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

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 e88ca24319e4 ("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: 9d7a0577c9db ("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>

diff --git a/Makefile b/Makefile
index 5aa9ee52a765b7aed27f44028cdcc34a90979acb..94be5dfb81fb3cbfc842c7b61b4e06f25f0f9c0f 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -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
 

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 2d6e59561c9d041895339c922c55545b883b0025..d88acdf4085524b672c69fb75148ee87c30f88d8 100644 (file)
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -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
 
 #