : <<isVowel(LATEXT(1))>>? LETTERS;
+
+ These predicates are combined using AND since both must be
+ satisfied for rule upperCaseVowel. They have identical
+ context which makes this optimization very effective.
+
+ The affect of Items #100a and #100b together can be dramatic. In
+ a very large (but real world) grammar one particular predicate
+ expression was reduced from an (unreadable) 50 predicate leaves,
+ 195 LA(1) terms, and 5500 characters to an (easily comprehensible)
+ 3 predicate leaves (all different) and a *single* LA(1) term.
+
+#99. (Changed in 1.33MR10) Code generation for expression trees
+
+ Expression trees are used for k>1 grammars and predicates with
+ lookahead depth >1. This optimization must be enabled using
+ "-mrhoist on". (Clarification added for 1.33MR11).
+
+ In the processing of expression trees, antlr can generate long chains
+ of token comparisons. Prior to 1.33MR10 there were many redundant
+ parenthesis which caused problems for compilers which could handle
+ expressions of only limited complexity. For example, to test an
+ expression tree (root R A B C D), antlr would generate something
+ resembling:
+
+ (LA(1)==R && (LA(2)==A || (LA(2)==B || (LA(2)==C || LA(2)==D)))))
+
+ If there were twenty tokens to test then there would be twenty
+ parenthesis at the end of the expression.
+
+ In 1.33MR10 the generated code for tree expressions resembles:
+
+ (LA(1)==R && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D))
+
+ For "complex" expressions the output is indented to reflect the LA
+ number being tested:
+
+ (LA(1)==R
+ && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D
+ || LA(2)==E || LA(2)==F)
+ || LA(1)==S
+ && (LA(2)==G || LA(2)==H))
+
+
+ Suggested by S. Bochnak (S.Bochnak@@microTool.com.pl),
+
+#98. (Changed in 1.33MR10) Option "-info p"
+
+ When the user selects option "-info p" the program will generate
+ detailed information about predicates. If the user selects
+ "-mrhoist on" additional detail will be provided explaining
+ the promotion and suppression of predicates. The output is part
+ of the generated file and sandwiched between #if 0/#endif statements.
+
+ Consider the following k=1 grammar:
+
+ start : ( all ) * ;
+
+ all : ( a
+ | b
+ )
+ ;
+
+ a : c B
+ ;
+
+ c : <<LATEXT(1)>>?
+ | B
+ ;
+
+ b : <<LATEXT(1)>>? X
+ ;
+
+ Below is an excerpt of the output for rule "start" for the three
+ predicate options (off, on, and maintenance release style hoisting).
+
+ For those who do not wish to use the "-mrhoist on" option for code
+ generation the option can be used in a "diagnostic" mode to provide
+ valuable information:
+
+ a. where one should insert null actions to inhibit hoisting
+ b. a chain of rule references which shows where predicates are
+ being hoisted
+
+ ======================================================================
+ Example of "-info p" with "-mrhoist on"
+ ======================================================================
+ #if 0
+
+ Hoisting of predicate suppressed by alternative without predicate.
+ The alt without the predicate includes all cases where the
+ predicate is false.
+
+ WITH predicate: line 11 v36.g
+ WITHOUT predicate: line 12 v36.g
+
+ The context set for the predicate:
+
+ B
+
+ The lookahead set for alt WITHOUT the semantic predicate:
+
+ B
+
+ The predicate:
+
+ pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
+
+ set context:
+ B
+ tree context: null
+
+ Chain of referenced rules:
+
+ #0 in rule start (line 1 v36.g) to rule all
+ #1 in rule all (line 3 v36.g) to rule a
+ #2 in rule a (line 8 v36.g) to rule c
+ #3 in rule c (line 11 v36.g)
+
+ #endif
+ &&
+ #if 0
+
+ pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
+
+ set context:
+ X
+ tree context: null
+
+ #endif
+ ======================================================================
+ Example of "-info p" with the default -prc setting ( "-prc off")
+ ======================================================================
+ #if 0
+
+ OR
+ pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
+
+ set context:
+ nil
+ tree context: null
+
+ pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
+
+ set context:
+ nil
+ tree context: null
+
+ #endif
+ ======================================================================
+ Example of "-info p" with "-prc on" and "-mrhoist off"
+ ======================================================================
+ #if 0
+
+ OR
+ pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
+
+ set context:
+ B
+ tree context: null
+
+ pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
+
+ set context:
+ X
+ tree context: null
+
+ #endif
+ ======================================================================
+
+#97. (Fixed in 1.33MR10) "Predicate applied for more than one ... "
+
+ In 1.33 vanilla, the grammar listed below produced this message for
+ the first alternative (only) of rule "b":
+
+ warning: predicate applied for >1 lookahead 1-sequences
+ [you may only want one lookahead 1-sequence to apply.
+ Try using a context guard '(...)? =>'
+
+ In 1.33MR10 the message is issued for both alternatives.
+
+ top : (a)*;
+ a : b | c ;
+
+ b : <<PPP(LATEXT(1))>>? ( AAA | BBB )
+ | <<QQQ(LATEXT(1))>>? ( XXX | YYY )
+ ;
+
+ c : AAA | XXX;
+
+#96. (Fixed in 1.33MR10) Guard predicates ignored when -prc off
+
+ Prior to 1.33MR10, guard predicate code was not generated unless
+ "-prc on" was selected.
+
+ This was incorrect, since "-prc off" (the default) is supposed to
+ disable only AUTOMATIC computation of predicate context, not the
+ programmer specified context supplied by guard predicates.
+
+#95. (Fixed in 1.33MR10) Predicate guard context length was k, not max(k,ck)
+
+ Prior to 1.33MR10, predicate guards were computed to k tokens rather
+ than max(k,ck). Consider the following grammar:
+
+ a : ( A B C)? => <<AAA(LATEXT(1))>>? (A|X) (B|Y) (C|Z) ;
+
+ The code generated by 1.33 vanilla with "-k 1 -ck 3 -prc on"
+ for the predicate in "a" resembles:
+
+ if ( (! LA(1)==A) || AAA(LATEXT(1))) {...
+
+ With 1.33MR10 and the same options the code resembles:
+
+ if ( (! (LA(1)==A && LA(2)==B && LA(3)==C) || AAA(LATEXT(1))) {...
+
+#94. (Fixed in 1.33MR10) Predicates followed by rule references
+
+ Prior to 1.33MR10, a semantic predicate which referenced a token
+ which was off the end of the rule caused an incomplete context
+ to be computed (with "-prc on") for the predicate under some circum-
+ stances. In some cases this manifested itself as illegal C code
+ (e.g. "LA(2)==[Ep](1)" in the k=2 examples below:
+
+ all : ( a ) *;
+
+ a : <<AAA(LATEXT(2))>>? ID X
+ | <<BBB(LATEXT(2))>>? Y
+ | Z
+ ;
+
+ This might also occur when the semantic predicate was followed
+ by a rule reference which was shorter than the length of the
+ semantic predicate:
+
+ all : ( a ) *;
+
+ a : <<AAA(LATEXT(2))>>? ID X
+ | <<BBB(LATEXT(2))>>? y
+ | Z
+ ;
+
+ y : Y ;
+
+ Depending on circumstance, the resulting context might be too
+ generous because it was too short, or too restrictive because
+ of missing alternatives.
+
+#93. (Changed in 1.33MR10) Definition of Purify macro
+
+ Ofer Ben-Ami (gremlin@cs.huji.ac.il) has supplied a definition
+ for the Purify macro:
+
+ #define PURIFY(r, s) memset((char *) &(r), '\0', (s));
+
+ Note: This may not be the right thing to do for C++ objects that
+ have constructors. Reported by Bonny Rais (bonny@werple.net.au).
+
+ For those cases one should #define PURIFY to an empty macro in the
+ #header or #first actions.
+
+#92. (Fixed in 1.33MR10) Guarded predicates and hoisting
+
+ When a guarded predicate participates in hoisting it is linked into
+ a predicate expression tree. Prior to 1.33MR10 this link was never
+ cleared and the next time the guard was used to construct a new
+ tree the link could contain a spurious reference to another element
+ which had previosly been joined to it in the semantic predicate tree.
+
+ For example:
+
+ start : ( all ) *;
+ all : ( a | b ) ;
+
+ start2 : ( all2 ) *;
+ all2 : ( a ) ;
+
+ a : (A)? => <<AAA(LATEXT(1))>>? A ;
+ b : (B)? => <<BBB(LATEXT(1))>>? B ;
+
+ Prior to 1.33MR10 the code for "start2" would include a spurious
+ reference to the BBB predicate which was left from constructing
+ the predicate tree for rule "start" (i.e. or(AAA,BBB) ).
+
+ In 1.33MR10 this problem is avoided by cloning the original guard
+ each time it is linked into a predicate tree.
+
+#91. (Changed in 1.33MR10) Extensive changes to semantic pred hoisting
+
+ ============================================
+ This has been rendered obsolete by Item #117
+ ============================================
+
+#90. (Fixed in 1.33MR10) Semantic pred with LT(i) and i>max(k,ck)
+
+ There is a bug in antlr 1.33 vanilla and all maintenance releases
+ prior to 1.33MR10 which allows semantic predicates to reference
+ an LT(i) or LATEXT(i) where i is larger than max(k,ck). When
+ this occurs antlr will attempt to mark the ith element of an array
+ in which there are only max(k,ck) elements. The result cannot
+ be predicted.
+
+ Using LT(i) or LATEXT(i) for i>max(k,ck) is reported as an error
+ in 1.33MR10.
+
+#89. Rescinded
+
+#88. (Fixed in 1.33MR10) Tokens used in semantic predicates in guess mode
+
+ Consider the behavior of a semantic predicate during guess mode:
+
+ rule : a:A (
+ <<test($a)>>? b:B
+ | c:C
+ );
+
+ Prior to MR10 the assignment of the token or attribute to
+ $a did not occur during guess mode, which would cause the
+ semantic predicate to misbehave because $a would be null.
+
+ In 1.33MR10 a semantic predicate with a reference to an
+ element label (such as $a) forces the assignment to take
+ place even in guess mode.
+
+ In order to work, this fix REQUIRES use of the $label format
+ for token pointers and attributes referenced in semantic
+ predicates.
+
+ The fix does not apply to semantic predicates using the
+ numeric form to refer to attributes (e.g. <<test($1)>>?).
+ The user will receive a warning for this case.
+
+ Reported by Rob Trout (trout@mcs.cs.kent.edu).
+
+#87. (Fixed in 1.33MR10) Malformed guard predicates
+
+ Context guard predicates may contain only references to
+ tokens. They may not contain references to (...)+ and
+ (...)* blocks. This is now checked. This replaces the
+ fatal error message in item #78 with an appropriate
+ (non-fatal) error messge.
+
+ In theory, context guards should be allowed to reference
+ rules. However, I have not had time to fix this.
+ Evaluation of the guard takes place before all rules have
+ been read, making it difficult to resolve a forward reference
+ to rule "zzz" - it hasn't been read yet ! To postpone evaluation
+ of the guard until all rules have been read is too much
+ for the moment.
+
+#86. (Fixed in 1.33MR10) Unequal set size in set_sub
+
+ Routine set_sub() in pccts/support/set/set.h did not work
+ correctly when the sets were of unequal sizes. Rewrote
+ set_equ to make it simpler and remove unnecessary and
+ expensive calls to set_deg(). This routine was not used
+ in 1.33 vanila.
+
+#85. (Changed in 1.33MR10) Allow redefinition of MaxNumFiles
+
+ Raised the maximum number of input files to 99 from 20.
+ Put a #ifndef/#endif around the "#define MaxNumFiles 99".
+
+#84. (Fixed in 1.33MR10) Initialize zzBadTok in macro zzRULE
+
+ Initialize zzBadTok to NULL in zzRULE macro of AParser.h.
+ in order to get rid of warning messages.
+
+#83. (Fixed in 1.33MR10) False warnings with -w2 for #tokclass
+
+ When -w2 is selected antlr gives inappropriate warnings about
+ #tokclass names not having any associated regular expressions.
+ Since a #tokclass is not a "real" token it will never have an
+ associated regular expression and there should be no warning.
+
+ Reported by Derek Pappas (derek.pappas@eng.sun.com)
+
+#82. (Fixed in 1.33MR10) Computation of follow sets with multiple cycles
+
+ Reinier van den Born (reinier@vnet.ibm.com) reported a problem
+ in the computation of follow sets by antlr. The problem (bug)
+ exists in 1.33 vanilla and all maintenance releases prior to 1.33MR10.
+
+ The problem involves the computation of follow sets when there are
+ cycles - rules which have mutual references. I believe the problem
+ is restricted to cases where there is more than one cycle AND
+ elements of those cycles have rules in common. Even when this
+ occurs it may not affect the code generated - but it might. It
+ might also lead to undetected ambiguities.
+
+ There were no changes in antlr or dlg output from the revised version.
+
+ The following fragment demonstates the problem by giving different
+ follow sets (option -pa) for var_access when built with k=1 and ck=2 on
+ 1.33 vanilla and 1.33MR10:
+
+ echo_statement : ECHO ( echo_expr )*
+ ;
+
+ echo_expr : ( command )?
+ | expression
+ ;
+
+ command : IDENTIFIER
+ { concat }
+ ;
+
+ expression : operand ( OPERATOR operand )*
+ ;
+
+ operand : value
+ | START command END
+ ;
+
+ value : concat
+ | TYPE operand
+ ;
+
+ concat : var_access { CONCAT value }
+ ;
+
+ var_access : IDENTIFIER { INDEX }
+
+ ;
+#81. (Changed in 1.33MR10) C mode use of attributes and ASTs
+
+ Reported by Isaac Clark (irclark@mindspring.com).
+
+ C mode code ignores attributes returned by rules which are
+ referenced using element labels when ASTs are enabled (-gt option).
+
+ 1. start : r:rule t:Token <<$start=$r;>>
+
+ The $r refrence will not work when combined with
+ the -gt option.
+
+ 2. start : t:Token <<$start=$t;>>
+
+ The $t reference works in all cases.
+
+ 3. start : rule <<$0=$1;>>
+
+ Numeric labels work in all cases.
+
+ With MR10 the user will receive an error message for case 1 when
+ the -gt option is used.
+
+#80. (Fixed in 1.33MR10) (...)? as last alternative of block
+
+ A construct like the following:
+
+ rule : a
+ | (b)?
+ ;
+
+ does not make sense because there is no alternative when
+ the guess block fails. This is now reported as a warning
+ to the user.
+
+ Previously, there was a code generation error for this case:
+ the guess block was not "closed" when the guess failed.
+ This could cause an infinite loop or other problems. This
+ is now fixed.
+
+ Example problem:
+
+ #header<<
+ #include <stdio.h>
+ #include "charptr.h"
+ >>
+
+ <<
+ #include "charptr.c"
+ main ()
+ {
+ ANTLR(start(),stdin);
+ }
+ >>
+
+ #token "[\ \t]+" << zzskip(); >>
+ #token "[\n]" << zzline++; zzskip(); >>
+
+ #token Word "[a-z]+"
+ #token Number "[0-9]+"
+
+
+ start : (test1)?
+ | (test2)?
+ ;
+ test1 : (Word Word Word Word)?
+ | (Word Word Word Number)?
+ ;
+ test2 : (Word Word Number Word)?
+ | (Word Word Number Number)?
+ ;
+
+ Test data which caused infinite loop:
+
+ a 1 a a
+
+#79. (Changed in 1.33MR10) Use of -fh with multiple parsers
+
+ Previously, antlr always used the pre-processor symbol
+ STDPCCTS_H as a gate for the file stdpccts.h. This
+ caused problems when there were multiple parsers defined
+ because they used the same gate symbol.
+
+ In 1.33MR10, the -fh filename is used to generate the
+ gate file for stdpccts.h. For instance:
+
+ antlr -fh std_parser1.h
+
+ generates the pre-processor symbol "STDPCCTS_std_parser1_H".
+
+ Reported by Ramanathan Santhanam (ps@kumaran.com).
+
+#78. (Changed in 1.33MR9) Guard predicates that refer to rules
+
+ ------------------------
+ Please refer to Item #87
+ ------------------------
+
+ Guard predicates are processed during an early phase
+ of antlr (during parsing) before all data structures
+ are completed.
+
+ There is an apparent bug in earlier versions of 1.33
+ which caused guard predicates which contained references
+ to rules (rather than tokens) to reference a structure
+ which hadn't yet been initialized.
+
+ In some cases (perhaps all cases) references to rules
+ in guard predicates resulted in the use of "garbage".
+
+#79. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
+
+ Previously, the maximum length file name was set
+ arbitrarily to 300 characters in antlr, dlg, and sorcerer.
+
+ The config.h file now attempts to define the maximum length
+ filename using _MAX_PATH from stdlib.h before falling back
+ to using the value 300.
+
+#78. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
+
+ Put #ifndef/#endif around definition of ZZLEXBUFSIZE in
+ antlr.
+
+#77. (Changed in 1.33MR9) Arithmetic overflow for very large grammars
+
+ In routine HandleAmbiguities() antlr attempts to compute the
+ number of possible elements in a set that is order of
+ number-of-tokens raised to the number-of-lookahead-tokens power.
+ For large grammars or large lookahead (e.g. -ck 7) this can
+ cause arithmetic overflow.
+
+ With 1.33MR9, arithmetic overflow in this computation is reported
+ the first time it happens. The program continues to run and
+ the program branches based on the assumption that the computed
+ value is larger than any number computed by counting actual cases
+ because 2**31 is larger than the number of bits in most computers.
+
+ Before 1.33MR9 overflow was not reported. The behavior following
+ overflow is not predictable by anyone but the original author.
+
+ NOTE
+
+ In 1.33MR10 the warning message is suppressed.
+ The code which detects the overflow allows the
+ computation to continue without an error. The
+ error message itself made made users worry.
+
+#76. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
+
+ Jeff Vincent has convinced me to make ANTLRCommonToken and
+ ANTLRCommonNoRefCountToken use variable length strings
+ allocated from the heap rather than fixed length strings.
+ By suitable definition of setText(), the copy constructor,
+ and operator =() it is possible to maintain "copy" semantics.
+ By "copy" semantics I mean that when a token is copied from
+ an existing token it receives its own, distinct, copy of the
+ text allocated from the heap rather than simply a pointer
+ to the original token's text.
+
+ ============================================================
+ W * A * R * N * I * N * G
+ ============================================================
+
+ It is possible that this may cause problems for some users.
+ For those users I have included the old version of AToken.h as
+ pccts/h/AToken_traditional.h.
+
+#75. (Changed in 1.33MR9) Bruce Guenter (bruceg@qcc.sk.ca)
+
+ Make DLGStringInput const correct. Since this is infrequently
+ subclassed, it should affect few users, I hope.
+
+#74. (Changed in 1.33MR9) -o (output directory) option
+
+ Antlr does not properly handle the -o output directory option
+ when the filename of the grammar contains a directory part. For
+ example:
+
+ antlr -o outdir pccts_src/myfile.g
+
+ causes antlr create a file called "outdir/pccts_src/myfile.cpp.
+ It SHOULD create outdir/myfile.cpp
+
+ The suggested code fix has been installed in antlr, dlg, and
+ Sorcerer.
+
+#73. (Changed in 1.33MR9) Hoisting of semantic predicates and -mrhoist
+
+ ============================================
+ This has been rendered obsolete by Item #117
+ ============================================
+
+#72. (Changed in 1.33MR9) virtual saveState()/restoreState()/guess_XXX
+
+ The following methods in ANTLRParser were made virtual at
+ the request of S. Bochnak (S.Bochnak@microTool.com.pl):
+
+ saveState() and restoreState()
+ guess(), guess_fail(), and guess_done()
+
+#71. (Changed in 1.33MR9) Access to omitted command line argument
+
+ If a switch requiring arguments is the last thing on the
+ command line, and the argument is omitted, antlr would core.
+
+ antlr test.g -prc
+
+ instead of
+
+ antlr test.g -prc off
+
+#70. (Changed in 1.33MR9) Addition of MSVC .dsp and .mak build files
+
+ The following MSVC .dsp and .mak files for pccts and sorcerer
+ were contributed by Stanislaw Bochnak (S.Bochnak@microTool.com.pl)
+ and Jeff Vincent (JVincent@novell.com)
+
+ PCCTS Distribution Kit
+ ----------------------
+ pccts/PCCTSMSVC50.dsw
+
+ pccts/antlr/AntlrMSVC50.dsp
+ pccts/antlr/AntlrMSVC50.mak
+
+ pccts/dlg/DlgMSVC50.dsp
+ pccts/dlg/DlgMSVC50.mak
+
+ pccts/support/msvc.dsp
+
+ Sorcerer Distribution Kit
+ -------------------------
+ pccts/sorcerer/SorcererMSVC50.dsp
+ pccts/sorcerer/SorcererMSVC50.mak
+
+ pccts/sorcerer/lib/msvc.dsp
+
+#69. (Changed in 1.33MR9) Change "unsigned int" to plain "int"
+
+ Declaration of max_token_num in misc.c as "unsigned int"
+ caused comparison between signed and unsigned ints giving
+ warning message without any special benefit.
+
+#68. (Changed in 1.33MR9) Add void return for dlg internal_error()
+
+ Get rid of "no return value" message in internal_error()
+ in file dlg/support.c and dlg/dlg.h.
+
+#67. (Changed in Sor) sor.g: lisp() has no return value
+
+ Added a "void" for the return type.
+
+#66. (Added to Sor) sor.g: ZZLEXBUFSIZE enclosed in #ifndef/#endif
+
+ A user needed to be able to change the ZZLEXBUFSIZE for
+ sor. Put the definition of ZZLEXBUFSIZE inside #ifndef/#endif
+
+#65. (Changed in 1.33MR9) PCCTSAST::deepCopy() and ast_dup() bug
+
+ Jeff Vincent (JVincent@novell.com) found that deepCopy()
+ made new copies of only the direct descendents. No new
+ copies were made of sibling nodes, Sibling pointers are
+ set to zero by shallowCopy().
+
+ PCCTS_AST::deepCopy() has been changed to make a
+ deep copy in the traditional sense.
+
+ The deepCopy() routine depends on the behavior of
+ shallowCopy(). In all sor examples I've found,
+ shallowCopy() zeroes the right and down pointers.
+
+ Original Tree Original deepCopy() Revised deepCopy
+ ------------- ------------------- ----------------
+ a->b->c A A
+ | | |
+ d->e->f D D->E->F
+ | | |
+ g->h->i G G->H->I
+ | |
+ j->k J->K
+
+ While comparing deepCopy() for C++ mode with ast_dup for
+ C mode I found a problem with ast_dup().
+
+ Routine ast_dup() has been changed to make a deep copy
+ in the traditional sense.
+
+ Original Tree Original ast_dup() Revised ast_dup()
+ ------------- ------------------- ----------------
+ a->b->c A->B->C A
+ | | |
+ d->e->f D->E->F D->E->F
+ | | |
+ g->h->i G->H->I G->H->I
+ | | |
+ j->k J->K J->K
+
+
+ I believe this affects transform mode sorcerer programs only.
+
+#64. (Changed in 1.33MR9) anltr/hash.h prototype for killHashTable()
+
+#63. (Changed in 1.33MR8) h/charptr.h does not zero pointer after free
+
+ The charptr.h routine now zeroes the pointer after free().
+
+ Reported by Jens Tingleff (jensting@imaginet.fr)
+
+#62. (Changed in 1.33MR8) ANTLRParser::resynch had static variable
+
+ The static variable "consumed" in ANTLRParser::resynch was
+ changed into an instance variable of the class with the
+ name "resynchConsumed".
+
+ Reported by S.Bochnak@microTool.com.pl
+
+#61. (Changed in 1.33MR8) Using rule>[i,j] when rule has no return values
+
+ Previously, the following code would cause antlr to core when
+ it tried to generate code for rule1 because rule2 had no return
+ values ("upward inheritance"):
+
+ rule1 : <<int i; int j>>
+ rule2 > [i,j]
+ ;
+
+ rule2 : Anything ;
+
+ Reported by S.Bochnak@microTool.com.pl
+
+ Verified correct operation of antlr MR8 when missing or extra
+ inheritance arguments for all combinations. When there are
+ missing or extra arguments code will still be generated even
+ though this might cause the invocation of a subroutine with
+ the wrong number of arguments.
+
+#60. (Changed in 1.33MR7) Major changes to exception handling
+
+ There were significant problems in the handling of exceptions
+ in 1.33 vanilla. The general problem is that it can only
+ process one level of exception handler. For example, a named
+ exception handler, an exception handler for an alternative, or
+ an exception for a subrule always went to the rule's exception
+ handler if there was no "catch" which matched the exception.
+
+ In 1.33MR7 the exception handlers properly "nest". If an
+ exception handler does not have a matching "catch" then the
+ nextmost outer exception handler is checked for an appropriate
+ "catch" clause, and so on until an exception handler with an
+ appropriate "catch" is found.
+
+ There are still undesirable features in the way exception
+ handlers are implemented, but I do not have time to fix them
+ at the moment:
+
+ The exception handlers for alternatives are outside the
+ block containing the alternative. This makes it impossible
+ to access variables declared in a block or to resume the
+ parse by "falling through". The parse can still be easily
+ resumed in other ways, but not in the most natural fashion.
+
+ This results in an inconsistentcy between named exception
+ handlers and exception handlers for alternatives. When
+ an exception handler for an alternative "falls through"
+ it goes to the nextmost outer handler - not the "normal
+ action".
+
+ A major difference between 1.33MR7 and 1.33 vanilla is
+ the default action after an exception is caught:
+
+ 1.33 Vanilla
+ ------------
+ In 1.33 vanilla the signal value is set to zero ("NoSignal")
+ and the code drops through to the code following the exception.
+ For named exception handlers this is the "normal action".
+ For alternative exception handlers this is the rule's handler.
+
+ 1.33MR7
+ -------
+ In 1.33MR7 the signal value is NOT automatically set to zero.
+
+ There are two cases:
+
+ For named exception handlers: if the signal value has been
+ set to zero the code drops through to the "normal action".
+
+ For all other cases the code branches to the nextmost outer
+ exception handler until it reaches the handler for the rule.
+
+ The following macros have been defined for convenience:
+
+ C/C++ Mode Name
+ --------------------
+ (zz)suppressSignal
+ set signal & return signal arg to 0 ("NoSignal")
+ (zz)setSignal(intValue)
+ set signal & return signal arg to some value
+ (zz)exportSignal
+ copy the signal value to the return signal arg
+
+ I'm not sure why PCCTS make a distinction between the local
+ signal value and the return signal argument, but I'm loathe
+ to change the code. The burden of copying the local signal
+ value to the return signal argument can be given to the
+ default signal handler, I suppose.
+
+#59. (Changed in 1.33MR7) Prototypes for some functions
+
+ Added prototypes for the following functions to antlr.h
+
+ zzconsumeUntil()
+ zzconsumeUntilToken()
+
+#58. (Changed in 1.33MR7) Added defintion of zzbufsize to dlgauto.h
+
+#57. (Changed in 1.33MR7) Format of #line directive
+
+ Previously, the -gl directive for line 1234 would
+ resemble: "# 1234 filename.g". This caused problems
+ for some compilers/pre-processors. In MR7 it generates
+ "#line 1234 filename.g".
+
+#56. (Added in 1.33MR7) Jan Mikkelsen <janm@zeta.org.au>
+
+ Move PURIFY macro invocaton to after rule's init action.
+
+#55. (Fixed in 1.33MR7) Unitialized variables in ANTLRParser
+
+ Member variables inf_labase and inf_last were not initialized.
+ (See item #50.)
+
+#54. (Fixed in 1.33MR6) Brad Schick (schick@interacess.com)
+
+ Previously, the following constructs generated the same
+ code:
+
+ rule1 : (A B C)?
+ | something-else
+ ;
+
+ rule2 : (A B C)? ()
+ | something-else
+ ;
+
+ In all versions of pccts rule1 guesses (A B C) and then
+ consume all three tokens if the guess succeeds. In MR6
+ rule2 guesses (A B C) but consumes NONE of the tokens
+ when the guess succeeds because "()" matches epsilon.
+
+#53. (Explanation for 1.33MR6) What happens after an exception is caught ?
+
+ The Book is silent about what happens after an exception
+ is caught.
+
+ The following code fragment prints "Error Action" followed
+ by "Normal Action".
+
+ test : Word ex:Number <<printf("Normal Action\n");>>
+ exception[ex]
+ catch NoViableAlt:
+ <<printf("Error Action\n");>>
+ ;
+
+ The reason for "Normal Action" is that the normal flow of the
+ program after a user-written exception handler is to "drop through".
+ In the case of an exception handler for a rule this results in
+ the exection of a "return" statement. In the case of an
+ exception handler attached to an alternative, rule, or token
+ this is the code that would have executed had there been no
+ exception.
+
+ The user can achieve the desired result by using a "return"
+ statement.
+
+ test : Word ex:Number <<printf("Normal Action\n");>>
+ exception[ex]
+ catch NoViableAlt:
+ <<printf("Error Action\n"); return;>>
+ ;
+
+ The most powerful mechanism for recovery from parse errors
+ in pccts is syntactic predicates because they provide
+ backtracking. Exceptions allow "return", "break",
+ "consumeUntil(...)", "goto _handler", "goto _fail", and
+ changing the _signal value.
+
+#52. (Fixed in 1.33MR6) Exceptions without syntactic predicates
+
+ The following generates bad code in 1.33 if no syntactic
+ predicates are present in the grammar.
+
+ test : Word ex:Number <<printf("Normal Action\n");>>
+ exception[ex]
+ catch NoViableAlt:
+ <<printf("Error Action\n");>>
+
+ There is a reference to a guess variable. In C mode
+ this causes a compiler error. In C++ mode it generates
+ an extraneous check on member "guessing".
+
+ In MR6 correct code is generated for both C and C++ mode.
+
+#51. (Added to 1.33MR6) Exception operator "@" used without exceptions
+
+ In MR6 added a warning when the exception operator "@" is
+ used and no exception group is defined. This is probably
+ a case where "\@" or "@" is meant.
+
+#50. (Fixed in 1.33MR6) Gunnar Rxnning (gunnar@candleweb.no)
+ http://www.candleweb.no/~gunnar/
+
+ Routines zzsave_antlr_state and zzrestore_antlr_state don't
+ save and restore all the data needed when switching states.
+
+ Suggested patch applied to antlr.h and err.h for MR6.
+
+#49. (Fixed in 1.33MR6) Sinan Karasu (sinan@boeing.com)
+
+ Generated code failed to turn off guess mode when leaving a
+ (...)+ block which contained a guess block. The result was
+ an infinite loop. For example:
+
+ rule : (
+ (x)?
+ | y
+ )+
+
+ Suggested code fix implemented in MR6. Replaced
+
+ ... else if (zzcnt>1) break;
+
+ with:
+
+ C++ mode:
+ ... else if (zzcnt>1) {if (!zzrv) zzGUESS_DONE; break;};
+ C mode:
+ ... else if (zzcnt>1) {if (zzguessing) zzGUESS_DONE; break;};
+
+#48. (Fixed in 1.33MR6) Invalid exception element causes core
+
+ A label attached to an invalid construct can cause
+ pccts to crash while processing the exception associated
+ with the label. For example:
+
+ rule : t:(B C)
+ exception[t] catch MismatchedToken: <<printf(...);>>
+
+ Version MR6 generates the message:
+
+ reference in exception handler to undefined label 't'
+
+#47. (Fixed in 1.33MR6) Manuel Ornato
+
+ Under some circumstances involving a k >1 or ck >1
+ grammar and a loop block (i.e. (...)* ) pccts will
+ fail to detect a syntax error and loop indefinitely.
+ The problem did not exist in 1.20, but has existed
+ from 1.23 to the present.
+
+ Fixed in MR6.
+
+ ---------------------------------------------------
+ Complete test program
+ ---------------------------------------------------
+ #header<<
+ #include <stdio.h>
+ #include "charptr.h"
+ >>
+
+ <<
+ #include "charptr.c"
+ main ()
+ {
+ ANTLR(global(),stdin);
+ }
+ >>
+
+ #token "[\ \t]+" << zzskip(); >>
+ #token "[\n]" << zzline++; zzskip(); >>
+
+ #token B "b"
+ #token C "c"
+ #token D "d"
+ #token E "e"
+ #token LP "\("
+ #token RP "\)"
+
+ #token ANTLREOF "@"
+
+ global : (
+ (E liste)
+ | liste
+ | listed
+ ) ANTLREOF
+ ;
+
+ listeb : LP ( B ( B | C )* ) RP ;
+ listec : LP ( C ( B | C )* ) RP ;
+ listed : LP ( D ( B | C )* ) RP ;
+ liste : ( listeb | listec )* ;
+
+ ---------------------------------------------------
+ Sample data causing infinite loop
+ ---------------------------------------------------
+ e (d c)
+ ---------------------------------------------------
+
+#46. (Fixed in 1.33MR6) Robert Richter
+ (Robert.Richter@infotech.tu-chemnitz.de)
+
+ This item from the list of known problems was
+ fixed by item #18 (below).
+
+#45. (Fixed in 1.33MR6) Brad Schick (schick@interaccess.com)
+
+ The dependency scanner in VC++ mistakenly sees a
+ reference to an MPW #include file even though properly
+ #ifdef/#endif in config.h. The suggested workaround
+ has been implemented:
+
+ #ifdef MPW
+ .....
+ #define MPW_CursorCtl_Header <CursorCtl.h>
+ #include MPW_CursorCtl_Header
+ .....
+ #endif
+
+#44. (Fixed in 1.33MR6) cast malloc() to (char *) in charptr.c
+
+ Added (char *) cast for systems where malloc returns "void *".
+
+#43. (Added to 1.33MR6) Bruce Guenter (bruceg@qcc.sk.ca)
+
+ Add setLeft() and setUp methods to ASTDoublyLinkedBase
+ for symmetry with setRight() and setDown() methods.
+
+#42. (Fixed in 1.33MR6) Jeff Katcher (jkatcher@nortel.ca)
+
+ C++ style comment in antlr.c corrected.
+
+#41. (Added in 1.33MR6) antlr -stdout
+
+ Using "antlr -stdout ..." forces the text that would
+ normally go to the grammar.c or grammar.cpp file to
+ stdout.
+
+#40. (Added in 1.33MR6) antlr -tab to change tab stops
+
+ Using "antlr -tab number ..." changes the tab stops
+ for the grammar.c or grammar.cpp file. The number
+ must be between 0 and 8. Using 0 gives tab characters,
+ values between 1 and 8 give the appropriate number of
+ space characters.
+
+#39. (Fixed in 1.33MR5) Jan Mikkelsen <janm@zeta.org.au>
+
+ Commas in function prototype still not correct under
+ some circumstances. Suggested code fix installed.
+
+#38. (Fixed in 1.33MR5) ANTLRTokenBuffer constructor
+
+ Have ANTLRTokenBuffer ctor initialize member "parser" to null.
+
+#37. (Fixed in 1.33MR4) Bruce Guenter (bruceg@qcc.sk.ca)
+
+ In ANTLRParser::FAIL(int k,...) released memory pointed to by
+ f[i] (as well as f itself. Should only free f itself.
+
+#36. (Fixed in 1.33MR3) Cortland D. Starrett (cort@shay.ecn.purdue.edu)
+
+ Neglected to properly declare isDLGmaxToken() when fixing problem
+ reported by Andreas Magnusson.
+
+ Undo "_retv=NULL;" change which caused problems for return values
+ from rules whose return values weren't pointers.
+
+ Failed to create bin directory if it didn't exist.
+
+#35. (Fixed in 1.33MR2) Andreas Magnusson
+(Andreas.Magnusson@mailbox.swipnet.se)
+
+ Repair bug introduced by 1.33MR1 for #tokdefs. The original fix
+ placed "DLGmaxToken=9999" and "DLGminToken=0" in the TokenType enum
+ in order to fix a problem with an aggresive compiler assigning an 8
+ bit enum which might be too narrow. This caused #tokdefs to assume
+ that there were 9999 real tokens. The repair to the fix causes antlr to
+ ignore TokenTypes "DLGmaxToken" and "DLGminToken" in a #tokdefs file.
+
+#34. (Added to 1.33MR1) Add public DLGLexerBase::set_line(int newValue)
+
+ Previously there was no public function for changing the line
+ number maintained by the lexer.
+
+#33. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)
+
+ Accidental use of EXIT_FAILURE rather than PCCTS_EXIT_FAILURE
+ in pccts/h/AParser.cpp.
+
+#32. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)
+
+ In PCCTSAST.cpp lines 405 and 466: Change
+
+ free (t)
+ to
+ free ( (char *)t );
+
+ to match prototype.
+
+#31. (Added to 1.33MR1) Pointer to parser in ANTLRTokenBuffer
+ Pointer to parser in DLGLexerBase
+
+ The ANTLRTokenBuffer class now contains a pointer to the
+ parser which is using it. This is established by the
+ ANTLRParser constructor calling ANTLRTokenBuffer::
+ setParser(ANTLRParser *p).
+
+ When ANTLRTokenBuffer::setParser(ANTLRParser *p) is
+ called it saves the pointer to the parser and then
+ calls ANTLRTokenStream::setParser(ANTLRParser *p)
+ so that the lexer can also save a pointer to the
+ parser.
+
+ There is also a function getParser() in each class
+ with the obvious purpose.
+
+ It is possible that these functions will return NULL
+ under some circumstances (e.g. a non-DLG lexer is used).
+
+#30. (Added to 1.33MR1) function tokenName(int token) standard
+
+ The generated parser class now includes the
+ function:
+
+ static const ANTLRChar * tokenName(int token)
+
+ which returns a pointer to the "name" corresponding
+ to the token.
+
+ The base class (ANTLRParser) always includes the
+ member function:
+
+ const ANTLRChar * parserTokenName(int token)
+
+ which can be accessed by objects which have a pointer
+ to an ANTLRParser, but do not know the name of the
+ parser class (e.g. ANTLRTokenBuffer and DLGLexerBase).
+
+#29. (Added to 1.33MR1) Debugging DLG lexers
+
+ If the pre-processor symbol DEBUG_LEXER is defined
+ then DLexerBase will include code for printing out
+ key information about tokens which are recognized.
+
+ The debug feature of the lexer is controlled by:
+
+ int previousDebugValue=lexer.debugLexer(newValue);
+
+ a value of 0 disables output
+ a value of 1 enables output
+
+ Even if the lexer debug code is compiled into DLexerBase
+ it must be enabled before any output is generated. For
+ example:
+
+ DLGFileInput in(stdin);
+ MyDLG lexer(&in,2000);
+
+ lexer.setToken(&aToken);
+
+ #if DEBUG_LEXER
+ lexer.debugLexer(1); // enable debug information
+ #endif
+
+#28. (Added to 1.33MR1) More control over DLG header
+
+ Version 1.33MR1 adds the following directives to PCCTS
+ for C++ mode:
+
+ #lexprefix <<source code>>
+
+ Adds source code to the DLGLexer.h file
+ after the #include "DLexerBase.h" but
+ before the start of the class definition.
+
+ #lexmember <<source code>>
+
+ Adds source code to the DLGLexer.h file
+ as part of the DLGLexer class body. It
+ appears immediately after the start of
+ the class and a "public: statement.
+
+#27. (Fixed in 1.33MR1) Comments in DLG actions
+
+ Previously, DLG would not recognize comments as a special case.
+ Thus, ">>" in the comments would cause errors. This is fixed.
+
+#26. (Fixed in 1.33MR1) Removed static variables from error routines
+
+ Previously, the existence of statically allocated variables
+ in some of the parser's member functions posed a danger when
+ there was more than one parser active.
+
+ Replaced with dynamically allocated/freed variables in 1.33MR1.
+
+#25. (Fixed in 1.33MR1) Use of string literals in semantic predicates
+
+ Previously, it was not possible to place a string literal in
+ a semantic predicate because it was not properly "stringized"
+ for the report of a failed predicate.
+
+#24. (Fixed in 1.33MR1) Continuation lines for semantic predicates
+
+ Previously, it was not possible to continue semantic
+ predicates across a line because it was not properly
+ "stringized" for the report of a failed predicate.
+
+ rule : <<ifXYZ()>>?[ a very
+ long statement ]
+
+#23. (Fixed in 1.33MR1) {...} envelope for failed semantic predicates
+
+ Previously, there was a code generation error for failed
+ semantic predicates:
+
+ rule : <<xyz()>>?[ stmt1; stmt2; ]
+
+ which generated code which resembled:
+
+ if (! xyz()) stmt1; stmt2;
+
+ It now puts the statements in a {...} envelope:
+
+ if (! xyz()) { stmt1; stmt2; };
+
+#22. (Fixed in 1.33MR1) Continuation of #token across lines using "\"
+
+ Previously, it was not possible to continue a #token regular
+ expression across a line. The trailing "\" and newline caused
+ a newline to be inserted into the regular expression by DLG.
+
+ Fixed in 1.33MR1.
+
+#21. (Fixed in 1.33MR1) Use of ">>" (right shift operator in DLG actions
+
+ It is now possible to use the C++ right shift operator ">>"
+ in DLG actions by using the normal escapes:
+
+ #token "shift-right" << value=value \>\> 1;>>
+
+#20. (Version 1.33/19-Jan-97 Karl Eccleson <karle@microrobotics.co.uk>
+ P.A. Keller (P.A.Keller@bath.ac.uk)
+
+ There is a problem due to using exceptions with the -gh option.
+
+ Suggested fix now in 1.33MR1.
+
+#19. (Fixed in 1.33MR1) Tom Piscotti and John Lilley
+
+ There were problems suppressing messages to stdin and stdout
+ when running in a window environment because some functions
+ which uses fprint were not virtual.
+
+ Suggested change now in 1.33MR1.
+
+ I believe all functions containing error messages (excluding those
+ indicating internal inconsistency) have been placed in functions
+ which are virtual.
+
+#18. (Version 1.33/ 22-Nov-96) John Bair (jbair@iftime.com)
+
+ Under some combination of options a required "return _retv" is
+ not generated.
+
+ Suggested fix now in 1.33MR1.
+
+#17. (Version 1.33/3-Sep-96) Ron House (house@helios.usq.edu.au)
+
+ The routine ASTBase::predorder_action omits two "tree->"
+ prefixes, which results in the preorder_action belonging
+ to the wrong node to be invoked.
+
+ Suggested fix now in 1.33MR1.
+
+#16. (Version 1.33/7-Jun-96) Eli Sternheim <eli@interhdl.com>
+
+ Routine consumeUntilToken() does not check for end-of-file
+ condition.
+
+ Suggested fix now in 1.33MR1.
+
+#15. (Version 1.33/8 Apr 96) Asgeir Olafsson <olafsson@cstar.ac.com>
+
+ Problem with tree duplication of doubly linked ASTs in ASTBase.cpp.
+
+ Suggested fix now in 1.33MR1.
+
+#14. (Version 1.33/28-Feb-96) Andreas.Magnusson@mailbox.swipnet.se
+
+ Problem with definition of operator = (const ANTLRTokenPtr rhs).
+
+ Suggested fix now in 1.33MR1.
+
+#13. (Version 1.33/13-Feb-96) Franklin Chen (chen@adi.com)
+
+ Sun C++ Compiler 3.0.1 can't compile testcpp/1 due to goto in
+ block with destructors.
+
+ Apparently fixed. Can't locate "goto".
+
+#12. (Version 1.33/10-Nov-95) Minor problems with 1.33 code
+
+ The following items have been fixed in 1.33MR1:
+
+ 1. pccts/antlr/main.c line 142
+
+ "void" appears in classic C code
+
+ 2. no makefile in support/genmk
+
+ 3. EXIT_FAILURE/_SUCCESS instead of PCCTS_EXIT_FAILURE/_SUCCESS
+
+ pccts/h/PCCTSAST.cpp
+ pccts/h/DLexerBase.cpp
+ pccts/testcpp/6/test.g
+
+ 4. use of "signed int" isn't accepted by AT&T cfront
+
+ pccts/h/PCCTSAST.h line 42
+
+ 5. in call to ANTLRParser::FAIL the var arg err_k is passed as
+ "int" but is declared "unsigned int".
+
+ 6. I believe that a failed validation predicate still does not
+ get put in a "{...}" envelope, despite the release notes.
+
+ 7. The #token ">>" appearing in the DLG grammar description
+ causes DLG to generate the string literal "\>\>" which
+ is non-conforming and will cause some compilers to
+ complain (scan.c function act10 line 143 of source code).
+
+#11. (Version 1.32b6) Dave Kuhlman (dkuhlman@netcom.com)
+
+ Problem with file close in gen.c. Already fixed in 1.33.
+
+#10. (Version 1.32b6/29-Aug-95)
+
+ pccts/antlr/main.c contains a C++ style comments on lines 149
+ and 176 which causes problems for most C compilers.
+
+ Already fixed in 1.33.
+
+#9. (Version 1.32b4/14-Mar-95) dlgauto.h #include "config.h"
+
+ The file pccts/h/dlgauto.h should probably contain a #include
+ "config.h" as it uses the #define symbol __USE_PROTOS.
+
+ Added to 1.33MR1.
+
+#8. (Version 1.32b4/6-Mar-95) Michael T. Richter (mtr@igs.net)
+
+ In C++ output mode anonymous tokens from in-line regular expressions
+ can create enum values which are too wide for the datatype of the enum
+ assigned by the C++ compiler.
+
+ Fixed in 1.33MR1.
+
+#7. (Version 1.32b4/6-Mar-95) C++ does not imply __STDC__
+
+ In err.h the combination of # directives assumes that a C++
+ compiler has __STDC__ defined. This is not necessarily true.
+
+ This problem also appears in the use of __USE_PROTOS which
+ is appropriate for both Standard C and C++ in antlr/gen.c
+ and antlr/lex.c
+
+ Fixed in 1.33MR1.
+
+#6. (Version 1.32 ?/15-Feb-95) Name conflict for "TokenType"
+
+ Already fixed in 1.33.
+
+#5. (23-Jan-95) Douglas_Cuthbertson.JTIDS@jtids_qmail.hanscom.af.mil
+
+ The fail action following a semantic predicate is not enclosed in
+ "{...}". This can lead to problems when the fail action contains
+ more than one statement.
+
+ Fixed in 1.33MR1.
+
+#4 . (Version 1.33/31-Mar-96) jlilley@empathy.com (John Lilley)
+
+ Put briefly, a semantic predicate ought to abort a guess if it fails.
+
+ Correction suggested by J. Lilley has been added to 1.33MR1.
+
+#3 . (Version 1.33) P.A.Keller@bath.ac.uk
+
+ Extra commas are placed in the K&R style argument list for rules
+ when using both exceptions and ASTs.
+
+ Fixed in 1.33MR1.
+
+#2. (Version 1.32b6/2-Oct-95) Brad Schick <schick@interaccess.com>
+
+ Construct #[] generates zzastnew() in C++ mode.
+
+ Already fixed in 1.33.
+
+#1. (Version 1.33) Bob Bailey (robert@oakhill.sps.mot.com)
+
+ Previously, config.h assumed that all PC systems required
+ "short" file names. The user can now override that
+ assumption with "#define LONGFILENAMES".
+
+ Added to 1.33MR1.
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