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

diff --git a/tests/zerosize-ptr.h b/tests/zerosize-ptr.h
index 9918ac7..f0e6155 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) 2009-2013 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
@@ -35,7 +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 *
@@ -55,11 +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;