The value of inferior_ptid for remote debugging targets

[Dan Towner <dant at picochip dot com>]

Hi all,

I am porting gdb so that it can be used to debug remote debugging 
targets, which are embedded processors.  gdb communicates with the 
remote target using a monitor program, running on the same machine as 
gdb. Gdb invokes the monitor program using `serial_open', and uses pipes 
to communicate with it.

I am encountering a problem when I try to use watchpoints.  Whenever I 
set a watchpoint, the variable goes out of scope immediately I begin 
continuing the program being debugged. I have determined that the cause 
is the following code, which appears in blockframe.c:reinit_frame_cache

 /* FIXME: The inferior_ptid test is wrong if there is a corefile.  */
 if (PIDGET (inferior_ptid) != 0)
    {
      select_frame (get_current_frame (), 0);
    }

The inferior_ptid is 0 when this is called, hence the current frame is 
never selected. This in turn means that the current scope cannot be 
determined, and hence watchpoints don't work.

What is the correct value of inferior_ptid for remote targets, and why 
shouldn't the above code be called when a remote target is active? 
Should the inferior_ptid be setup so that the above code doesn't fail?

any help greatly appreciated...

dan.

=============================================================================
Daniel Towner
picoChip Designs Ltd., Riverside Buildings, 108, Walcot Street, BATH, 
BA1 5BG
dant@picochip.com
07786 702589