From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03DE5C3DA7B for ; Sun, 18 Dec 2022 16:53:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232888AbiLRQxT (ORCPT ); Sun, 18 Dec 2022 11:53:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233051AbiLRQwb (ORCPT ); Sun, 18 Dec 2022 11:52:31 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 12E4E11838; Sun, 18 Dec 2022 08:18:31 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id CC464B80BAA; Sun, 18 Dec 2022 16:18:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC739C433EF; Sun, 18 Dec 2022 16:18:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1671380302; bh=cy62qzUXmxJDIjtBNB+9WcseOi5CuKs9U+vaJzf7JtI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bk+GtxgSt0LEre6cX7NwNZnyCaXE+ESKN/2+61+Exaqnd6vPqFlOlPMsqLd7R61+E h+OZHyNFX8B2/L4IGFZOPR0FNdPh9bPh+EcZ37o5pPtYwnWSW+VWTl3V2AP6eX1pTn 9FlXY4Z8L6lSwb9KWpoiaSQttx1KK8Ku7JLFuty7iyocHUR9kBuQ8zNHW/51ftg6Nn IGk7EUyRmqLDvNgQWs2lI6hL6qvRrNOfH3P7F9RUk11antjWALD41kFaU3GgclutkP UL2q8pezt1OF4v315Z3o422Z90jiz/SX8OWEiR2aQKsIC5QleoFBU0qqnSBxbVWUtg GAS/osU48XiUg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrii Nakryiko , Daniel Borkmann , Sasha Levin , ast@kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 34/39] libbpf: Avoid enum forward-declarations in public API in C++ mode Date: Sun, 18 Dec 2022 11:15:54 -0500 Message-Id: <20221218161559.932604-34-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221218161559.932604-1-sashal@kernel.org> References: <20221218161559.932604-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrii Nakryiko [ Upstream commit b42693415b86f608049cf1b4870adc1dc65e58b0 ] C++ enum forward declarations are fundamentally not compatible with pure C enum definitions, and so libbpf's use of `enum bpf_stats_type;` forward declaration in libbpf/bpf.h public API header is causing C++ compilation issues. More details can be found in [0], but it comes down to C++ supporting enum forward declaration only with explicitly specified backing type: enum bpf_stats_type: int; In C (and I believe it's a GCC extension also), such forward declaration is simply: enum bpf_stats_type; Further, in Linux UAPI this enum is defined in pure C way: enum bpf_stats_type { BPF_STATS_RUN_TIME = 0; } And even though in both cases backing type is int, which can be confirmed by looking at DWARF information, for C++ compiler actual enum definition and forward declaration are incompatible. To eliminate this problem, for C++ mode define input argument as int, which makes enum unnecessary in libbpf public header. This solves the issue and as demonstrated by next patch doesn't cause any unwanted compiler warnings, at least with default warnings setting. [0] https://stackoverflow.com/questions/42766839/c11-enum-forward-causes-underlying-type-mismatch [1] Closes: https://github.com/libbpf/libbpf/issues/249 Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20221130200013.2997831-1-andrii@kernel.org Signed-off-by: Sasha Levin --- tools/lib/bpf/bpf.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 875dde20d56e..92a3eaa154dd 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -241,8 +241,15 @@ LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf, __u32 *buf_len, __u32 *prog_id, __u32 *fd_type, __u64 *probe_offset, __u64 *probe_addr); +#ifdef __cplusplus +/* forward-declaring enums in C++ isn't compatible with pure C enums, so + * instead define bpf_enable_stats() as accepting int as an input + */ +LIBBPF_API int bpf_enable_stats(int type); +#else enum bpf_stats_type; /* defined in up-to-date linux/bpf.h */ LIBBPF_API int bpf_enable_stats(enum bpf_stats_type type); +#endif struct bpf_prog_bind_opts { size_t sz; /* size of this struct for forward/backward compatibility */ -- 2.35.1