From 531108ec5b5cd45ec6272a6115e73275baef7d22 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 12 Sep 2023 19:23:21 +0300 Subject: uapi: stddef.h: Fix header guard location The #endif for the header guard wasn't at the end of the header. This was harmless since the define that escaped was already testing for its own redefinition. Regardless, move the #endif to the correct place. Signed-off-by: Alexey Dobriyan Fixes: c8248faf3ca2 ("Compiler Attributes: counted_by: Adjust name and identifier expansion") Link: https://lore.kernel.org/r/b1f5081e-339d-421d-81b2-cbb94e1f6f5f@p183 Co-developed-by: Kees Cook Signed-off-by: Kees Cook --- include/uapi/linux/stddef.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h index 7c3fc3980881..c027b2070d79 100644 --- a/include/uapi/linux/stddef.h +++ b/include/uapi/linux/stddef.h @@ -44,8 +44,9 @@ struct { } __empty_ ## NAME; \ TYPE NAME[]; \ } -#endif #ifndef __counted_by #define __counted_by(m) #endif + +#endif /* _UAPI_LINUX_STDDEF_H */ -- cgit v1.2.3 From 32a4ec211d4164e667d9d0b807fadf02053cd2e9 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 12 Sep 2023 19:22:24 +0300 Subject: uapi: stddef.h: Fix __DECLARE_FLEX_ARRAY for C++ __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 to T member[]; Now g++ doesn't like "T member[]" either, throwing errors on the following code: struct S { union { T1 member1[]; T2 member2[]; }; }; or struct S { T member[]; }; Use "T member[0];" which seems to work and does the right thing wrt structure layout. Signed-off-by: Alexey Dobriyan Fixes: 3080ea5553cc ("stddef: Introduce DECLARE_FLEX_ARRAY() helper") Link: https://lore.kernel.org/r/97242381-f1ec-4a4a-9472-1a464f575657@p183 Signed-off-by: Kees Cook --- include/uapi/linux/stddef.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h index c027b2070d79..5c6c4269f7ef 100644 --- a/include/uapi/linux/stddef.h +++ b/include/uapi/linux/stddef.h @@ -29,6 +29,11 @@ struct TAG { MEMBERS } ATTRS NAME; \ } +#ifdef __cplusplus +/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */ +#define __DECLARE_FLEX_ARRAY(T, member) \ + T member[0] +#else /** * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union * @@ -44,6 +49,7 @@ struct { } __empty_ ## NAME; \ TYPE NAME[]; \ } +#endif #ifndef __counted_by #define __counted_by(m) -- cgit v1.2.3