Date: Sat, 3 Feb 2024 19:23:57 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 9ed713d97b3d - main - cdefs: Introduce __result_use_or_ignore_check Message-ID: <202402031923.413JNvV5012351@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=9ed713d97b3d0376747c9ad1842864bebf08f823 commit 9ed713d97b3d0376747c9ad1842864bebf08f823 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2024-02-03 19:16:50 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2024-02-03 19:16:50 +0000 cdefs: Introduce __result_use_or_ignore_check Try to paper over inconsistent semantics for __warn_unused_result__ between clang and gcc. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 for a spirited discussion of these semantics. Introduce __result_use_or_ignore_check, which allows callers to explicitly ignore the return value with a cast to void. Use that to restore some checking for copyout() and friends, previously removed in commit d07acc58d898 ("systm: Relax __result_use_check annotations"). Reviewed by: olce, rpokala, kib, emaste MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D43426 --- sys/sys/cdefs.h | 11 +++++++++++ sys/sys/systm.h | 17 +++++++++-------- 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h index 206cc569c55a..e47a7072e1f1 100644 --- a/sys/sys/cdefs.h +++ b/sys/sys/cdefs.h @@ -326,6 +326,17 @@ #if __GNUC_PREREQ__(3, 4) #define __fastcall __attribute__((__fastcall__)) #define __result_use_check __attribute__((__warn_unused_result__)) +#ifdef __clang__ +/* + * clang and gcc have different semantics for __warn_unused_result__: the latter + * does not permit the use of a void cast to suppress the warning. Use + * __result_use_or_ignore_check in places where a void cast is acceptable. + * This can be implemented by [[nodiscard]] from C23. + */ +#define __result_use_or_ignore_check __result_use_check +#else +#define __result_use_or_ignore_check +#endif /* !__clang__ */ #else #define __fastcall #define __result_use_check diff --git a/sys/sys/systm.h b/sys/sys/systm.h index 29c8bfc3c768..376a35e7e8e2 100644 --- a/sys/sys/systm.h +++ b/sys/sys/systm.h @@ -299,10 +299,11 @@ int __result_use_check copyin(const void * __restrict udaddr, void * _Nonnull __restrict kaddr, size_t len); int __result_use_check copyin_nofault(const void * __restrict udaddr, void * _Nonnull __restrict kaddr, size_t len); -int copyout(const void * _Nonnull __restrict kaddr, - void * __restrict udaddr, size_t len); -int copyout_nofault(const void * _Nonnull __restrict kaddr, +int __result_use_or_ignore_check copyout(const void * _Nonnull __restrict kaddr, void * __restrict udaddr, size_t len); +int __result_use_or_ignore_check copyout_nofault( + const void * _Nonnull __restrict kaddr, void * __restrict udaddr, + size_t len); #ifdef SAN_NEEDS_INTERCEPTORS int SAN_INTERCEPTOR(copyin)(const void *, void *, size_t); @@ -323,11 +324,11 @@ int64_t fuword64(volatile const void *base); int __result_use_check fueword(volatile const void *base, long *val); int __result_use_check fueword32(volatile const void *base, int32_t *val); int __result_use_check fueword64(volatile const void *base, int64_t *val); -int subyte(volatile void *base, int byte); -int suword(volatile void *base, long word); -int suword16(volatile void *base, int word); -int suword32(volatile void *base, int32_t word); -int suword64(volatile void *base, int64_t word); +int __result_use_or_ignore_check subyte(volatile void *base, int byte); +int __result_use_or_ignore_check suword(volatile void *base, long word); +int __result_use_or_ignore_check suword16(volatile void *base, int word); +int __result_use_or_ignore_check suword32(volatile void *base, int32_t word); +int __result_use_or_ignore_check suword64(volatile void *base, int64_t word); uint32_t casuword32(volatile uint32_t *base, uint32_t oldval, uint32_t newval); u_long casuword(volatile u_long *p, u_long oldval, u_long newval); int casueword32(volatile uint32_t *base, uint32_t oldval, uint32_t *oldvalp,
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