1# strstr.m4 serial 16
2dnl Copyright (C) 2008-2014 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7dnl Check that strstr works.
8AC_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
62dnl Additionally, check that strstr is efficient.
63AC_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#include <signal.h> /* for signal */
71#include <string.h> /* for strstr */
72#include <stdlib.h> /* for malloc */
73#include <unistd.h> /* for alarm */
74static void quit (int sig) { exit (sig + 128); }
75]], [[
76    int result = 0;
77    size_t m = 1000000;
78    char *haystack = (char *) malloc (2 * m + 2);
79    char *needle = (char *) malloc (m + 2);
80    /* Failure to compile this test due to missing alarm is okay,
81       since all such platforms (mingw) also have quadratic strstr.  */
82    signal (SIGALRM, quit);
83    alarm (5);
84    /* Check for quadratic performance.  */
85    if (haystack && needle)
86      {
87        memset (haystack, 'A', 2 * m);
88        haystack[2 * m] = 'B';
89        haystack[2 * m + 1] = 0;
90        memset (needle, 'A', m);
91        needle[m] = 'B';
92        needle[m + 1] = 0;
93        if (!strstr (haystack, needle))
94          result |= 1;
95      }
96    return result;
97    ]])],
98        [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
99        [dnl Only glibc > 2.12 on processors without SSE 4.2 instructions and
100         dnl cygwin > 1.7.7 are known to have a bug-free strstr that works in
101         dnl linear time.
102         AC_EGREP_CPP([Lucky user],
103           [
104#include <features.h>
105#ifdef __GNU_LIBRARY__
106 #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ > 12) || (__GLIBC__ > 2)) \
107     && !(defined __i386__ || defined __x86_64__) \
108     && !defined __UCLIBC__
109  Lucky user
110 #endif
111#endif
112#ifdef __CYGWIN__
113 #include <cygwin/version.h>
114 #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7)
115  Lucky user
116 #endif
117#endif
118           ],
119           [gl_cv_func_strstr_linear="guessing yes"],
120           [gl_cv_func_strstr_linear="guessing no"])
121        ])
122      ])
123    case "$gl_cv_func_strstr_linear" in
124      *yes) ;;
125      *)
126        REPLACE_STRSTR=1
127        ;;
128    esac
129  fi
130]) # gl_FUNC_STRSTR
131