Commit | Line | Data |
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f6ea5628 | 1 | # memmem.m4 serial 9 |
0fb0cc75 JB |
2 | dnl Copyright (C) 2002, 2003, 2004, 2007, 2008, 2009 |
3 | Free Software Foundation, Inc. | |
f6ea5628 DJ |
4 | dnl This file is free software; the Free Software Foundation |
5 | dnl gives unlimited permission to copy and/or distribute it, | |
6 | dnl with or without modifications, as long as this notice is preserved. | |
7 | ||
8 | dnl Check that memmem is present. | |
9 | AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE], | |
10 | [ | |
11 | dnl Persuade glibc <string.h> to declare memmem(). | |
12 | AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) | |
13 | ||
14 | AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS]) | |
15 | AC_REPLACE_FUNCS(memmem) | |
16 | AC_CHECK_DECLS_ONCE(memmem) | |
17 | if test $ac_cv_have_decl_memmem = no; then | |
18 | HAVE_DECL_MEMMEM=0 | |
19 | fi | |
20 | gl_PREREQ_MEMMEM | |
21 | ]) # gl_FUNC_MEMMEM_SIMPLE | |
22 | ||
23 | dnl Additionally, check that memmem is efficient and handles empty needles. | |
24 | AC_DEFUN([gl_FUNC_MEMMEM], | |
25 | [ | |
26 | AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE]) | |
27 | if test $ac_cv_have_decl_memmem = yes; then | |
28 | AC_CACHE_CHECK([whether memmem works in linear time], | |
29 | [gl_cv_func_memmem_works], | |
30 | [AC_RUN_IFELSE([AC_LANG_PROGRAM([ | |
31 | #include <string.h> /* for memmem */ | |
32 | #include <stdlib.h> /* for malloc */ | |
33 | #include <unistd.h> /* for alarm */ | |
34 | ], [[size_t m = 1000000; | |
35 | char *haystack = (char *) malloc (2 * m + 1); | |
36 | char *needle = (char *) malloc (m + 1); | |
37 | void *result = 0; | |
38 | /* Failure to compile this test due to missing alarm is okay, | |
39 | since all such platforms (mingw) also lack memmem. */ | |
40 | alarm (5); | |
41 | /* Check for quadratic performance. */ | |
42 | if (haystack && needle) | |
43 | { | |
44 | memset (haystack, 'A', 2 * m); | |
45 | haystack[2 * m] = 'B'; | |
46 | memset (needle, 'A', m); | |
47 | needle[m] = 'B'; | |
48 | result = memmem (haystack, 2 * m + 1, needle, m + 1); | |
49 | } | |
50 | /* Check for empty needle behavior. */ | |
51 | return !result || !memmem ("a", 1, 0, 0);]])], | |
52 | [gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no], | |
53 | [dnl pessimistically assume the worst, since even glibc 2.6.1 | |
54 | dnl has quadratic complexity in its memmem | |
55 | gl_cv_func_memmem_works="guessing no"])]) | |
56 | if test "$gl_cv_func_memmem_works" != yes; then | |
57 | REPLACE_MEMMEM=1 | |
58 | AC_LIBOBJ([memmem]) | |
59 | fi | |
60 | fi | |
61 | ]) # gl_FUNC_MEMMEM | |
62 | ||
63 | # Prerequisites of lib/memmem.c. | |
64 | AC_DEFUN([gl_PREREQ_MEMMEM], [:]) |