Re: PATCH to define TARGET_READ_PC for MIPS

[Andrew Cagney <ac131313 at cygnus dot com>]

Hello,

While I can see what you're doing and it is a pretty neat trick, I don't
think it is reasonable to change GDB so that missleads the user about
the current $pc value.

While more complex, I think the stack dump code is the thing to be
changed.

sorry,
	Andrew



Greg McGary wrote:
> 
> 2000-01-13  Greg McGary  <gkm@gnu.org>
> 
>         * gdb/config/mips/tm-mips.h (TARGET_READ_PC): if PC==BADVA, return RA.
> 
> Index: config/mips/tm-mips.h
> ===================================================================
> RCS file: /cvs/gdb/gdb/gdb/config/mips/tm-mips.h,v
> retrieving revision 1.1.1.11
> diff -u -p -r1.1.1.11 tm-mips.h
> --- tm-mips.h   1999/12/22 21:45:14     1.1.1.11
> +++ tm-mips.h   2000/01/14 02:01:22
> @@ -1,5 +1,5 @@
>  /* Definitions to make GDB run on a mips box under 4.3bsd.
> -   Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995
> +   Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 2000
>     Free Software Foundation, Inc.
>     Contributed by Per Bothner (bothner@cs.wisc.edu) at U.Wisconsin
>     and by Alessandro Forin (af@cs.cmu.edu) at CMU..
> @@ -73,6 +73,18 @@ CORE_ADDR mips_addr_bits_remove PARAMS (
>  /* Remove useless bits from the stack pointer.  */
> 
>  #define TARGET_READ_SP() ADDR_BITS_REMOVE (read_register (SP_REGNUM))
> +
> +/* If the value of PC_REGNUM equals that of BADVADDR_REGNUM, then we
> +   crashed because of a function call through a stray pointer, and
> +   we're doomed to fail if we try to trace the stack from that PC.
> +   When this happens, RA_REGNUM contains the return address from which
> +   the bad call was made, and is a fine place to start tracing.  */
> +
> +#define TARGET_READ_PC(PID)                                            \
> +  ADDR_BITS_REMOVE ((read_register_pid (PC_REGNUM, (PID))              \
> +                    == read_register_pid (BADVADDR_REGNUM, (PID)))     \
> +                   ? read_register_pid (RA_REGNUM, (PID))              \
> +                   : read_register_pid (PC_REGNUM, (PID)))
> 
>  /* Offset from address of function to start of its code.
>     Zero on most machines.  */