6.14-stable review patch. If anyone has any objections, please let me know.
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From: Linus Torvalds torvalds@linux-foundation.org
commit d5d45a7f26194460964eb5677a9226697f7b7fdd upstream.
gcc-15 enabling -Wunterminated-string-initialization in -Wextra by default was done with the best intentions, but the warning is still quite broken.
What annoys me about the warning is that this is a very traditional AND CORRECT way to initialize fixed byte arrays in C:
unsigned char hex[16] = "0123456789abcdef";
and we use this all over the kernel. And the warning is fine, but gcc developers apparently never made a reasonable way to disable it. As is (sadly) tradition with these things.
Yes, there's "__attribute__((nonstring))", and we have a macro to make that absolutely disgusting syntax more palatable (ie the kernel syntax for that monstrosity is just "__nonstring").
But that attribute is misdesigned. What you'd typically want to do is tell the compiler that you are using a type that isn't a string but a byte array, but that doesn't work at all:
warning: ‘nonstring’ attribute does not apply to types [-Wattributes]
and because of this fundamental mis-design, you then have to mark each instance of that pattern.
This is particularly noticeable in our ACPI code, because ACPI has this notion of a 4-byte "type name" that gets used all over, and is exactly this kind of byte array.
This is a sad oversight, because the warning is useful, but really would be so much better if gcc had also given a sane way to indicate that we really just want a byte array type at a type level, not the broken "each and every array definition" level.
So now instead of creating a nice "ACPI name" type using something like
typedef char acpi_name_t[4] __nonstring;
we have to do things like
char name[ACPI_NAMESEG_SIZE] __nonstring;
in every place that uses this concept and then happens to have the typical initializers.
This is annoying me mainly because I think the warning _is_ a good warning, which is why I'm not just turning it off in disgust. But it is hampered by this bad implementation detail.
[ And obviously I'm doing this now because system upgrades for me are something that happen in the middle of the release cycle: don't do it before or during travel, or just before or during the busy merge window period. ]
Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Makefile | 3 +++ 1 file changed, 3 insertions(+)
--- a/Makefile +++ b/Makefile @@ -1053,6 +1053,9 @@ KBUILD_CFLAGS += $(call cc-option, -fstr KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow) KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
+#Currently, disable -Wunterminated-string-initialization as an error +KBUILD_CFLAGS += $(call cc-option, -Wno-error=unterminated-string-initialization) + # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += -fno-strict-overflow