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[please limit replies about the patch itself to autoconf-patches]
According to Corinna Vinschen on 11/9/2009 7:05 AM:
> This part of the testcase
>
> data2 = (char *) malloc (2 * pagesize);
> if (!data2)
> return 1;
> data2 += (pagesize - ((long int) data2 & (pagesize - 1))) & (pagesize - 1);
> if (data2 != mmap (data2, pagesize, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_FIXED, fd, 0L))
> return 1;
>
> is bad. The chance that the address of data2 is not usable for mmap on
> Windows/Cygwin is 100%. The problem here is that the generic HAVE_MMAP
> test tests one certain feature, which is not usable on Windows, and which
> is non-portable.
MAP_FIXED appears to be more portable when the fixed address was obtained
from a previous mmap call. Therefore, this patch fixes the macro as well
as making diagnosing configure failures more accurately pinpoint why they
are declaring failure. I don't have access to HP-UX 11, which is another
platform where AC_FUNC_MMAP was failing; I would appreciate if someone
else could see if this makes a difference there. But I have verified that
this now sets HAVE_MMAP for cygwin 1.5.x and cygwin 1.7 where the old
version failed, and that it does not change behavior on Linux or OpenBSD.
- --
Don't work too hard, make some time for fun as well!
Eric Blake e...@byu.net
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>From fb1f28a2ff2c688e63dc97ece7fde86e16864491 Mon Sep 17 00:00:00 2001
From: Eric Blake <e...@byu.net>
Date: Mon, 9 Nov 2009 21:45:00 -0700
Subject: [PATCH] Fix AC_FUNC_MMAP for cygwin.
* lib/autoconf/functions.m4 (AC_FUNC_MMAP): Make the test more
portable: Actually check for <sys/param.h>, and only use MAP_FIXED
on an address previously returned from mmap.
* THANKS: Update.
Reported by Corinna Vinschen.
Signed-off-by: Eric Blake <e...@byu.net>
---
ChangeLog | 9 +++++++
NEWS | 3 ++
lib/autoconf/functions.m4 | 55 ++++++++++++++++++++++++++------------------
3 files changed, 44 insertions(+), 23 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 4d028c0..77e9d4e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2009-11-09 Eric Blake <e...@byu.net>
+
+ Fix AC_FUNC_MMAP for cygwin.
+ * lib/autoconf/functions.m4 (AC_FUNC_MMAP): Make the test more
+ portable: Actually check for <sys/param.h>, and only use MAP_FIXED
+ on an address previously returned from mmap.
+ * THANKS: Update.
+ Reported by Corinna Vinschen.
+
2009-11-04 Eric Blake <e...@byu.net>
Redocument AS_DIRNAME, even with its flaws.
diff --git a/NEWS b/NEWS
index 9e7e64c..86a0c3f 100644
--- a/NEWS
+++ b/NEWS
@@ -29,6 +29,9 @@ GNU Autoconf NEWS - User visible changes.
longer mistakenly select a 32-bit type on some compilers (bug present
since macros were introduced in 2.59c).
+** The AC_FUNC_MMAP macro has been fixed to be portable to systems like
+ Cygwin (bug present since macro was introduced in 2.0).
+
** The following documented autotest macros are new:
AT_CHECK_EUNIT
diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 946a646..6b6e7fc 100644
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -1186,9 +1186,9 @@ AU_ALIAS([AM_FUNC_MKTIME], [AC_FUNC_MKTIME])
# ------------
AN_FUNCTION([mmap], [AC_FUNC_MMAP])
AC_DEFUN([AC_FUNC_MMAP],
-[AC_CHECK_HEADERS(stdlib.h unistd.h)
-AC_CHECK_FUNCS(getpagesize)
-AC_CACHE_CHECK(for working mmap, ac_cv_func_mmap_fixed_mapped,
+[AC_CHECK_HEADERS_ONCE([stdlib.h unistd.h sys/param.h])
+AC_CHECK_FUNCS([getpagesize])
+AC_CACHE_CHECK([for working mmap], [ac_cv_func_mmap_fixed_mapped],
[AC_RUN_IFELSE([AC_LANG_SOURCE([AC_INCLUDES_DEFAULT]
[[/* malloc might have been renamed as rpl_malloc. */
#undef malloc
@@ -1224,11 +1224,6 @@ char *malloc ();
/* This mess was copied from the GNU getpagesize.h. */
#ifndef HAVE_GETPAGESIZE
-/* Assume that all systems that can run configure have sys/param.h. */
-# ifndef HAVE_SYS_PARAM_H
-# define HAVE_SYS_PARAM_H 1
-# endif
-
# ifdef _SC_PAGESIZE
# define getpagesize() sysconf(_SC_PAGESIZE)
# else /* no _SC_PAGESIZE */
@@ -1264,7 +1259,7 @@ main ()
{
char *data, *data2, *data3;
int i, pagesize;
- int fd;
+ int fd, fd2;
pagesize = getpagesize ();
@@ -1277,27 +1272,41 @@ main ()
umask (0);
fd = creat ("conftest.mmap", 0600);
if (fd < 0)
- return 1;
+ return 2;
if (write (fd, data, pagesize) != pagesize)
- return 1;
+ return 3;
close (fd);
+ /* Next, check that the tail of a page is zero-filled. File must have
+ non-zero length, otherwise we risk SIGBUS for entire page. */
+ fd2 = open ("conftest.txt", O_RDWR | O_CREAT | O_TRUNC, 0600);
+ if (fd2 < 0)
+ return 4;
+ data2 = "";
+ if (write (fd2, data2, 1) != 1)
+ return 5;
+ data2 = mmap (0, pagesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd2, 0L);
+ if (data2 == MAP_FAILED)
+ return 6;
+ for (i = 0; i < pagesize; ++i)
+ if (*(data2 + i))
+ return 7;
+ close (fd2);
+ if (munmap (data2, pagesize))
+ return 8;
+
/* Next, try to mmap the file at a fixed address which already has
something else allocated at it. If we can, also make sure that
we see the same garbage. */
fd = open ("conftest.mmap", O_RDWR);
if (fd < 0)
- return 1;
- data2 = (char *) malloc (2 * pagesize);
- if (!data2)
- return 1;
- data2 += (pagesize - ((long int) data2 & (pagesize - 1))) & (pagesize - 1);
+ return 9;
if (data2 != mmap (data2, pagesize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_FIXED, fd, 0L))
- return 1;
+ return 10;
for (i = 0; i < pagesize; ++i)
if (*(data + i) != *(data2 + i))
- return 1;
+ return 11;
/* Finally, make sure that changes to the mapped area do not
percolate back to the file as seen by read(). (This is a bug on
@@ -1306,12 +1315,12 @@ main ()
*(data2 + i) = *(data2 + i) + 1;
data3 = (char *) malloc (pagesize);
if (!data3)
- return 1;
+ return 12;
if (read (fd, data3, pagesize) != pagesize)
- return 1;
+ return 13;
for (i = 0; i < pagesize; ++i)
if (*(data + i) != *(data3 + i))
- return 1;
+ return 14;
close (fd);
return 0;
}]])],
@@ -1319,10 +1328,10 @@ main ()
[ac_cv_func_mmap_fixed_mapped=no],
[ac_cv_func_mmap_fixed_mapped=no])])
if test $ac_cv_func_mmap_fixed_mapped = yes; then
- AC_DEFINE(HAVE_MMAP, 1,
+ AC_DEFINE([HAVE_MMAP], [1],
[Define to 1 if you have a working `mmap' system call.])
fi
-rm -f conftest.mmap
+rm -f conftest.mmap conftest.txt
])# AC_FUNC_MMAP
--
1.6.5.rc1
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