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Re: breakpoints/1321: GDB: problem with FPU


The following reply was made to PR breakpoints/1321; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: Mark Kettenis <kettenis@chello.nl>, gdb-gnats@sources.redhat.com
Cc:  
Subject: Re: breakpoints/1321: GDB: problem with FPU
Date: Sun, 4 Jan 2004 12:39:42 -0500

 On Sun, Jan 04, 2004 at 10:38:00AM -0000, Mark Kettenis wrote:
 > The following reply was made to PR breakpoints/1321; it has been noted by GNATS.
 > 
 > From: Mark Kettenis <kettenis@chello.nl>
 > To: gdb-gnats@sources.redhat.com, miwako.tokugawa@intel.com, sana@stl.sarov.ru
 > Cc:  
 > Subject: Re: breakpoints/1321: GDB: problem with FPU
 > Date: Sun, 4 Jan 2004 11:35:04 +0100 (CET)
 > 
 >  I'm fairly certain this problem is related to the lack of support for
 >  FXSAVE/SSE in libthread_db on Linux.  As a result the SSE and FPU
 >  registers don't get passed along correctly between the different
 >  layers when debugging threaded programs.  Consequently you're looking
 >  at stale FPU registers or FPU registers from a different thread.  The
 >  problem will probably go away when debugging on an older machine that
 >  doesn't have the SSE registers.
 >  
 >  We can't fix this until someone adds the necessary bits to
 >  libthread_db, which can be found in glibc.
 
 I don't think so - libthread_db will (with one exception) just pass an
 arbitrary size of regset through.  This particular bug was fixed two
 years ago, I think.  It was a nasty little bug that (IIRC) caused the
 wrong thread's registers to be written back after a single-step.
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer


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