From: Alexey Dobriyan <adobriyan@gmail.com>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
keescook@chromium.org
Subject: [PATCH] uapi: partially fix __DECLARE_FLEX_ARRAY for C++
Date: Fri, 8 Sep 2023 14:32:24 +0300 [thread overview]
Message-ID: <930c3ee5-1282-40f4-93e0-8ff894aabf3a@p183> (raw)
__DECLARE_FLEX_ARRAY(T, member) macro expands to
struct {
struct {} __empty_member;
T member[];
};
which is subtly wrong in C++ because sizeof(struct{}) is 1 not 0,
changing UAPI structures layouts.
This can be fixed by expanding simply to
T member[];
Most of the usages still be broken because of other C++ shenanigans
but this fixes simplest usage: 1 flexible member at the end.
Fix header guard while I'm at it.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
include/uapi/linux/stddef.h | 6 ++++++
1 file changed, 6 insertions(+)
--- a/include/uapi/linux/stddef.h
+++ b/include/uapi/linux/stddef.h
@@ -39,6 +39,10 @@
* struct, it needs to be wrapped in an anonymous struct with at least 1
* named member, but that member can be empty.
*/
+#ifdef __cplusplus
+#define __DECLARE_FLEX_ARRAY(T, member) \
+ T member[]
+#else
#define __DECLARE_FLEX_ARRAY(TYPE, NAME) \
struct { \
struct { } __empty_ ## NAME; \
@@ -49,3 +53,5 @@
#ifndef __counted_by
#define __counted_by(m)
#endif
+
+#endif
next reply other threads:[~2023-09-08 11:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-08 11:32 Alexey Dobriyan [this message]
2023-09-08 15:14 ` [PATCH v2] uapi: fix __DECLARE_FLEX_ARRAY for C++ Alexey Dobriyan
2023-09-08 15:53 ` Kees Cook
2023-09-08 16:03 ` Alexey Dobriyan
2023-09-08 16:11 ` Kees Cook
2023-09-11 8:19 ` David Laight
2023-09-12 15:06 ` Alexey Dobriyan
2023-09-12 16:22 ` [PATCH v3 1/2] " Alexey Dobriyan
2023-09-12 16:23 ` [PATCH v3 2/2] uapi: fix header guard in include/uapi/linux/stddef.h Alexey Dobriyan
2023-09-15 19:14 ` [PATCH v3 1/2] uapi: fix __DECLARE_FLEX_ARRAY for C++ Kees Cook
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