Re: [PATCH] Fix building gdb-7.0 on x86_64-*-freebsd

[Steve Kargl <sgk@troutmask.apl.washington.edu>]

On Mon, Oct 19, 2009 at 09:53:07PM +0200, Joel Brobecker wrote:
> Hi Sergio,
> 
> > Thank you for this patch.  I believe you could add a comment explaining what 
> > this number means (just like you did above).  What do you think?
> > Just my two cents, as usual :-).
> 
> I just applied the following patch (head only)
> 
> 2009-10-19  Joel Brobecker  <brobecker@adacore.com>
> 
>         * amd64fbsd-nat.c (amd64fbsd_supply_pcb): Add comment.
> 
> Writing the comment made me think that we may have chosen the wrong
> version number, depending on the angle we look at things from: If we
> want to always be able to build, then we should have chosen version
> 74, since there are a few days where version 74 is missing the field
> and yet the GDB code still tries to access it for that versio number.
> However, if we're trying to have our code always use these fields
> whenver possible, then 75 is the right choice. Although we'll fail
> to build for any sources that's in between the moment the fields were
> removed and the moment the version was bumped to 75 (a time period
> of about a few days), we'll be able use these fields for the rest
> of version 74 of the sources.
> 
> Based on the number of days this window is open, I would say that this
> situation is highly unlikely, and so we don't really need to worry about
> it.
> 

You may be correct that a different version should have been used.
OTOH, gdb-6.8 was released on 2008-02-29 and the problematic code
is present in 6.8.  I haven't seen anyone complain on the FreeBSD
mailing lists that they can't build 6.8.  In looking at FreeBSD's
Port Collection, I find /usr/ports/devel/gdb6.  This still uses the
gdb 6.6 tarball.  In looking at the port, I find

troutmask:sgk[228] cd /usr/ports/devel/gdb6
troutmask:sgk[229] more files/patch-gdb-amd64fbsd-nat.c 
--- gdb/amd64fbsd-nat.c.orig    2005-12-17 17:33:59.000000000 -0500
+++ gdb/amd64fbsd-nat.c 2009-09-10 02:29:33.000000000 -0400
@@ -125,10 +125,12 @@
   regcache_raw_supply (regcache, 13, &pcb->pcb_r13);
   regcache_raw_supply (regcache, 14, &pcb->pcb_r14);
   regcache_raw_supply (regcache, 15, &pcb->pcb_r15);
+#if defined(__FreeBSD_version) && __FreeBSD_version < 800000
   regcache_raw_supply (regcache, AMD64_DS_REGNUM, &pcb->pcb_ds);
   regcache_raw_supply (regcache, AMD64_ES_REGNUM, &pcb->pcb_es);
   regcache_raw_supply (regcache, AMD64_FS_REGNUM, &pcb->pcb_fs);
   regcache_raw_supply (regcache, AMD64_GS_REGNUM, &pcb->pcb_gs);
+#endif
 
   return 1;
 }

Apparently, whoever is responsible for this port never 
forwarded their patch upstream to the gdb developers.
Oh well. 

-- 
Steve