[MPlayer-dev-eng] [PATCH] (loader/ext.c) VirtualAlloc() SIGSEGV on Linux + other fixes

[A. Guru]

* On Monday 2004-08-16 at 15:07:02 +0300, Jan Knutar wrote:
> On Monday 16 August 2004 12:22, A. Guru wrote:
> > Changes:
> > 
> >     * mplayer received a SIGSEGV under Linux after
> > 
> > 	Opening video decoder: [dmo] DMO video codecs
> > 	VirtualAlloc(0x00400000, 859648, 0x00003000, 0x00000040)
> > 
> >       with
> > 
> > 	-rw-r--r--  1 root root 807032 Nov 20  2002 /usr/local/lib/codecs/wmv9dmod.dll
> > 
> >       because that region was already under use and mmap() with MAP_FIXED has
> >       problems under Linux (see code).  VirtualAlloc() fixed in "loader/ext.c".
> > 
> >     * VirtualAlloc() made to conform with win32 documented behavior regarding
> >       the alignment of the address and size arguments.
> > 
> >     * VirtualAlloc() detection of overlap with previous regions fixed.
> 
> Does this do same thing as
> http://article.gmane.org/gmane.comp.video.mplayer.devel/18464
> 
> Or are these two separate issues?

Issue 2 and 3 are different and deserve individual attention.

The first issue is the same, but the solution is more portable (does
not depend on a specific file in /proc, or the very presence of /proc),
will work in a long-running (g)mplayer process (does not depend on
an initial snapshot of the process' memory maps, which may evolve),
and is less intrusive (if the lines dealing with issue 2 and 3 and the
printf()s are ignored).


I have checked and mmap() with MAP_FIXED will have problems with POSIX systems in
general, not just Linux.  See

	<http://www.opengroup.org/onlinepubs/009695399/functions/mmap.html>

and in particular the whole paragraph that starts with "If an application
requests a mapping that would overlay existing mappings...", in particular
"new mappings replace any existing mappings".


Nevertheless, if this other patch using /proc were retained, it should
use /proc/self/maps instead of computing a string with the pid in it.
However, Solaris /proc has the /proc/self/map and /proc/self/rmap files
and I don't think they are text, but binary.