Re: ARM/linux gdb stops and gives no info

[Fernando Nasser <fnasser at cygnus dot com>]

Richard Earnshaw wrote:
> 
> >
> > Richard Earnshaw <rearnsha@arm.com> wrote:
> >
> > > I can understand not being able to unpick the stack frame if I've jumped
> > > to never-never land, but to not even be able to display the registers
> > > makes the debugger useless.
> >
> > Have you tried "print $pc", "print $r1", ... to get the register contents?
> >
> 
> Thanks for the tip: yes, that works.  However, I still think that "info
> reg" should display the raw registers if there is no valid stack frame.
> 

Peter Schauer added the test for NULL frames in there back in 1995.  I believe
it was causing core dumps, but I am not sure as the ChangeLog entry does not give
the motive (we nowadays make sure it does, but that was not always true at the time):

     * infcmd.c (registers_info):  Error out if selected_frame is NULL.

I believe the default gdb routine (if the target does not define DO_REGISTERS_INFO)
does not depend on selected_frame but I can't be sure about all targets.

I quickly created the patch below.  I have no time to test it these days.
If you care applying it to your sources and trying I would appreciate.
Otherwise it goes in my 25 pages long TODO list.. ;-)

Regards,
Fernando

-- 
Fernando Nasser
Red Hat - Toronto                       E-Mail:  fnasser@cygnus.com
2323 Yonge Street, Suite #300           Tel:  416-482-2661 ext. 311
Toronto, Ontario   M4P 2C9              Fax:  416-482-6299



Index: infcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/infcmd.c,v
retrieving revision 1.1.1.17
diff -c -p -r1.1.1.17 infcmd.c
*** infcmd.c    2000/02/03 04:14:31     1.1.1.17
--- infcmd.c    2000/05/30 13:42:23
*************** char *gdb_register_names[] = REGISTER_NA
*** 1494,1501 ****
     is required, (eg, for MIPS or Pyramid 90x, which both have
     lots of regs), or there is an existing convention for showing
     all the registers, define the macro DO_REGISTERS_INFO(regnum, fp)
!    to provide that format.  */
  
  #if !defined (DO_REGISTERS_INFO)
  
  #define DO_REGISTERS_INFO(regnum, fp) do_registers_info(regnum, fp)
--- 1494,1504 ----
     is required, (eg, for MIPS or Pyramid 90x, which both have
     lots of regs), or there is an existing convention for showing
     all the registers, define the macro DO_REGISTERS_INFO(regnum, fp)
!    to provide that format.
  
+    This default routine must work even if there is no selected_frame (== NULL).
+    Please don't add any dependencies on that being defined. */
+ 
  #if !defined (DO_REGISTERS_INFO)
  
  #define DO_REGISTERS_INFO(regnum, fp) do_registers_info(regnum, fp)
*************** registers_info (addr_exp, fpregs)
*** 1617,1624 ****
--- 1620,1633 ----
  
    if (!target_has_registers)
      error ("The program has no registers now.");
+ 
+ #if !defined (DO_REGISTERS_INFO)
+   /* The default do_registers_info() does not need the selected_frame
+      so we don't test for it not being NULL. Tagets that define
+      DO_REGISTERS_INFO may rely on that, so we make sure it is valid. */
    if (selected_frame == NULL)
      error ("No selected frame.");
+ #endif
  
    if (!addr_exp)
      {