-# memmem.m4 serial 5
-dnl Copyright (C) 2002, 2003, 2004, 2007 Free Software Foundation, Inc.
+# memmem.m4 serial 14
+dnl Copyright (C) 2002, 2003, 2004, 2007, 2008, 2009, 2010 Free Software
+dnl 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.
-AC_DEFUN([gl_FUNC_MEMMEM],
+dnl Check that memmem is present.
+AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
[
dnl Persuade glibc <string.h> to declare memmem().
AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
- AC_REPLACE_FUNCS(memmem)
- AC_CHECK_DECLS_ONCE(memmem)
+ AC_REPLACE_FUNCS([memmem])
+ AC_CHECK_DECLS_ONCE([memmem])
if test $ac_cv_have_decl_memmem = no; then
HAVE_DECL_MEMMEM=0
fi
gl_PREREQ_MEMMEM
-])
+]) # gl_FUNC_MEMMEM_SIMPLE
+
+dnl Additionally, check that memmem is efficient and handles empty needles.
+AC_DEFUN([gl_FUNC_MEMMEM],
+[
+ AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE])
+ if test $ac_cv_have_decl_memmem = yes; then
+ AC_CACHE_CHECK([whether memmem works in linear time],
+ [gl_cv_func_memmem_works],
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
+#include <string.h> /* for memmem */
+#include <stdlib.h> /* for malloc */
+#include <unistd.h> /* for alarm */
+]], [[size_t m = 1000000;
+ char *haystack = (char *) malloc (2 * m + 1);
+ char *needle = (char *) malloc (m + 1);
+ void *result = 0;
+ /* Failure to compile this test due to missing alarm is okay,
+ since all such platforms (mingw) also lack memmem. */
+ signal (SIGALRM, SIG_DFL);
+ alarm (5);
+ /* Check for quadratic performance. */
+ if (haystack && needle)
+ {
+ memset (haystack, 'A', 2 * m);
+ haystack[2 * m] = 'B';
+ memset (needle, 'A', m);
+ needle[m] = 'B';
+ result = memmem (haystack, 2 * m + 1, needle, m + 1);
+ }
+ /* Check for empty needle behavior. */
+ return !result || !memmem ("a", 1, 0, 0);]])],
+ [gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
+ [dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
+ dnl memmem that works in linear time.
+ AC_EGREP_CPP([Lucky user],
+ [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)
+ Lucky user
+ #endif
+#endif
+#ifdef __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_MAJOR >= 1007
+ Lucky user
+ #endif
+#endif
+ ],
+ [gl_cv_func_memmem_works=yes],
+ [gl_cv_func_memmem_works="guessing no"])
+ ])
+ ])
+ if test "$gl_cv_func_memmem_works" != yes; then
+ REPLACE_MEMMEM=1
+ AC_LIBOBJ([memmem])
+ fi
+ fi
+]) # gl_FUNC_MEMMEM
# Prerequisites of lib/memmem.c.
AC_DEFUN([gl_PREREQ_MEMMEM], [:])