On 09/08/2024 18:26, Sam James wrote: > In `elf_close`, we get this with GCC 15 -O3 (at least): > ``` > In function ‘elf_close’, > inlined from ‘elf_close’ at elf.c:53:6, > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: > elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized] > 57 | elf_end(elf_fd->elf); > | ^~~~~~~~~~~~~~~~~~~~ > elf.c: In function ‘elf_find_func_offset_from_file’: > elf.c:377:23: note: ‘elf_fd.elf’ was declared here > 377 | struct elf_fd elf_fd; > | ^~~~~~ > In function ‘elf_close’, > inlined from ‘elf_close’ at elf.c:53:6, > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: > elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized] > 58 | close(elf_fd->fd); > | ^~~~~~~~~~~~~~~~~ > elf.c: In function ‘elf_find_func_offset_from_file’: > elf.c:377:23: note: ‘elf_fd.fd’ was declared here > 377 | struct elf_fd elf_fd; > | ^~~~~~ > ``` > > In reality, our use is fine, it's just that GCC doesn't model errno > here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly. > > Link: https://gcc.gnu.org/PR114952 > Signed-off-by: Sam James <sam@xxxxxxxxxx> > --- > v2: Fix Clang build. > > Range-diff against v1: > 1: 3ebbe7a4e93a ! 1: 8f5c3b173e4c libbpf: workaround -Wmaybe-uninitialized false positive > @@ tools/lib/bpf/elf.c: long elf_find_func_offset(Elf *elf, const char *binary_path > return ret; > } > > ++#if !defined(__clang__) > +#pragma GCC diagnostic push > +/* https://gcc.gnu.org/PR114952 */ > +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized" > ++#endif > /* Find offset of function name in ELF object specified by path. "name" matches > * symbol name or name@@LIB for library functions. > */ > @@ tools/lib/bpf/elf.c: long elf_find_func_offset_from_file(const char *binary_path > elf_close(&elf_fd); > return ret; > } > ++#if !defined(__clang__) > +#pragma GCC diagnostic pop > ++#endif > > struct symbol { > const char *name; > > tools/lib/bpf/elf.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c > index c92e02394159..7058425ca85b 100644 > --- a/tools/lib/bpf/elf.c > +++ b/tools/lib/bpf/elf.c > @@ -369,6 +369,11 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name) > return ret; > } > > +#if !defined(__clang__) > +#pragma GCC diagnostic push > +/* https://gcc.gnu.org/PR114952 */ > +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized" > +#endif > /* Find offset of function name in ELF object specified by path. "name" matches > * symbol name or name@@LIB for library functions. > */ > @@ -384,6 +389,9 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name) > elf_close(&elf_fd); > return ret; > } > +#if !defined(__clang__) > +#pragma GCC diagnostic pop > +#endif > > struct symbol { > const char *name; Would just initializing struct elf_fd be enough to silence the error perhaps, i.e. diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c index c92e02394159..3060597a527e 100644 --- a/tools/lib/bpf/elf.c +++ b/tools/lib/bpf/elf.c @@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name) */ long elf_find_func_offset_from_file(const char *binary_path, const char *name) { - struct elf_fd elf_fd; + struct elf_fd elf_fd = { .fd = -1 }; long ret = -ENOENT; ret = elf_open(binary_path, &elf_fd);
