X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=tests%2Fzerosize-ptr.h;h=a38a2cf4941ab810d59019f69b9458f8d66bcebe;hb=4e42b89b090f61e189e7161a3f096cabc832b6d3;hp=fa00aeeee5d6e63824432a410df93371f3f77cdb;hpb=bb051a0a3c0febe9d3fabb21ae5b7fcc2ae7aa10;p=gnulib.git

diff --git a/tests/zerosize-ptr.h b/tests/zerosize-ptr.h
index fa00aeeee..a38a2cf49 100644
--- a/tests/zerosize-ptr.h
+++ b/tests/zerosize-ptr.h
@@ -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;