-# memmem.m4 serial 8
+# memmem.m4 serial 13
dnl Copyright (C) 2002, 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
if test $ac_cv_have_decl_memmem = yes; then
AC_CACHE_CHECK([whether memmem works in linear time],
[gl_cv_func_memmem_works],
- [AC_RUN_IFELSE([AC_LANG_PROGRAM([
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
#include <string.h> /* for memmem */
#include <stdlib.h> /* for malloc */
#include <unistd.h> /* for alarm */
-], [[size_t m = 1000000;
+]], [[size_t m = 1000000;
char *haystack = (char *) malloc (2 * m + 1);
char *needle = (char *) malloc (m + 1);
void *result = 0;
/* Failure to compile this test due to missing alarm is okay,
since all such platforms (mingw) also lack memmem. */
+ signal (SIGALRM, SIG_DFL);
alarm (5);
/* Check for quadratic performance. */
if (haystack && needle)
/* Check for empty needle behavior. */
return !result || !memmem ("a", 1, 0, 0);]])],
[gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
- [dnl pessimistically assume the worst, since even glibc 2.6.1
- dnl has quadratic complexity in its memmem
- gl_cv_func_memmem_works=no])])
- if test $gl_cv_func_memmem_works = no; then
+ [dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
+ dnl memmem that works in linear time.
+ AC_EGREP_CPP([Lucky user],
+ [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)
+ Lucky user
+ #endif
+#endif
+#ifdef __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_MAJOR >= 1007
+ Lucky user
+ #endif
+#endif
+ ],
+ [gl_cv_func_memmem_works=yes],
+ [gl_cv_func_memmem_works="guessing no"])
+ ])
+ ])
+ if test "$gl_cv_func_memmem_works" != yes; then
REPLACE_MEMMEM=1
AC_LIBOBJ([memmem])
fi