From: Sam James Date: Tue, 13 Aug 2024 19:49:06 +0000 (+0100) Subject: libbpf: Workaround -Wmaybe-uninitialized false positive X-Git-Tag: v6.12-rc1~112^2~88 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fab45b962749184e1a1a57c7c583782b78fad539;p=thirdparty%2Fkernel%2Flinux.git libbpf: Workaround -Wmaybe-uninitialized false positive 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 by initializing elf_fd.fd to -1 and elf_fd.elf to NULL. I've done this in two other functions as well given it could easily occur there too (same access/use pattern). Signed-off-by: Sam James Signed-off-by: Andrii Nakryiko Link: https://gcc.gnu.org/PR114952 Link: https://lore.kernel.org/bpf/14ec488a1cac02794c2fa2b83ae0cef1bce2cb36.1723578546.git.sam@gentoo.org --- diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c index c92e02394159e..b5ab1cb13e5ea 100644 --- a/tools/lib/bpf/elf.c +++ b/tools/lib/bpf/elf.c @@ -28,6 +28,9 @@ int elf_open(const char *binary_path, struct elf_fd *elf_fd) int fd, ret; Elf *elf; + elf_fd->elf = NULL; + elf_fd->fd = -1; + if (elf_version(EV_CURRENT) == EV_NONE) { pr_warn("elf: failed to init libelf for %s\n", binary_path); return -LIBBPF_ERRNO__LIBELF;