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authorNick Desaulniers <ndesaulniers@google.com>2022-09-01 10:59:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-09-04 11:15:50 -0700
commitb0839b281c427e844143dba3893e25c83cdd6c17 (patch)
tree64b21a1f600a35a36dc1a1ba78bac0c89a5c8dd4 /scripts
parent7726d4c3e60bfe206738894267414a5f10510f1a (diff)
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Makefile.extrawarn: re-enable -Wformat for clang; take 2
-Wformat was recently re-enabled for builds with clang, then quickly re-disabled, due to concerns stemming from the frequency of default argument promotion related warning instances. commit 258fafcd0683 ("Makefile.extrawarn: re-enable -Wformat for clang") commit 21f9c8a13bb2 ("Revert "Makefile.extrawarn: re-enable -Wformat for clang"") ISO WG14 has ratified N2562 to address default argument promotion explicitly for printf, as part of the upcoming ISO C2X standard. The behavior of clang was changed in clang-16 to not warn for the cited cases in all language modes. Add a version check, so that users of clang-16 now get the full effect of -Wformat. For older clang versions, re-enable flags under the -Wformat group that way users still get some useful checks related to format strings, without noisy default argument promotion warnings. I intentionally omitted -Wformat-y2k and -Wformat-security from being re-enabled, which are also part of -Wformat in clang-16. Link: https://github.com/ClangBuiltLinux/linux/issues/378 Link: https://github.com/llvm/llvm-project/issues/57102 Link: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2562.pdf Suggested-by: Justin Stitt <jstitt007@gmail.com> Suggested-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: Youngmin Nam <youngmin.nam@samsung.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'scripts')
-rw-r--r--scripts/Makefile.extrawarn12
1 files changed, 12 insertions, 0 deletions
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 0621c39a3955..6ae482158bc4 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -47,7 +47,19 @@ else
ifdef CONFIG_CC_IS_CLANG
KBUILD_CFLAGS += -Wno-initializer-overrides
+# Clang before clang-16 would warn on default argument promotions.
+ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -lt 160000 ] && echo y),y)
+# Disable -Wformat
KBUILD_CFLAGS += -Wno-format
+# Then re-enable flags that were part of the -Wformat group that aren't
+# problematic.
+KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
+KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
+# Requires clang-12+.
+ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -ge 120000 ] && echo y),y)
+KBUILD_CFLAGS += -Wformat-insufficient-args
+endif
+endif
KBUILD_CFLAGS += -Wno-sign-compare
KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare