Re: valloc()?

Bruno Haible wrote:

>Derek Price wrote:
>
>
>>I've attached a patch to fix a few more nits
>>
>>
>
>Committed, with small wording tweaks in the comments.
>
>

Thanks.

>>    - Note in the header that pagealign_alloc sets errno on failure.
>>
>>
>
>But it doesn't do so if malloc() fails on non-POSIX systems (like mingw
>or so). I think one should set errno = ENOMEM if malloc() fails.
>
>

How about the attached patch?

>>I had two further thoughts on the naming of mmap-anon.m4.  First, in my
>>original decision to name it mmap.m4, I did take into consideration that
>>there might be other mmap.m4 implementations but, ideally, I would hope
>>that their requirements could be merged into this mmap(-anon).m4, at the
>>least for simplicity's sake.
>>
>>
>
>I don't have this hope: The requirements of different programs regarding
>mmap are so different that, if all tests were merged into a common mmap.m4
>file, some people would say "this test is insane - it disables mmap on
>SVR4 [or Linux 1.2 or HP-UX or ...] although it is perfectly sane".
>SVR4 had problems with PRIVATE READ-WRITE mappings of files.
>Linux 1.2 didn't support MAP_SHARED on files.
>HP-UX doesn't support mapping files at fixed addresses in most cases.
>
>

Okay, this makes sense.

>>Second, technically what we are currently
>>calling gl_FUNC_MMAP_ANON calls AC_FUNC_MMAP, so it also verifies that
>>private, fixed maps to files work as well, not just anonymous maps.
>>
>>
>
>Yes, this is one of the problems with AC_FUNC_MMAP. But fortunately we
>can ignore it because nowadays most systems have a working mmap(), therefore
>not many people will complain "it disables mmap() on my system".
>
>

Ok.  If it becomes an issue, CVS could currently get by with a call to
AC_CHECK_FUNC([mmap]) here, assuming that there are not any systems that
have mmaps which break for readonly, private, non-fixed maps.  Of
course, I've been meaning to move to writable mmaps soon, but that
addition could be made with a separate call to AC_FUNC_MMAP.

Regards,

Derek

_______________________________________________
bug-gnulib mailing list
[email protected]
http://lists.gnu.org/mailman/listinfo/bug-gnulib

Index: lib/pagealign_alloc.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/pagealign_alloc.c,v
retrieving revision 1.4
diff -u -p -r1.4 pagealign_alloc.c
--- lib/pagealign_alloc.c	3 Mar 2005 20:38:38 -0000	1.4
+++ lib/pagealign_alloc.c	3 Mar 2005 21:13:29 -0000
@@ -147,9 +147,16 @@ pagealign_alloc (size_t size)
     }
 #else /* !HAVE_MMAP && !HAVE_POSIX_MEMALIGN */
   size_t pagesize = getpagesize ();
-  void *unaligned_ptr = malloc (size + pagesize - 1);
+  void *unaligned_ptr;
+  errno = 0;
+  unaligned_ptr = malloc (size + pagesize - 1);
   if (unaligned_ptr == NULL)
-    return NULL;
+    {
+      /* Failed malloc on some non-posix systems (e.g. mingw) fail to set
+         errno.  */
+      if (!errno) errno = ENOMEM;
+      return NULL;
+    }
   ret = (char *) unaligned_ptr
         + ((- (unsigned long) unaligned_ptr) & (pagesize - 1));
   new_memnode (ret, unaligned_ptr);

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.0 (Cygwin)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFCJ4AmLD1OTBfyMaQRArRrAJ455wMmmmKRO41vHbgFuwsiwMRcXACghP9e
KCLChgKOaR+CLGYxN2DdKEk=
=nUuO
-----END PGP SIGNATURE-----