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kbuild: Properly disable -Wunterminated-string-initialization for clang

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Clang and GCC have different behaviors around disabling warnings
included in -Wall and -Wextra and the order in which flags are
specified, which is exposed by clang's new support for
-Wunterminated-string-initialization.

  $ cat test.c
  const char foo[3] = "FOO";
  const char bar[3] __attribute__((__nonstring__)) = "BAR";

  $ clang -fsyntax-only -Wextra test.c
  test.c:1:21: warning: initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
      1 | const char foo[3] = "FOO";
        |                     ^~~~~
  $ clang -fsyntax-only -Wextra -Wno-unterminated-string-initialization test.c
  $ clang -fsyntax-only -Wno-unterminated-string-initialization -Wextra test.c
  test.c:1:21: warning: initializer-string for character array is too long, array size is 3 but initializer has size 4 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Wunterminated-string-initialization]
      1 | const char foo[3] = "FOO";
        |                     ^~~~~

  $ gcc -fsyntax-only -Wextra test.c
  test.c:1:21: warning: initializer-string for array of ‘char’ truncates NUL terminator but destination lacks ‘nonstring’ attribute (4 chars into 3 available) [-Wunterminated-string-initialization]
      1 | const char foo[3] = "FOO";
        |                     ^~~~~
  $ gcc -fsyntax-only -Wextra -Wno-unterminated-string-initialization test.c
  $ gcc -fsyntax-only -Wno-unterminated-string-initialization -Wextra test.c

Move -Wextra up right below -Wall in Makefile.extrawarn to ensure these
flags are at the beginning of the warning options list. Move the couple
of warning options that have been added to the main Makefile since
commit e88ca24319 ("kbuild: consolidate warning flags in
scripts/Makefile.extrawarn") to scripts/Makefile.extrawarn after -Wall /
-Wextra to ensure they get properly disabled for all compilers.

Fixes: 9d7a0577c9 ("gcc-15: disable '-Wunterminated-string-initialization' entirely for now")
Link: https://github.com/llvm/llvm-project/issues/10359
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nathan Chancellor 2025-04-30 15:56:34 -07:00 committed by Linus Torvalds
parent 7a13c14ee5
commit 4f79eaa2ce
2 changed files with 8 additions and 8 deletions
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7
Makefile
View File

@ -1052,13 +1052,6 @@ NOSTDINC_FLAGS += -nostdinc
# perform bounds checking.
KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
#Currently, disable -Wstringop-overflow for GCC 11, globally.
KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-disable-warning, stringop-overflow)
KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
#Currently, disable -Wunterminated-string-initialization as broken
KBUILD_CFLAGS += $(call cc-disable-warning, unterminated-string-initialization)
# disable invalid "can't wrap" optimizations for signed / pointers
KBUILD_CFLAGS += -fno-strict-overflow

9
scripts/Makefile.extrawarn
View File

@ -8,6 +8,7 @@
# Default set of warnings, always enabled
KBUILD_CFLAGS += -Wall
KBUILD_CFLAGS += -Wextra
KBUILD_CFLAGS += -Wundef
KBUILD_CFLAGS += -Werror=implicit-function-declaration
KBUILD_CFLAGS += -Werror=implicit-int
@ -56,6 +57,13 @@ KBUILD_CFLAGS += -Wno-pointer-sign
# globally built with -Wcast-function-type.
KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
# Currently, disable -Wstringop-overflow for GCC 11, globally.
KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-disable-warning, stringop-overflow)
KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
# Currently, disable -Wunterminated-string-initialization as broken
KBUILD_CFLAGS += $(call cc-disable-warning, unterminated-string-initialization)
# The allocators already balk at large sizes, so silence the compiler
# warnings for bounds checks involving those possible values. While
# -Wno-alloc-size-larger-than would normally be used here, earlier versions
@ -82,7 +90,6 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
# Warn if there is an enum types mismatch
KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
KBUILD_CFLAGS += -Wextra
KBUILD_CFLAGS += -Wunused
#