MdePkg: Fix null macros for XCODE5 and CLANG

When building OvmfPkg in RELEASE mode in the XCODE5 toolchain, the
ASSERT_EFI_ERROR change prevents this error:

.../MdePkg/Library/UefiMemoryAllocationLib/MemoryAllocationLib.c:141:15:
error: variable 'Status' set but not used [-Werror,-Wunused-but-set-variable]
  EFI_STATUS  Status;
              ^

which is currently stopping the build.

When building in RELEASE mode in the CLANGPDB toolchain,the DEBUG macro
change prevents this error:

.../edk2/OvmfPkg/VirtioSerialDxe/VirtioSerial.c:28:22: error:
variable 'EventNames' is not needed and will not be
emitted [-Werror,-Wunneeded-internal-declaration]
STATIC CONST CHAR8  *EventNames[] = {
                     ^

which is currently stopping the build.

CLANGDWARF produces the same error as CLANGPDB above, if
-Wno-unneeded-internal-declaration is removed from its build flags.
With the null DEBUG macro change, this warning suppression
can be removed from CLANGDWARF, which is considered a benefit
as it has the potential to catch real coding errors. This is
done in a subsequent commit.

This commit has the desirable side effect that we no longer require
(and cannot use) explicit `#ifndef MDEPKG_NDEBUG` around items only
used in DEBUG macros. This requires the ArmPkg change made here to
be in the same commit as the MdePkg changes.

Note: In common with existing macros in EDK II, including the pre-existing
and unchanged DEBUG/NOOPT versions of the macros which are modified here,
we use the standard approach of adding `do { ... } while (FALSE)` wrapping
to ensure that the macros behave correctly with surrounding code
(e.g. require a following ';' and do not combine in unexpected ways with
nearby conditionals).

Continuous-integration-options: PatchCheck.ignore-multi-package
Co-authored-by: Mikhail Krichanov <krichanov@ispras.ru>
Signed-off-by: Mike Beaton <mjsbeaton@gmail.com>

1 files changed, 31 insertions, 4 deletions

diff --git a/MdePkg/Include/Library/DebugLib.h b/MdePkg/Include/Library/DebugLib.h
index 033c4e1a66..b48e08a7e4 100644
--- a/MdePkg/Include/Library/DebugLib.h
+++ b/MdePkg/Include/Library/DebugLib.h
@@ -8,6 +8,13 @@
   of size reduction when compiler optimization is disabled. If MDEPKG_NDEBUG is

   defined, then debug and assert related macros wrapped by it are the NULL implementations.

 

+  The implementations of the macros used when MDEPKG_NDEBUG is defined rely on the fact that

+  directly unreachable code is pruned, even with compiler optimization disabled (which has

+  been confirmed by generated code size tests on supported compilers). The advantage of

+  implementations which consume their arguments within directly unreachable code is that

+  compilers understand this, and stop warning about variables which would become unused when

+  MDEPKG_NDEBUG is defined if the macros had completely empty definitions.

+

 Copyright (c) 2006 - 2020, Intel Corporation. All rights reserved.<BR>

 SPDX-License-Identifier: BSD-2-Clause-Patent

 

@@ -403,7 +410,12 @@ UnitTestDebugAssert (
       }                             \

     } while (FALSE)

 #else

-#define ASSERT(Expression)

+#define ASSERT(Expression)       \

+    do {                           \

+      if (FALSE) {                 \

+        (VOID) (Expression);       \

+      }                            \

+    } while (FALSE)

 #endif

 

 /**

@@ -426,7 +438,12 @@ UnitTestDebugAssert (
       }                            \

     } while (FALSE)

 #else

-#define DEBUG(Expression)

+#define DEBUG(Expression)        \

+    do {                           \

+      if (FALSE) {                 \

+        _DEBUGLIB_DEBUG (Expression);       \

+      }                            \

+    } while (FALSE)

 #endif

 

 /**

@@ -452,7 +469,12 @@ UnitTestDebugAssert (
       }                                                                                  \

     } while (FALSE)

 #else

-#define ASSERT_EFI_ERROR(StatusParameter)

+#define ASSERT_EFI_ERROR(StatusParameter)                                             \

+    do {                                                                                \

+      if (FALSE) {                                                                      \

+        (VOID) (StatusParameter);                                                       \

+      }                                                                                 \

+    } while (FALSE)

 #endif

 

 /**

@@ -479,7 +501,12 @@ UnitTestDebugAssert (
       }                                                                 \

     } while (FALSE)

 #else

-#define ASSERT_RETURN_ERROR(StatusParameter)

+#define ASSERT_RETURN_ERROR(StatusParameter)                          \

+    do {                                                                \

+      if (FALSE) {                                                      \

+        (VOID) (StatusParameter);                                       \

+      }                                                                 \

+    } while (FALSE)

 #endif

 

 /**