X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Fmemmem.m4;h=98bb49122706862d51bc9fde7fd623ed5e0b105e;hb=95886da0b417a14882bb47bf4765f7af450d51da;hp=a529af3bec07664bba717345496135b596c11291;hpb=fc068cf4eb6814e848e4dc54e1c5cf4c30a79a6f;p=gnulib.git

diff --git a/m4/memmem.m4 b/m4/memmem.m4
index a529af3be..98bb49122 100644
--- a/m4/memmem.m4
+++ b/m4/memmem.m4
@@ -1,34 +1,151 @@
-# memmem.m4 serial 6
-dnl Copyright (C) 2002, 2003, 2004, 2007 Free Software Foundation, Inc.
+# memmem.m4 serial 24
+dnl Copyright (C) 2002-2004, 2007-2014 Free Software 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 and functional.
+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_CHECK_FUNCS([memmem])
+  if test $ac_cv_func_memmem = yes; then
+    HAVE_MEMMEM=1
+  else
+    HAVE_MEMMEM=0
+  fi
+  AC_CHECK_DECLS_ONCE([memmem])
   if test $ac_cv_have_decl_memmem = no; then
     HAVE_DECL_MEMMEM=0
   else
-    AC_CACHE_CHECK([whether memmem works], [gl_cv_func_memmem_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <string.h>],
-	  [return !memmem ("a", 1, NULL, 0);])],
-	[gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
-	[dnl pessimistically assume the worst, since even glibc 2.6.1
-	 dnl has quadratic complexity in its memmem
-	 gl_cv_func_memmem_works=no])])
-    if test $gl_cv_func_memmem_works = no; then
-      REPLACE_MEMMEM=1
-      AC_LIBOBJ([memmem])
-    fi
+    dnl Detect http://sourceware.org/bugzilla/show_bug.cgi?id=12092.
+    dnl Also check that we handle empty needles correctly.
+    AC_CACHE_CHECK([whether memmem works],
+      [gl_cv_func_memmem_works_always],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <string.h> /* for memmem */
+#define P "_EF_BF_BD"
+#define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P
+#define NEEDLE P P P P P
+]], [[
+    int result = 0;
+    if (memmem (HAYSTACK, strlen (HAYSTACK), NEEDLE, strlen (NEEDLE)))
+      result |= 1;
+    /* Check for empty needle behavior.  */
+    {
+      const char *haystack = "AAA";
+      if (memmem (haystack, 3, NULL, 0) != haystack)
+        result |= 2;
+    }
+    return result;
+    ]])],
+        [gl_cv_func_memmem_works_always=yes],
+        [gl_cv_func_memmem_works_always=no],
+        [dnl glibc 2.9..2.12 and cygwin 1.7.7 have issue #12092 above.
+         dnl Also empty needles work on glibc >= 2.1 and cygwin >= 1.7.0.
+         dnl uClibc is not affected, since it uses different source code.
+         dnl Assume that it works on all other platforms (even if not linear).
+         AC_EGREP_CPP([Lucky user],
+           [
+#ifdef __GNU_LIBRARY__
+ #include <features.h>
+ #if ((__GLIBC__ == 2 && ((__GLIBC_MINOR > 0 && __GLIBC_MINOR__ < 9) \
+                          || __GLIBC_MINOR__ > 12)) \
+      || (__GLIBC__ > 2)) \
+     || defined __UCLIBC__
+  Lucky user
+ #endif
+#elif defined __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
+  Lucky user
+ #endif
+#else
+  Lucky user
+#endif
+           ],
+           [gl_cv_func_memmem_works_always="guessing yes"],
+           [gl_cv_func_memmem_works_always="guessing no"])
+        ])
+      ])
+    case "$gl_cv_func_memmem_works_always" in
+      *yes) ;;
+      *)
+        REPLACE_MEMMEM=1
+        ;;
+    esac
   fi
   gl_PREREQ_MEMMEM
-])
+]) # gl_FUNC_MEMMEM_SIMPLE
+
+dnl Additionally, check that memmem has linear performance characteristics
+AC_DEFUN([gl_FUNC_MEMMEM],
+[
+  AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE])
+  if test $HAVE_DECL_MEMMEM = 1 && test $REPLACE_MEMMEM = 0; then
+    AC_CACHE_CHECK([whether memmem works in linear time],
+      [gl_cv_func_memmem_works_fast],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
+#include <string.h> /* for memmem */
+#include <stdlib.h> /* for malloc */
+#include <unistd.h> /* for alarm */
+static void quit (int sig) { exit (sig + 128); }
+]], [[
+    int result = 0;
+    size_t m = 1000000;
+    char *haystack = (char *) malloc (2 * m + 1);
+    char *needle = (char *) malloc (m + 1);
+    /* Failure to compile this test due to missing alarm is okay,
+       since all such platforms (mingw) also lack memmem.  */
+    signal (SIGALRM, quit);
+    alarm (5);
+    /* Check for quadratic performance.  */
+    if (haystack && needle)
+      {
+        memset (haystack, 'A', 2 * m);
+        haystack[2 * m] = 'B';
+        memset (needle, 'A', m);
+        needle[m] = 'B';
+        if (!memmem (haystack, 2 * m + 1, needle, m + 1))
+          result |= 1;
+      }
+    return result;
+    ]])],
+        [gl_cv_func_memmem_works_fast=yes], [gl_cv_func_memmem_works_fast=no],
+        [dnl Only glibc >= 2.9 and cygwin > 1.7.0 are known to have a
+         dnl memmem that works in linear time.
+         AC_EGREP_CPP([Lucky user],
+           [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)) \
+     && !defined __UCLIBC__
+  Lucky user
+ #endif
+#endif
+#ifdef __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 0)
+  Lucky user
+ #endif
+#endif
+           ],
+           [gl_cv_func_memmem_works_fast="guessing yes"],
+           [gl_cv_func_memmem_works_fast="guessing no"])
+        ])
+      ])
+    case "$gl_cv_func_memmem_works_fast" in
+      *yes) ;;
+      *)
+        REPLACE_MEMMEM=1
+        ;;
+    esac
+  fi
+]) # gl_FUNC_MEMMEM
 
 # Prerequisites of lib/memmem.c.
 AC_DEFUN([gl_PREREQ_MEMMEM], [:])