kc3-lang/gnulib/m4/memchr.m4

• Show log

  Commit

• Hash : 32a72f45
  Author :
  Date : 2023-01-01T01:14:21
  

  maint: run 'make update-copyright'
  

Download

• m4/memchr.m4

• # memchr.m4 serial 18
  dnl Copyright (C) 2002-2004, 2009-2023 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_ONCE([gl_FUNC_MEMCHR],
  [
    AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  
    dnl Check for prerequisites for memory fence checks.
    gl_FUNC_MMAP_ANON
    AC_CHECK_HEADERS_ONCE([sys/mman.h])
    AC_CHECK_FUNCS_ONCE([mprotect])
  
    AC_REQUIRE([gl_STRING_H_DEFAULTS])
    # Detect platform-specific bugs in some versions of glibc:
    # memchr should not dereference anything with length 0
    #   https://bugzilla.redhat.com/show_bug.cgi?id=499689
    # memchr should not dereference overestimated length after a match
    #   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
    #   https://sourceware.org/bugzilla/show_bug.cgi?id=10162
    # memchr should cast the second argument to 'unsigned char'.
    #   This bug exists in Android 4.3.
    # Assume that memchr works on platforms that lack mprotect.
    AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
  #include <string.h>
  #if HAVE_SYS_MMAN_H
  # include <fcntl.h>
  # include <unistd.h>
  # include <sys/types.h>
  # include <sys/mman.h>
  # ifndef MAP_FILE
  #  define MAP_FILE 0
  # endif
  #endif
  ]], [[
    int result = 0;
    char *fence = NULL;
  #if HAVE_SYS_MMAN_H && HAVE_MPROTECT
  # if HAVE_MAP_ANONYMOUS
    const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
    const int fd = -1;
  # else /* !HAVE_MAP_ANONYMOUS */
    const int flags = MAP_FILE | MAP_PRIVATE;
    int fd = open ("/dev/zero", O_RDONLY, 0666);
    if (fd >= 0)
  # endif
      {
        int pagesize = getpagesize ();
        char *two_pages =
          (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
                         flags, fd, 0);
        if (two_pages != (char *)(-1)
            && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
          fence = two_pages + pagesize;
      }
  #endif
    if (fence)
      {
        /* Test against bugs on glibc systems.  */
        if (memchr (fence, 0, 0))
          result |= 1;
        strcpy (fence - 9, "12345678");
        if (memchr (fence - 9, 0, 79) != fence - 1)
          result |= 2;
        if (memchr (fence - 1, 0, 3) != fence - 1)
          result |= 4;
        /* Test against bug on AIX 7.2.  */
        if (memchr (fence - 4, '6', 16) != fence - 4)
          result |= 8;
      }
    /* Test against bug on Android 4.3.  */
    {
      char input[3];
      input[0] = 'a';
      input[1] = 'b';
      input[2] = 'c';
      if (memchr (input, 0x789abc00 | 'b', 3) != input + 1)
        result |= 16;
    }
    return result;
  ]])],
         [gl_cv_func_memchr_works=yes],
         [gl_cv_func_memchr_works=no],
         [case "$host_os" in
                             # Guess no on Android.
            linux*-android*) gl_cv_func_memchr_works="guessing no" ;;
                             # Guess yes on native Windows.
            mingw*)          gl_cv_func_memchr_works="guessing yes" ;;
                             # If we don't know, obey --enable-cross-guesses.
            *)               gl_cv_func_memchr_works="$gl_cross_guess_normal" ;;
          esac
         ])
      ])
    case "$gl_cv_func_memchr_works" in
      *yes) ;;
      *) REPLACE_MEMCHR=1 ;;
    esac
  ])
  
  # Prerequisites of lib/memchr.c.
  AC_DEFUN([gl_PREREQ_MEMCHR], [
    AC_CHECK_HEADERS([bp-sym.h])
  ])
  

Download