maint: update copyright

[gnulib.git] / tests / zerosize-ptr.h

diff --git a/tests/zerosize-ptr.h b/tests/zerosize-ptr.h
index fa00aee..db30f4b 100644 (file)
--- a/tests/zerosize-ptr.h
+++ b/tests/zerosize-ptr.h
@@ -1,5 +1,5 @@
 /* Return a pointer to a zero-size object in memory.
-   Copyright (C) 2009 Free Software Foundation, Inc.
+   Copyright (C) 2009-2014 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -20,7 +20,11 @@
 
 #include <stdlib.h>
 
-#if HAVE_MPROTECT
+/* Test whether mmap() and mprotect() are available.
+   We don't use HAVE_MMAP, because AC_FUNC_MMAP would not define it on HP-UX.
+   HAVE_MPROTECT is not enough, because mingw does not have mmap() but has an
+   mprotect() function in libgcc.a.  */
+#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
 # include <fcntl.h>
 # include <unistd.h>
 # include <sys/types.h>
@@ -31,7 +35,9 @@
 # endif
 #endif
 
-/* Return a pointer to a zero-size object in memory, if possible.
+/* Return a pointer to a zero-size object in memory (that is, actually, a
+   pointer to a page boundary where the previous page is readable and writable
+   and the next page is neither readable not writable), if possible.
    Return NULL otherwise.  */
 
 static void *
@@ -39,7 +45,7 @@ zerosize_ptr (void)
 {
 /* Use mmap and mprotect when they exist.  Don't test HAVE_MMAP, because it is
    not defined on HP-UX 11 (since it does not support MAP_FIXED).  */
-#if HAVE_MPROTECT
+#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
 # if HAVE_MAP_ANONYMOUS
   const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
   const int fd = -1;
@@ -51,11 +57,11 @@ zerosize_ptr (void)
     {
       int pagesize = getpagesize ();
       char *two_pages =
-       (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
-                      flags, fd, 0);
+        (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)
-       return two_pages + pagesize;
+          && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
+        return two_pages + pagesize;
     }
 #endif
   return NULL;