Date: Thu, 19 Jan 2023 23:11:13 +0000 From: Jessica Clarke <jrtc27@freebsd.org> To: John Baldwin <jhb@FreeBSD.org> Cc: "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: 43703bc489ec - main - stdlib.h: Fix qsort_r compatibility with GCC 12. Message-ID: <F42A1D72-387E-4F3F-8C27-C95C5A244E1D@freebsd.org> In-Reply-To: <202301192249.30JMnCXf040410@gitrepo.freebsd.org> References: <202301192249.30JMnCXf040410@gitrepo.freebsd.org>
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On 19 Jan 2023, at 22:49, John Baldwin <jhb@FreeBSD.org> wrote: >=20 > The branch main has been updated by jhb: >=20 > URL: = https://cgit.FreeBSD.org/src/commit/?id=3D43703bc489ec504b947b869045c492ed= 38c1a69c >=20 > commit 43703bc489ec504b947b869045c492ed38c1a69c > Author: John Baldwin <jhb@FreeBSD.org> > AuthorDate: 2023-01-19 22:48:52 +0000 > Commit: John Baldwin <jhb@FreeBSD.org> > CommitDate: 2023-01-19 22:48:52 +0000 >=20 > stdlib.h: Fix qsort_r compatibility with GCC 12. >=20 > GCC 12 (unlike GCC 9) does not match a function argument passed to = the > old qsort_r() API (as is used in the qsort_r_compat test) to a > function pointer type via __generic. It treats the function type = as a > distinct type from a function pointer. As a workaround, add a = second > definition of qsort_r for GCC 12 which uses the bare function type. As far as I can tell both versions of GCC behave the same. The difference is whether __generic is using _Generic or __builtin_choose_expr with __builtin_types_compatible_p, since function and function pointer types are not compatible. Clang will take the __has_extension path, but GCC will take the builtins path, and so Clang works but GCC doesn=E2=80=99t. As a result of this change you=E2=80=99ve likely broken code that does qsort_r(..., &f) as that will have the opposite problem. The right fix is to force arg5 to decay, such as by (ab)using the comma operator with __generic((0, arg5), ...). I guess that probably belongs in the fallback implementation of __generic though, not here, which would give the following real fix: diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h index 83ba7584e5b9..f7eff4768151 100644 --- a/sys/sys/cdefs.h +++ b/sys/sys/cdefs.h @@ -312,6 +312,9 @@ * __generic(). Unlike _Generic(), this macro can only distinguish * between a single type, so it requires nested invocations to * distinguish multiple cases. + * + * Note that the comma operator is used to force expr to decay in order = to + * match _Generic. */ =20 #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >=3D 201112L) || \ @@ -321,7 +324,7 @@ #elif __GNUC_PREREQ__(3, 1) && !defined(__cplusplus) #define __generic(expr, t, yes, no) = \ __builtin_choose_expr( = \ - __builtin_types_compatible_p(__typeof(expr), t), yes, no) + __builtin_types_compatible_p(__typeof((0, expr)), t), yes, = no) #endif =20 /* Does that work instead for you after reverting this commit? Jess > Reviewed by: emaste > Differential Revision: https://reviews.freebsd.org/D37410 > --- > include/stdlib.h | 6 ++++++ > 1 file changed, 6 insertions(+) >=20 > diff --git a/include/stdlib.h b/include/stdlib.h > index 754e8f5f5fd4..30d24aea1c10 100644 > --- a/include/stdlib.h > +++ b/include/stdlib.h > @@ -352,9 +352,15 @@ void __qsort_r_compat(void *, size_t, size_t, = void *, > __sym_compat(qsort_r, __qsort_r_compat, FBSD_1.0); > #endif > #if defined(__generic) && !defined(__cplusplus) > +#if __GNUC__ =3D=3D 12 > +#define qsort_r(base, nel, width, arg4, arg5) = \ > + __generic(arg5, int (void *, const void *, const void *), = \ > + __qsort_r_compat, qsort_r)(base, nel, width, arg4, arg5) > +#else > #define qsort_r(base, nel, width, arg4, arg5) = \ > __generic(arg5, int (*)(void *, const void *, const void *), = \ > __qsort_r_compat, qsort_r)(base, nel, width, arg4, arg5) > +#endif > #elif defined(__cplusplus) > __END_DECLS > extern "C++" {
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