From patchwork Fri Aug 9 17:26:41 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sam James X-Patchwork-Id: 13759031 X-Patchwork-Delegate: bpf@iogearbox.net 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 B565818AF9; Fri, 9 Aug 2024 17:27:06 +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=1723224428; cv=none; b=bW+y2kO00UfxVHj8XiF8tfGRG9ceh1caIZDH+uquxb6PTweC+FscaKtxi+ZOCxay5wp83CFvMELpJrTq1yz5lsRdViXVsM+jpq0xdIoWnN6kANS/0hjPDP5iaajZSdRYqB/sAUTp2VsuWnmR2RDcOSt9z9+mh+JOe8tZElQB/jc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723224428; c=relaxed/simple; bh=UEMJSCPC06mX95wMv+b6VRAuDY2cK9dt0+DdZbnB0Q0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=MY++RP3u0EOp6IkOr6N+1dq7oV1agBLtCCZOTRf/09IlIWoO8TrSip6zCS0YzhW2p04Z/JuZM+QCys7b8DOTe1vLF88D1TY1A1qNSiCNjFJ8YFeRp6pyCeutgdtGzcJeu3y4BjKpf0eouSfkogd8Kefq46kdRfF21qrMHAQLsRE= 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: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Cc: "Jose E . Marchesi" , Andrew Pinski , =?utf-8?b?S2FjcGVyIFPFgm9tacWE?= =?utf-8?b?c2tp?= , =?utf-8?q?Arsen_Arsenovi?= =?utf-8?q?=C4=87?= , Sam James , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH v2] libbpf: workaround -Wmaybe-uninitialized false positive Date: Fri, 9 Aug 2024 18:26:41 +0100 Message-ID: <8f5c3b173e4cb216322ae19ade2766940c6fbebb.1723224401.git.sam@gentoo.org> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 --- 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;