On 9/17/20 8:30 AM, Nelson H. F. Beebe wrote:
On OpenMandriva Lx 4.1 (Mercury), with /usr/bin/cc == clang version 9.0.1, I getCC dfa.o In file included from dfa.c:61: ./xalloc.h:94:7: error: use of unknown builtin '__builtin_mul_overflow_p' [-Wimplicit-function-declaration] if (xalloc_oversized (n, s)) ^ ./xalloc-oversized.h:46:4: note: expanded from macro 'xalloc_oversized' __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1) ^ ... long cascade of similar errors ...
Thanks for reporting that. I guess Clang 9.0.1 defines __GNUC__ to be >=7 even though it doesn't implement all GCC 7 features. I installed the attached patch into Gnulib to try to work around this glitch, and this patch should appear in Grep the next time it syncs with Gnulib. cc'ing to bug-gnulib.
>From 494aaa530b32b4290df9a31d123bf1825eda7217 Mon Sep 17 00:00:00 2001 From: Paul Eggert <egg...@cs.ucla.edu> Date: Thu, 17 Sep 2020 12:17:15 -0700 Subject: [PATCH] intprops, xalloc: avoid __builtin_mul_overflow_p with Clang Problem reported by Nelson H. F. Beebe for clang 9.0.1 in: https://lists.gnu.org/r/grep-devel/2020-09/msg00028.html * lib/intprops.h (_GL_HAS_BUILTIN_OVERFLOW_P) [__clang__]: Define to 0. * lib/xalloc-oversized.h (xalloc_oversized) [__clang__]: Do not use __builtin_mul_overflow_p. --- ChangeLog | 8 ++++++++ lib/intprops.h | 8 +++++++- lib/xalloc-oversized.h | 2 +- 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index b484c8dec..a3a8ab1e2 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,13 @@ 2020-09-17 Paul Eggert <egg...@cs.ucla.edu> + intprops, xalloc: avoid __builtin_mul_overflow_p with Clang + Problem reported by Nelson H. F. Beebe for clang 9.0.1 in: + https://lists.gnu.org/r/grep-devel/2020-09/msg00028.html + * lib/intprops.h (_GL_HAS_BUILTIN_OVERFLOW_P) [__clang__]: + Define to 0. + * lib/xalloc-oversized.h (xalloc_oversized) [__clang__]: + Do not use __builtin_mul_overflow_p. + libc-config: port __THROW to Ubuntu 4 * lib/cdefs.h (__THROW): Do not use __attribute__ ((__nothrow__)) for GCC 3.3. Problem reported by Jeffrey Walton in: diff --git a/lib/intprops.h b/lib/intprops.h index df66a3877..cb086715b 100644 --- a/lib/intprops.h +++ b/lib/intprops.h @@ -244,7 +244,13 @@ /* True if __builtin_add_overflow_p (A, B, C) works, and similarly for __builtin_sub_overflow_p and __builtin_mul_overflow_p. */ -#define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__) +#ifdef __clang__ +/* Clang 9 lacks __builtin_mul_overflow_p, and even if it did it would + presumably run afoul of Clang bug 16404. */ +# define _GL_HAS_BUILTIN_OVERFLOW_P 0 +#else +# define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__) +#endif /* The _GL*_OVERFLOW macros have the same restrictions as the *_RANGE_OVERFLOW macros, except that they do not assume that operands diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h index 13ee23031..7cd4a74f0 100644 --- a/lib/xalloc-oversized.h +++ b/lib/xalloc-oversized.h @@ -41,7 +41,7 @@ typedef size_t __xalloc_count_type; positive and N must be nonnegative. This is a macro, not a function, so that it works correctly even when SIZE_MAX < N. */ -#if 7 <= __GNUC__ +#if 7 <= __GNUC__ && !defined __clang__ # define xalloc_oversized(n, s) \ __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1) #elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ -- 2.17.1
