From 6e7a315eb67cb6c113cf37e1d66c4f11a51a2b3e Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 18:29:51 +0200 Subject: Adding upstream version 2.06. Signed-off-by: Daniel Baumann --- m4/memchr.m4 | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 m4/memchr.m4 (limited to 'm4/memchr.m4') diff --git a/m4/memchr.m4 b/m4/memchr.m4 new file mode 100644 index 0000000..db227e7 --- /dev/null +++ b/m4/memchr.m4 @@ -0,0 +1,99 @@ +# memchr.m4 serial 13 +dnl Copyright (C) 2002-2004, 2009-2019 Free Software Foundation, Inc. +dnl This file is free software; the Free Software Foundation +dnl gives unlimited permission to copy and/or distribute it, +dnl with or without modifications, as long as this notice is preserved. + +AC_DEFUN_ONCE([gl_FUNC_MEMCHR], +[ + AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles + + dnl Check for prerequisites for memory fence checks. + gl_FUNC_MMAP_ANON + AC_CHECK_HEADERS_ONCE([sys/mman.h]) + AC_CHECK_FUNCS_ONCE([mprotect]) + + AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS]) + m4_ifdef([gl_FUNC_MEMCHR_OBSOLETE], [ + dnl These days, we assume memchr is present. But if support for old + dnl platforms is desired: + AC_CHECK_FUNCS_ONCE([memchr]) + if test $ac_cv_func_memchr = no; then + HAVE_MEMCHR=0 + fi + ]) + if test $HAVE_MEMCHR = 1; then + # Detect platform-specific bugs in some versions of glibc: + # memchr should not dereference anything with length 0 + # https://bugzilla.redhat.com/show_bug.cgi?id=499689 + # memchr should not dereference overestimated length after a match + # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737 + # https://sourceware.org/bugzilla/show_bug.cgi?id=10162 + # Assume that memchr works on platforms that lack mprotect. + AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works], + [AC_RUN_IFELSE([AC_LANG_PROGRAM([[ +#include +#if HAVE_SYS_MMAN_H +# include +# include +# include +# include +# ifndef MAP_FILE +# define MAP_FILE 0 +# endif +#endif +]], [[ + int result = 0; + char *fence = NULL; +#if HAVE_SYS_MMAN_H && HAVE_MPROTECT +# if HAVE_MAP_ANONYMOUS + const int flags = MAP_ANONYMOUS | MAP_PRIVATE; + const int fd = -1; +# else /* !HAVE_MAP_ANONYMOUS */ + const int flags = MAP_FILE | MAP_PRIVATE; + int fd = open ("/dev/zero", O_RDONLY, 0666); + if (fd >= 0) +# endif + { + int pagesize = getpagesize (); + char *two_pages = + (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE, + flags, fd, 0); + if (two_pages != (char *)(-1) + && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0) + fence = two_pages + pagesize; + } +#endif + if (fence) + { + if (memchr (fence, 0, 0)) + result |= 1; + strcpy (fence - 9, "12345678"); + if (memchr (fence - 9, 0, 79) != fence - 1) + result |= 2; + if (memchr (fence - 1, 0, 3) != fence - 1) + result |= 4; + } + return result; +]])], + [gl_cv_func_memchr_works=yes], + [gl_cv_func_memchr_works=no], + [case "$host_os" in + # Guess yes on native Windows. + mingw*) gl_cv_func_memchr_works="guessing yes" ;; + # Be pessimistic for now. + *) gl_cv_func_memchr_works="guessing no" ;; + esac + ]) + ]) + case "$gl_cv_func_memchr_works" in + *yes) ;; + *) REPLACE_MEMCHR=1 ;; + esac + fi +]) + +# Prerequisites of lib/memchr.c. +AC_DEFUN([gl_PREREQ_MEMCHR], [ + AC_CHECK_HEADERS([bp-sym.h]) +]) -- cgit v1.2.3