Messages in this thread Patch in this message | | | Date | Fri, 25 Jun 2021 22:52:26 +0300 | From | Alexey Dobriyan <> | Subject | [PATCH] ELF: add and use SUPRESS_WARN_UNUSED_RESULT |
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Last write to the "error" variable in load_elf_binary() is dead write.
Add and use SUPRESS_WARN_UNUSED_RESULT macro to express intent better.
Credit goes to Ed Catmur:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425#c34
Macro doesn't work for WUR functions returning structures and unions, but it will work once gcc copies clang.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> ---
fs/binfmt_elf.c | 3 ++- include/linux/compiler_attributes.h | 4 ++++ 2 files changed, 6 insertions(+), 1 deletion(-)
--- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1290,7 +1290,8 @@ static int load_elf_binary(struct linux_binprm *bprm) and some applications "depend" upon this behavior. Since we do not have the power to recompile these, we emulate the SVr4 behavior. Sigh. */ - error = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EXEC, + SUPRESS_WARN_UNUSED_RESULT + vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE, 0); } --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -284,6 +284,10 @@ * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result */ #define __must_check __attribute__((__warn_unused_result__)) +/* + * "(void)" is enough for clang but not for gcc. + */ +#define SUPRESS_WARN_UNUSED_RESULT (void)! /* * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
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