[RFA/RFC] mips tracepoint: fix Bug 12013

[Pedro Alves]

On Tuesday 28 December 2010 17:08:52, Joel Brobecker wrote:
> > Joel,  do you think this patch can check in to 7.2.1.
> 
> I think that it's borderline, and I'm tempted to say no, considering
> that this is not a crash or a regression (just a limitation).  But
> it looks relatively safe to me.  So, if Pedro agrees, it's OK with me.

Yeah.  I understand that without this patch, MIPS tracepoints are
practically useless on 7.2, so on those grounds, I'd be okay.

However, I just went to check whether collecting a pseudo or
user register in x86/x86_64 still gives a reasonable error, and
I now get:

 >./gdb -q ./gdb
 Reading symbols from /home/pedro/gdb/baseline/build/gdb/gdb...done.
 (top-gdb) start
 Temporary breakpoint 3 at 0x4565c3: file ../../src/gdb/gdb.c, line 29.
 Starting program: /home/pedro/gdb/baseline/build/gdb/gdb 
 [Thread debugging using libthread_db enabled]

 Temporary breakpoint 3, main (argc=1, argv=0x7fffffffe108) at ../../src/gdb/gdb.c:29
 29        memset (&args, 0, sizeof args);
 (top-gdb) maint agent $sp
 ../../src/gdb/regcache.c:166: internal-error: register_type: Assertion `regnum >= 0 && regnum < descr->nr_cooked_registers' failed.
 A problem internal to GDB has been detected,
 further debugging may prove unreliable.
 Quit this debugging session? (y or n) 

While before (on 7.2), we'd get:

 (top-gdb) maint agent $sp
 'sp' is a pseudo-register; GDB cannot yet trace pseudoregister contents.

We'll need to get this fixed this before considering a backport to 7.2.

-- 
Pedro Alves