gnulib/import/m4/strstr.m4

   1 # strstr.m4 serial 17
   2 dnl Copyright (C) 2008-2016 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.
   6
   7 dnl Check that strstr works.
   8 AC_DEFUN([gl_FUNC_STRSTR_SIMPLE],
   9 [
  10   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
  11   AC_REQUIRE([gl_FUNC_MEMCHR])
  12   if test "$gl_cv_func_memchr_works" != yes; then
  13     REPLACE_STRSTR=1
  14   else
  15     dnl Detect http://sourceware.org/bugzilla/show_bug.cgi?id=12092.
  16     AC_CACHE_CHECK([whether strstr works],
  17       [gl_cv_func_strstr_works_always],
  18       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
  19 #include <string.h> /* for strstr */
  20 #define P "_EF_BF_BD"
  21 #define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P
  22 #define NEEDLE P P P P P
  23 ]], [[return !!strstr (HAYSTACK, NEEDLE);
  24     ]])],
  25         [gl_cv_func_strstr_works_always=yes],
  26         [gl_cv_func_strstr_works_always=no],
  27         [dnl glibc 2.12 and cygwin 1.7.7 have a known bug.  uClibc is not
  28          dnl affected, since it uses different source code for strstr than
  29          dnl glibc.
  30          dnl Assume that it works on all other platforms, even if it is not
  31          dnl linear.
  32          AC_EGREP_CPP([Lucky user],
  33            [
  34 #ifdef __GNU_LIBRARY__
  35  #include <features.h>
  36  #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
  37      || defined __UCLIBC__
  38   Lucky user
  39  #endif
  40 #elif defined __CYGWIN__
  41  #include <cygwin/version.h>
  42  #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
  43   Lucky user
  44  #endif
  45 #else
  46   Lucky user
  47 #endif
  48            ],
  49            [gl_cv_func_strstr_works_always="guessing yes"],
  50            [gl_cv_func_strstr_works_always="guessing no"])
  51         ])
  52       ])
  53     case "$gl_cv_func_strstr_works_always" in
  54       *yes) ;;
  55       *)
  56         REPLACE_STRSTR=1
  57         ;;
  58     esac
  59   fi
  60 ]) # gl_FUNC_STRSTR_SIMPLE
  61
  62 dnl Additionally, check that strstr is efficient.
  63 AC_DEFUN([gl_FUNC_STRSTR],
  64 [
  65   AC_REQUIRE([gl_FUNC_STRSTR_SIMPLE])
  66   if test $REPLACE_STRSTR = 0; then
  67     AC_CACHE_CHECK([whether strstr works in linear time],
  68       [gl_cv_func_strstr_linear],
  69       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
  70 #ifdef __MVS__
  71 /* z/OS does not deliver signals while strstr() is running (thanks to
  72    restrictions on its LE runtime), which prevents us from limiting the
  73    running time of this test.  */
  74 # error "This test does not work properly on z/OS"
  75 #endif
  76 #include <signal.h> /* for signal */
  77 #include <string.h> /* for strstr */
  78 #include <stdlib.h> /* for malloc */
  79 #include <unistd.h> /* for alarm */
  80 static void quit (int sig) { _exit (sig + 128); }
  81 ]], [[
  82     int result = 0;
  83     size_t m = 1000000;
  84     char *haystack = (char *) malloc (2 * m + 2);
  85     char *needle = (char *) malloc (m + 2);
  86     /* Failure to compile this test due to missing alarm is okay,
  87        since all such platforms (mingw) also have quadratic strstr.  */
  88     signal (SIGALRM, quit);
  89     alarm (5);
  90     /* Check for quadratic performance.  */
  91     if (haystack && needle)
  92       {
  93         memset (haystack, 'A', 2 * m);
  94         haystack[2 * m] = 'B';
  95         haystack[2 * m + 1] = 0;
  96         memset (needle, 'A', m);
  97         needle[m] = 'B';
  98         needle[m + 1] = 0;
  99         if (!strstr (haystack, needle))
 100           result |= 1;
 101       }
 102     return result;
 103     ]])],
 104         [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
 105         [dnl Only glibc > 2.12 on processors without SSE 4.2 instructions and
 106          dnl cygwin > 1.7.7 are known to have a bug-free strstr that works in
 107          dnl linear time.
 108          AC_EGREP_CPP([Lucky user],
 109            [
 110 #include <features.h>
 111 #ifdef __GNU_LIBRARY__
 112  #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
 113      && !(defined __i386__ || defined __x86_64__) \
 114      && !defined __UCLIBC__
 115   Lucky user
 116  #endif
 117 #endif
 118 #ifdef __CYGWIN__
 119  #include <cygwin/version.h>
 120  #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
 121   Lucky user
 122  #endif
 123 #endif
 124            ],
 125            [gl_cv_func_strstr_linear="guessing yes"],
 126            [gl_cv_func_strstr_linear="guessing no"])
 127         ])
 128       ])
 129     case "$gl_cv_func_strstr_linear" in
 130       *yes) ;;
 131       *)
 132         REPLACE_STRSTR=1
 133         ;;
 134     esac
 135   fi
 136 ]) # gl_FUNC_STRSTR