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# strstr.m4 serial 4
dnl Copyright (C) 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,
dnl with or without modifications, as long as this notice is preserved.
dnl Check that strstr is efficient.
AC_DEFUN([gl_FUNC_STRSTR],
[
AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
AC_CACHE_CHECK([whether strstr works in linear time],
[gl_cv_func_strstr_linear],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <string.h> /* for memmem */
#include <stdlib.h> /* for malloc */
#include <unistd.h> /* for alarm */
]], [[size_t m = 1000000;
char *haystack = (char *) malloc (2 * m + 2);
char *needle = (char *) malloc (m + 2);
void *result = 0;
/* Failure to compile this test due to missing alarm is okay,
since all such platforms (mingw) also have quadratic strstr. */
alarm (5);
/* Check for quadratic performance. */
if (haystack && needle)
{
memset (haystack, 'A', 2 * m);
haystack[2 * m] = 'B';
haystack[2 * m + 1] = 0;
memset (needle, 'A', m);
needle[m] = 'B';
needle[m + 1] = 0;
result = strstr (haystack, needle);
}
return !result;]])],
[gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
[dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
dnl strstr 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_strstr_linear=yes],
[gl_cv_func_strstr_linear="guessing no"])
])
])
if test "$gl_cv_func_strstr_linear" != yes; then
REPLACE_STRSTR=1
AC_LIBOBJ([strstr])
fi
]) # gl_FUNC_STRSTR
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