2 dnl Copyright (C) 2008 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 dnl Check that strstr is efficient.
8 AC_DEFUN([gl_FUNC_STRSTR],
10 AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
11 AC_CACHE_CHECK([whether strstr works in linear time],
12 [gl_cv_func_strstr_linear],
13 [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
14 #include <signal.h> /* for signal */
15 #include <string.h> /* for memmem */
16 #include <stdlib.h> /* for malloc */
17 #include <unistd.h> /* for alarm */
18 ]], [[size_t m = 1000000;
19 char *haystack = (char *) malloc (2 * m + 2);
20 char *needle = (char *) malloc (m + 2);
22 /* Failure to compile this test due to missing alarm is okay,
23 since all such platforms (mingw) also have quadratic strstr. */
24 signal (SIGALRM, SIG_DFL);
26 /* Check for quadratic performance. */
27 if (haystack && needle)
29 memset (haystack, 'A', 2 * m);
30 haystack[2 * m] = 'B';
31 haystack[2 * m + 1] = 0;
32 memset (needle, 'A', m);
35 result = strstr (haystack, needle);
38 [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
39 [dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
40 dnl strstr that works in linear time.
41 AC_EGREP_CPP([Lucky user],
44 #ifdef __GNU_LIBRARY__
45 #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)
50 #include <cygwin/version.h>
51 #if CYGWIN_VERSION_DLL_MAJOR >= 1007
56 [gl_cv_func_strstr_linear=yes],
57 [gl_cv_func_strstr_linear="guessing no"])
60 if test "$gl_cv_func_strstr_linear" != yes; then