2 dnl Copyright (C) 2002, 2003, 2004, 2007, 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 AC_DEFUN([gl_FUNC_MEMMEM],
9 dnl Persuade glibc <string.h> to declare memmem().
10 AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
12 AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
13 AC_REPLACE_FUNCS(memmem)
14 AC_CHECK_DECLS_ONCE(memmem)
15 if test $ac_cv_have_decl_memmem = no; then
18 AC_CACHE_CHECK([whether memmem works in linear time],
19 [gl_cv_func_memmem_works],
20 [AC_RUN_IFELSE([AC_LANG_PROGRAM([
21 #include <string.h> /* for memmem */
22 #include <stdlib.h> /* for malloc */
23 #include <unistd.h> /* for alarm */
24 ], [[size_t m = 1000000;
25 char *haystack = (char *) malloc (2 * m + 1);
26 char *needle = (char *) malloc (m + 1);
28 /* Failure to compile this test due to missing alarm is okay,
29 since all such platforms (mingw) also lack memmem. */
31 if (haystack && needle)
33 memset (haystack, 'A', 2 * m);
34 haystack[2 * m] = 'B';
35 memset (needle, 'A', m);
37 result = memmem (haystack, 2 * m + 1, needle, m + 1);
39 return !result || !memmem ("a", 1, 0, 0);]])],
40 [gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
41 [dnl pessimistically assume the worst, since even glibc 2.6.1
42 dnl has quadratic complexity in its memmem
43 gl_cv_func_memmem_works=no])])
44 if test $gl_cv_func_memmem_works = no; then
52 # Prerequisites of lib/memmem.c.
53 AC_DEFUN([gl_PREREQ_MEMMEM], [:])