2 dnl Copyright (C) 2002-2004, 2007-2011 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 memmem is present and functional.
8 AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
10 dnl Persuade glibc <string.h> to declare memmem().
11 AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
13 AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
14 AC_REPLACE_FUNCS([memmem])
15 AC_CHECK_DECLS_ONCE([memmem])
16 if test $ac_cv_have_decl_memmem = no; then
19 dnl Detect http://sourceware.org/bugzilla/show_bug.cgi?id=12092.
20 dnl Also check that we handle empty needles correctly.
21 AC_CACHE_CHECK([whether memmem works],
22 [gl_cv_func_memmem_works_always],
23 [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
24 #include <string.h> /* for memmem */
26 #define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P
27 #define NEEDLE P P P P P
30 if (memmem (HAYSTACK, strlen (HAYSTACK), NEEDLE, strlen (NEEDLE)))
32 /* Check for empty needle behavior. */
34 const char *haystack = "AAA";
35 if (memmem (haystack, 3, NULL, 0) != haystack)
40 [gl_cv_func_memmem_works_always=yes],
41 [gl_cv_func_memmem_works_always=no],
42 [dnl glibc 2.9..2.12 and cygwin 1.7.7 have issue #12092 above.
43 dnl Also empty needles work on glibc >= 2.1 and cygwin >= 1.7.0.
44 dnl uClibc is not affected, since it uses different source code.
45 dnl Assume that it works on all other platforms (even if not linear).
46 AC_EGREP_CPP([Lucky user],
48 #ifdef __GNU_LIBRARY__
50 #if ((__GLIBC__ == 2 && ((__GLIBC_MINOR > 0 && __GLIBC_MINOR__ < 9) \
51 || __GLIBC_MINOR__ > 12)) \
56 #elif defined __CYGWIN__
57 #include <cygwin/version.h>
58 #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
65 [gl_cv_func_memmem_works_always=yes],
66 [gl_cv_func_memmem_works_always="guessing no"])
69 if test "$gl_cv_func_memmem_works_always" != yes; then
75 ]) # gl_FUNC_MEMMEM_SIMPLE
77 dnl Additionally, check that memmem has linear performance characteristics
78 AC_DEFUN([gl_FUNC_MEMMEM],
80 AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE])
81 if test $HAVE_DECL_MEMMEM = 1 && test $REPLACE_MEMMEM = 0; then
82 AC_CACHE_CHECK([whether memmem works in linear time],
83 [gl_cv_func_memmem_works_fast],
84 [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
85 #include <signal.h> /* for signal */
86 #include <string.h> /* for memmem */
87 #include <stdlib.h> /* for malloc */
88 #include <unistd.h> /* for alarm */
89 static void quit (int sig) { exit (sig + 128); }
93 char *haystack = (char *) malloc (2 * m + 1);
94 char *needle = (char *) malloc (m + 1);
95 /* Failure to compile this test due to missing alarm is okay,
96 since all such platforms (mingw) also lack memmem. */
97 signal (SIGALRM, quit);
99 /* Check for quadratic performance. */
100 if (haystack && needle)
102 memset (haystack, 'A', 2 * m);
103 haystack[2 * m] = 'B';
104 memset (needle, 'A', m);
106 if (!memmem (haystack, 2 * m + 1, needle, m + 1))
111 [gl_cv_func_memmem_works_fast=yes], [gl_cv_func_memmem_works_fast=no],
112 [dnl Only glibc >= 2.9 and cygwin > 1.7.0 are known to have a
113 dnl memmem that works in linear time.
114 AC_EGREP_CPP([Lucky user],
116 #include <features.h>
117 #ifdef __GNU_LIBRARY__
118 #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)) \
119 && !defined __UCLIBC__
124 #include <cygwin/version.h>
125 #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 0)
130 [gl_cv_func_memmem_works_fast=yes],
131 [gl_cv_func_memmem_works_fast="guessing no"])
134 if test "$gl_cv_func_memmem_works_fast" != yes; then
141 # Prerequisites of lib/memmem.c.
142 AC_DEFUN([gl_PREREQ_MEMMEM], [:])