From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.ilvokhin.com (mail.ilvokhin.com [178.62.254.231]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 093564C8FFD for ; Fri, 5 Jun 2026 11:31:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.62.254.231 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780659070; cv=none; b=tBCVfvjAMQpn8CReU2mz1eGasJL7Ic7ejilh4oue92yU7wQpceN+EzbtxbztydoHqcSyOxBmXgWE8CC1BmbCosiOqDOb7wkwU05csRAIO1nngD6l0COF6MiJBNkg6Ojt0c/hH+FNltM8KMckkfVy5Ihwlyr1rNuMsZXjFX7TALA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780659070; c=relaxed/simple; bh=mHSvhLilcJ8VuFuqcd9tocuM4VOBzDhKMKT4YE+07iw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=TYgaXidGD2+w4eCznCorGYGb7z6U8IC42KD3Rq0sd5r2Wjl4eZTBpixWqJ2nccwe/mybUusPam9a/01WF4u4/t0lknVBLCcuNqbQzoKNDMFQBMPg7VKvzWSZUs+IDXzQDOMVqtwSEuz5ROhGQ6GykoqArMgfLDKHEPzUmNvFgOU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ilvokhin.com; spf=pass smtp.mailfrom=ilvokhin.com; dkim=pass (1024-bit key) header.d=ilvokhin.com header.i=@ilvokhin.com header.b=ShoIPYDv; arc=none smtp.client-ip=178.62.254.231 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ilvokhin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ilvokhin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ilvokhin.com header.i=@ilvokhin.com header.b="ShoIPYDv" Received: from localhost.localdomain (shell.ilvokhin.com [138.68.190.75]) (Authenticated sender: d@ilvokhin.com) by mail.ilvokhin.com (Postfix) with ESMTPSA id 46FBDD120D; Fri, 05 Jun 2026 11:31:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ilvokhin.com; s=mail; t=1780659067; bh=/tUOK+mEotLDa1FWbzPQ301or5GmuZa1h3jo9htUyrA=; h=From:To:Cc:Subject:Date; b=ShoIPYDvWR8M/XGZG1ElZowrRH23hZXqt36TjcSWeyQnxkv8DMEaJZ7mAvFLAiYm4 Llop/KRQYk5P14BVB1hMvRR6GE5xxrf+rzqu3zjKkp9GXBCFbjLIAePS+XxmcftQhE 7+4oxbQC8IAm66R1s9B1zh5a6EcdykoeiIRNsevM= From: Dmitry Ilvokhin To: Chris Li Cc: linux-sparse@vger.kernel.org, Dmitry Ilvokhin , Dan Carpenter Subject: [PATCH] accept an empty attribute argument list Date: Fri, 5 Jun 2026 11:30:45 +0000 Message-ID: <20260605113045.483498-1-d@ilvokhin.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-sparse@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit GCC and clang accept an empty argument list for attributes, e.g. __attribute__((nonnull())), and treat it the same as the bare __attribute__((nonnull)). sparse instead rejects it with "an expression is expected before ')'". ignore_attribute() and recover_unknown_attribute() consume the optional argument list with parens_expression(), which requires a non-empty expression, so an empty () is rejected. The bare form is fine because it takes no parentheses and skips that path. This turned up in the Linux kernel: the cleanup.h guard macros expand __nonnull_args() to __attribute__((__nonnull__())). https://lore.kernel.org/all/aiJi0WcYE8FZt-jO@stanley.mountain/ Reported-by: Dan Carpenter Signed-off-by: Dmitry Ilvokhin --- parse.c | 17 +++++++++++++---- validation/attribute-nonnull-empty.c | 12 ++++++++++++ 2 files changed, 25 insertions(+), 4 deletions(-) create mode 100644 validation/attribute-nonnull-empty.c diff --git a/parse.c b/parse.c index 9389079e..3b380156 100644 --- a/parse.c +++ b/parse.c @@ -1106,8 +1106,13 @@ static struct token *autotype_specifier(struct token *token, struct symbol *sym, static struct token *ignore_attribute(struct token *token, struct symbol *attr, struct decl_state *ctx) { struct expression *expr = NULL; - if (match_op(token, '(')) - token = parens_expression(token, &expr, "in attribute"); + if (match_op(token, '(')) { + /* Accept an empty argument list, e.g. __attribute__((nonnull())) */ + if (match_op(token->next, ')')) + token = token->next->next; + else + token = parens_expression(token, &expr, "in attribute"); + } return token; } @@ -1362,8 +1367,12 @@ static struct token *recover_unknown_attribute(struct token *token) if (Wunknown_attribute) warning(token->pos, "unknown attribute '%s'", show_ident(token->ident)); token = token->next; - if (match_op(token, '(')) - token = parens_expression(token, &expr, "in attribute"); + if (match_op(token, '(')) { + if (match_op(token->next, ')')) + token = token->next->next; + else + token = parens_expression(token, &expr, "in attribute"); + } return token; } diff --git a/validation/attribute-nonnull-empty.c b/validation/attribute-nonnull-empty.c new file mode 100644 index 00000000..c4021f61 --- /dev/null +++ b/validation/attribute-nonnull-empty.c @@ -0,0 +1,12 @@ +/* + * An empty attribute argument list, like __attribute__((nonnull())), is + * accepted by GCC and Clang (equivalent to the bare __attribute__((nonnull))) + * and must be parsed by sparse too. + */ +extern void *bare (void *d, const void *s) __attribute__((nonnull)); +extern void *empty(void *d, const void *s) __attribute__((nonnull())); +extern void *args (void *d, const void *s) __attribute__((nonnull(1, 2))); + +/* + * check-name: attribute with empty argument list + */ -- 2.53.0-Meta