Re: 21.2 startup crash on Irix

["Eli Zaretskii" <eliz@is.elta.co.il>]

> From: Dave Love <d.love@dl.ac.uk>
> Date: 16 Apr 2002 22:27:50 +0100
> 
> > If this helps, please try the change suggested yesterday by Robert A
> > Basch <rbasch@MIT.EDU> in the thread "Emacs 21 mmap problem" in this
> > group.
> 
> I'm not reading a group.  Please send a reference I can follow if you
> want me to read it.

Since I wrote that, Gerd installed a change (on RC as well), so you
can have it with "cvs up".  I attach the diffs for the release branch
below.

> However, I had backed out the mmap changes as well as the .got ones
> to no effect.

The changes I had in mind are not related to unexec, as you will see
from the diffs.

2002-04-16  Gerd Moellmann  <gerd@gnu.org>

	* buffer.c (MMAP_ALLOCATED_P): New macro to be set from system
	configuration files.
	(mmap_enlarge): Enlarge mapped regions only if MMAP_ALLOCATED_P
	returns 0.

Index: src/buffer.c
===================================================================
RCS file: /cvs/emacs/src/buffer.c,v
retrieving revision 1.358.4.3
retrieving revision 1.358.4.4
diff -u -r1.358.4.3 -r1.358.4.4
--- src/buffer.c	28 Jan 2002 16:56:03 -0000	1.358.4.3
+++ src/buffer.c	16 Apr 2002 07:36:19 -0000	1.358.4.4
@@ -1,5 +1,5 @@
 /* Buffer manipulation primitives for GNU Emacs.
-   Copyright (C) 1985,86,87,88,89,93,94,95,97,98, 1999, 2000, 2001
+   Copyright (C) 1985,86,87,88,89,93,94,95,97,98, 1999, 2000, 2001, 2002
 	Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -4277,6 +4277,18 @@
 
 #define MEM_ALIGN	sizeof (double)
 
+/* Predicate returning true if part of the address range [START ..
+   END[ is currently mapped.  Used to prevent overwriting an existing
+   memory mapping.
+
+   Default is to conservativly assume the address range is occupied by
+   something else.  This can be overridden by system configuration
+   files if system-specific means to determine this exists.  */
+
+#ifndef MMAP_ALLOCATED_P
+#define MMAP_ALLOCATED_P(start, end) 1
+#endif
+
 /* Function prototypes.  */
 
 static int mmap_free_1 P_ ((struct mmap_region *));
@@ -4369,16 +4381,13 @@
     }
   else if (npages > 0)
     {
-      struct mmap_region *r2;
-      
       nbytes = npages * mmap_page_size;
       
       /* Try to map additional pages at the end of the region.  We
 	 cannot do this if the address range is already occupied by
 	 something else because mmap deletes any previous mapping.
 	 I'm not sure this is worth doing, let's see.  */
-      r2 = mmap_find (region_end, region_end + nbytes);
-      if (r2 == NULL)
+      if (!MMAP_ALLOCATED_P (region_end, region_end + nbytes))
 	{
 	  POINTER_TYPE *p;