gnulib/import/m4/strstr.m4

   1 # strstr.m4 serial 21
   2 dnl Copyright (C) 2008-2019 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 $HAVE_MEMCHR = 0 || test $REPLACE_MEMCHR = 1; then
  13     REPLACE_STRSTR=1
  14   else
  15     dnl Detect https://sourceware.org/bugzilla/show_bug.cgi?id=12092
  16     dnl and https://sourceware.org/bugzilla/show_bug.cgi?id=23637.
  17     AC_CACHE_CHECK([whether strstr works],
  18       [gl_cv_func_strstr_works_always],
  19       [AC_RUN_IFELSE(
  20          [AC_LANG_PROGRAM([[
  21 #include <string.h> /* for strstr */
  22 #ifdef __GNU_LIBRARY__
  23  #include <features.h>
  24  #if __GLIBC__ == 2 && __GLIBC_MINOR__ == 28
  25   Unlucky user
  26  #endif
  27 #endif
  28 #define P "_EF_BF_BD"
  29 #define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P
  30 #define NEEDLE P P P P P
  31 ]],
  32             [[return !!strstr (HAYSTACK, NEEDLE);
  33             ]])],
  34          [gl_cv_func_strstr_works_always=yes],
  35          [gl_cv_func_strstr_works_always=no],
  36          [dnl glibc 2.12 and cygwin 1.7.7 have a known bug.  uClibc is not
  37           dnl affected, since it uses different source code for strstr than
  38           dnl glibc.
  39           dnl Assume that it works on all other platforms, even if it is not
  40           dnl linear.
  41           AC_EGREP_CPP([Lucky user],
  42             [
  43 #ifdef __GNU_LIBRARY__
  44  #include <features.h>
  45  #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
  46      || defined __UCLIBC__
  47   Lucky user
  48  #endif
  49 #elif defined __CYGWIN__
  50  #include <cygwin/version.h>
  51  #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
  52   Lucky user
  53  #endif
  54 #else
  55   Lucky user
  56 #endif
  57             ],
  58             [gl_cv_func_strstr_works_always="guessing yes"],
  59             [gl_cv_func_strstr_works_always="$gl_cross_guess_normal"])
  60          ])
  61       ])
  62     case "$gl_cv_func_strstr_works_always" in
  63       *yes) ;;
  64       *)
  65         REPLACE_STRSTR=1
  66         ;;
  67     esac
  68   fi
  69 ]) # gl_FUNC_STRSTR_SIMPLE
  70
  71 dnl Additionally, check that strstr is efficient.
  72 AC_DEFUN([gl_FUNC_STRSTR],
  73 [
  74   AC_REQUIRE([gl_FUNC_STRSTR_SIMPLE])
  75   if test $REPLACE_STRSTR = 0; then
  76     AC_CACHE_CHECK([whether strstr works in linear time],
  77       [gl_cv_func_strstr_linear],
  78       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
  79 #ifdef __MVS__
  80 /* z/OS does not deliver signals while strstr() is running (thanks to
  81    restrictions on its LE runtime), which prevents us from limiting the
  82    running time of this test.  */
  83 # error "This test does not work properly on z/OS"
  84 #endif
  85 #include <signal.h> /* for signal */
  86 #include <string.h> /* for strstr */
  87 #include <stdlib.h> /* for malloc */
  88 #include <unistd.h> /* for alarm */
  89 static void quit (int sig) { _exit (sig + 128); }
  90 ]], [[
  91     int result = 0;
  92     size_t m = 1000000;
  93     char *haystack = (char *) malloc (2 * m + 2);
  94     char *needle = (char *) malloc (m + 2);
  95     /* Failure to compile this test due to missing alarm is okay,
  96        since all such platforms (mingw) also have quadratic strstr.  */
  97     signal (SIGALRM, quit);
  98     alarm (5);
  99     /* Check for quadratic performance.  */
 100     if (haystack && needle)
 101       {
 102         memset (haystack, 'A', 2 * m);
 103         haystack[2 * m] = 'B';
 104         haystack[2 * m + 1] = 0;
 105         memset (needle, 'A', m);
 106         needle[m] = 'B';
 107         needle[m + 1] = 0;
 108         if (!strstr (haystack, needle))
 109           result |= 1;
 110       }
 111     /* Free allocated memory, in case some sanitizer is watching.  */
 112     free (haystack);
 113     free (needle);
 114     return result;
 115     ]])],
 116         [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
 117         [dnl Only glibc > 2.12 on processors without SSE 4.2 instructions and
 118          dnl cygwin > 1.7.7 are known to have a bug-free strstr that works in
 119          dnl linear time.
 120          AC_EGREP_CPP([Lucky user],
 121            [
 122 #include <features.h>
 123 #ifdef __GNU_LIBRARY__
 124  #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
 125      && !(defined __i386__ || defined __x86_64__) \
 126      && !defined __UCLIBC__
 127   Lucky user
 128  #endif
 129 #endif
 130 #ifdef __CYGWIN__
 131  #include <cygwin/version.h>
 132  #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
 133   Lucky user
 134  #endif
 135 #endif
 136            ],
 137            [gl_cv_func_strstr_linear="guessing yes"],
 138            [gl_cv_func_strstr_linear="$gl_cross_guess_normal"])
 139         ])
 140       ])
 141     case "$gl_cv_func_strstr_linear" in
 142       *yes) ;;
 143       *)
 144         REPLACE_STRSTR=1
 145         ;;
 146     esac
 147   fi
 148 ]) # gl_FUNC_STRSTR