Date: Sat, 12 Jul 2025 13:07:28 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: ba0d9b43e940 - main - kern_descrip.c: provide helpers to translate between fd flags namespace Message-ID: <85f6ca74-b557-4658-93a0-62774d7da196@FreeBSD.org> In-Reply-To: <aHFfQnpM3LkxByRm@kib.kiev.ua> References: <202507082149.568LnGOU086303@gitrepo.freebsd.org> <c9bde9bb-c914-4401-aff6-cc830944b0d6@FreeBSD.org> <aHFfQnpM3LkxByRm@kib.kiev.ua>
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On 7/11/25 15:00, Konstantin Belousov wrote: > On Fri, Jul 11, 2025 at 11:46:33AM -0400, John Baldwin wrote: >> On 7/8/25 17:49, Konstantin Belousov wrote: >>> The branch main has been updated by kib: >>> >>> URL: https://cgit.FreeBSD.org/src/commit/?id=ba0d9b43e940077f4025e7e4e85d16c8d525db79 >>> >>> commit ba0d9b43e940077f4025e7e4e85d16c8d525db79 >>> Author: Konstantin Belousov <kib@FreeBSD.org> >>> AuthorDate: 2025-07-08 16:30:29 +0000 >>> Commit: Konstantin Belousov <kib@FreeBSD.org> >>> CommitDate: 2025-07-08 21:48:59 +0000 >>> >>> kern_descrip.c: provide helpers to translate between fd flags namespace >>> Reviewed by: markj >>> Sponsored by: The FreeBSD Foundation >>> Differential revision: https://reviews.freebsd.org/D51206 >>> --- >>> sys/kern/kern_descrip.c | 110 +++++++++++++++++++++++++++++++++++++++--------- >>> 1 file changed, 90 insertions(+), 20 deletions(-) >>> >>> diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c >>> index 406236fc2723..2e1da2fdee29 100644 >>> --- a/sys/kern/kern_descrip.c >>> +++ b/sys/kern/kern_descrip.c >>> @@ -480,6 +480,90 @@ kern_fcntl_freebsd(struct thread *td, int fd, int cmd, intptr_t arg) >>> return (error); >>> } >>> +struct flags_trans_elem { >>> + u_int f; >>> + u_int t; >>> +}; >>> + >>> +static u_int >>> +flags_trans(const struct flags_trans_elem *ftes, int nitems, u_int from_flags) >>> +{ >>> + u_int res; >>> + int i; >>> + >>> + res = 0; >>> + for (i = 0; i < nitems; i++) { >>> + if ((from_flags & ftes[i].f) != 0) >>> + res |= ftes[i].t; >>> + } >>> + return (res); >>> +} >>> + >>> +static uint8_t >>> +fd_to_fde_flags(int fd_flags) >>> +{ >>> + static const struct flags_trans_elem fd_to_fde_flags_s[] = { >>> + { .f = FD_CLOEXEC, .t = UF_EXCLOSE }, >>> + { .f = FD_CLOFORK, .t = UF_FOCLOSE }, >>> + { .f = FD_RESOLVE_BENEATH, .t = UF_RESOLVE_BENEATH }, >>> + }; >>> + >>> + return (flags_trans(fd_to_fde_flags_s, nitems(fd_to_fde_flags_s), >>> + fd_flags)); >>> +} >>> + >>> +static int >>> +fde_to_fd_flags(uint8_t fde_flags) >>> +{ >>> + static const struct flags_trans_elem fde_to_fd_flags_s[] = { >>> + { .f = UF_EXCLOSE, .t = FD_CLOEXEC }, >>> + { .f = UF_FOCLOSE, .t = FD_CLOFORK }, >>> + { .f = UF_RESOLVE_BENEATH, .t = FD_RESOLVE_BENEATH }, >>> + }; >>> + >>> + return (flags_trans(fde_to_fd_flags_s, nitems(fde_to_fd_flags_s), >>> + fde_flags)); >>> +} >>> + >>> +static uint8_t >>> +fddup_to_fde_flags(int fddup_flags) >>> +{ >>> + static const struct flags_trans_elem fddup_to_fde_flags_s[] = { >>> + { .f = FDDUP_FLAG_CLOEXEC, .t = UF_EXCLOSE }, >>> + { .f = FDDUP_FLAG_CLOFORK, .t = UF_FOCLOSE }, >>> + }; >>> + >>> + return (flags_trans(fddup_to_fde_flags_s, nitems(fddup_to_fde_flags_s), >>> + fddup_flags)); >>> +} >>> + >>> +static uint8_t >>> +close_range_to_fde_flags(int close_range_flags) >>> +{ >>> + static const struct flags_trans_elem close_range_to_fde_flags_s[] = { >>> + { .f = CLOSE_RANGE_CLOEXEC, .t = UF_EXCLOSE }, >>> + { .f = CLOSE_RANGE_CLOFORK, .t = UF_FOCLOSE }, >>> + }; >>> + >>> + return (flags_trans(close_range_to_fde_flags_s, >>> + nitems(close_range_to_fde_flags_s), close_range_flags)); >>> +} >>> + >>> +static uint8_t >>> +open_to_fde_flags(int open_flags, bool sticky_orb) >>> +{ >>> + static const struct flags_trans_elem open_to_fde_flags_s[] = { >>> + { .f = O_CLOEXEC, .t = UF_EXCLOSE }, >>> + { .f = O_CLOFORK, .t = UF_FOCLOSE }, >>> + { .f = O_RESOLVE_BENEATH, .t = UF_RESOLVE_BENEATH }, >>> + }; >>> + _Static_assert(open_to_fde_flags_s[nitems(open_to_fde_flags_s) - 1].f == >>> + O_RESOLVE_BENEATH, "O_RESOLVE_BENEATH must be last, for sticky_orb"); >> >> This broke the GCC builds it seems. GCC doesn't think that it can compute this >> expression at compile time. >> >> From https://ci.freebsd.org/job/FreeBSD-main-amd64-gcc14_build/1022/console: >> >> 10:32:02 /workspace/src/sys/kern/kern_descrip.c: In function 'open_to_fde_flags': >> 10:32:02 /workspace/src/sys/kern/kern_descrip.c:560:79: error: expression in static = >> 10:32:02 assertion is not constant >> 10:32:02 560 | _Static_assert(open_to_fde_flags_s[nitems(open_to_fde_flags= >> 10:32:02 _s) - 1].f =3D=3D >> > > I am unable to propose anything better than the patch below. We have enough > #ifdef __clang__ in non-contrib sources already, so this should be not a > huge crime? > > % rg -g '!contrib/*' __clang__ | wc -l > 171 > > commit 96e6b15b0a1407af45ebe1ad38ee53627d09d16b > Author: Konstantin Belousov <kib@FreeBSD.org> > Date: Fri Jul 11 21:57:32 2025 +0300 > > kern_descrip.c: only allow complex expression in Static_assert() for clang > > gcc cannot compute the assert expression. > > Reported by: jhb > > diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c > index 93bdd41d1515..c4f5e586b0ed 100644 > --- a/sys/kern/kern_descrip.c > +++ b/sys/kern/kern_descrip.c > @@ -557,8 +557,10 @@ open_to_fde_flags(int open_flags, bool sticky_orb) > { .f = O_CLOFORK, .t = UF_FOCLOSE }, > { .f = O_RESOLVE_BENEATH, .t = UF_RESOLVE_BENEATH }, > }; > +#ifdef __clang__ > _Static_assert(open_to_fde_flags_s[nitems(open_to_fde_flags_s) - 1].f == > O_RESOLVE_BENEATH, "O_RESOLVE_BENEATH must be last, for sticky_orb"); > +#endif I think this is fine. Mark Millard followed up with me offline and it may be that GCC is technically more correct here with what is allowed to be computed as a static constant at compile time FWIW. C++' constexpr allows for a wider range of compile-time constant values compared to C and this sort of thing feels very constexpr-like. -- John Baldwin
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