From fab45b962749184e1a1a57c7c583782b78fad539 Mon Sep 17 00:00:00 2001 From: Sam James Date: Tue, 13 Aug 2024 20:49:06 +0100 Subject: [PATCH] libbpf: Workaround -Wmaybe-uninitialized false positive MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- tools/lib/bpf/elf.c | 3 +++ 1 file changed, 3 insertions(+) --- a/tools/lib/bpf/elf.c +++ b/tools/lib/bpf/elf.c @@ -16,6 +16,9 @@ int elf_open(const char *binary_path, st 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;