From nobody Sat Feb 7 08:44:58 2026 Received: from smtp.gentoo.org (woodpecker.gentoo.org [140.211.166.183]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B922170A10; Mon, 12 Aug 2024 10:39:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=140.211.166.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723459201; cv=none; b=s5V6aae5FvoiEu7QU5ZuibiOdgm043yG9V32eU8MR7etP1E8+yxWFGYVjPo839Y81bbGq+RPLF4L4Xm9VzPiGygLKVbUOP5cDYwo+U3Uvj5TuTxFZSJe1a3c3c6zplpLqjiz7B7LKK9qQAtOZoxusKMcuA+IiMzUFMyBJgAiODs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723459201; c=relaxed/simple; bh=xCsYDVX1SIMmI3WsGtCGKeTYuTPXPlKecf6vZhRK6yU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=fEpNtgYpXRBsRHvFe2GcJzBG0TRe31yX7uUOXg6vvM96ajpzUVSousW3aNUFjLzEj5Glh+0VycofddwOkb9G96fmjkQJfPAcPFZbi57MJ8vbNkVep9Q/iOzhsD88pVHdCSY6aUYs5HVzSwpY9qUfUzJbrBtcQ9OVkGg9Puh1QMw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gentoo.org; spf=pass smtp.mailfrom=gentoo.org; arc=none smtp.client-ip=140.211.166.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gentoo.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gentoo.org From: Sam James To: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: "Jose E . Marchesi" , Andrew Pinski , =?UTF-8?q?Kacper=20S=C5=82omi=C5=84ski?= , =?UTF-8?q?Arsen=20Arsenovi=C4=87?= , Sam James , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] libbpf: workaround -Wmaybe-uninitialized false positive Date: Mon, 12 Aug 2024 11:37:59 +0100 Message-ID: <12cec1262be71de5f1d9eae121b637041a5ae247.1723459079.git.sam@gentoo.org> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable In `elf_close`, we get this with GCC 15 -O3 (at least): ``` In function =E2=80=98elf_close=E2=80=99, inlined from =E2=80=98elf_close=E2=80=99 at elf.c:53:6, inlined from =E2=80=98elf_find_func_offset_from_file=E2=80=99 at elf.c:= 384:2: elf.c:57:9: warning: =E2=80=98elf_fd.elf=E2=80=99 may be used uninitialized= [-Wmaybe-uninitialized] 57 | elf_end(elf_fd->elf); | ^~~~~~~~~~~~~~~~~~~~ elf.c: In function =E2=80=98elf_find_func_offset_from_file=E2=80=99: elf.c:377:23: note: =E2=80=98elf_fd.elf=E2=80=99 was declared here 377 | struct elf_fd elf_fd; | ^~~~~~ In function =E2=80=98elf_close=E2=80=99, inlined from =E2=80=98elf_close=E2=80=99 at elf.c:53:6, inlined from =E2=80=98elf_find_func_offset_from_file=E2=80=99 at elf.c:= 384:2: elf.c:58:9: warning: =E2=80=98elf_fd.fd=E2=80=99 may be used uninitialized = [-Wmaybe-uninitialized] 58 | close(elf_fd->fd); | ^~~~~~~~~~~~~~~~~ elf.c: In function =E2=80=98elf_find_func_offset_from_file=E2=80=99: elf.c:377:23: note: =E2=80=98elf_fd.fd=E2=80=99 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.elf to -1. I've done this in two other functions as well given it could easily occur there too (same access/use pattern). Link: https://gcc.gnu.org/PR114952 Signed-off-by: Sam James Acked-by: Jiri Olsa Reviewed-by: Alan Maguire --- v3: Initialize to -1 instead of using a pragma. Range-diff against v2: 1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitiali= zed false positive -: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitiali= zed false positive tools/lib/bpf/elf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c index c92e02394159e..00ea3f867bbc8 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 *n= ame) { - struct elf_fd elf_fd; + struct elf_fd elf_fd =3D { .fd =3D -1 }; long ret =3D -ENOENT; =20 ret =3D elf_open(binary_path, &elf_fd); @@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, i= nt cnt, int err =3D 0, i, cnt_done =3D 0; unsigned long *offsets; struct symbol *symbols; - struct elf_fd elf_fd; + struct elf_fd elf_fd =3D { .fd =3D -1 }; =20 err =3D elf_open(binary_path, &elf_fd); if (err) @@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path= , const char *pattern, int sh_types[2] =3D { SHT_SYMTAB, SHT_DYNSYM }; unsigned long *offsets =3D NULL; size_t cap =3D 0, cnt =3D 0; - struct elf_fd elf_fd; + struct elf_fd elf_fd =3D { .fd =3D -1 }; int err =3D 0, i; =20 err =3D elf_open(binary_path, &elf_fd); --=20 2.45.2