I am proposing a change to the to_stopped_data_address target vector function. 
There are two reasons.  The first reason is that there is no way to determine if 
a platform actually supports to_stopped_data_address.  For example, the S390 
supports hardware watchpoints, but doesn't support figuring out which address 
caused a watchpoint to trigger.  This level of detail is necessary for proper 
threaded watchpoint support to know whether to trust in the 
to_stopped_data_address function or whether to check all watchpoints for value 
changes.

The second reason for the proposed change is that there is no way to watch 
address 0 since to_stopped_data_address currently returns the address 0 to 
indicate failure.

The proposed change is to change the prototype to be:

int
to_stopped_data_address (CORE_ADDR *addr_p);

If the input pointer is NULL, the function returns non-zero if it works on the 
given target, otherwise, it fails by returning 0.  The function also returns 0 
if unsuccessful.  By separating out the success/fail code from the address, the 
new prototype allows for succeeding and returning any address, including 0.

Ok to commit?

-- Jeff J.

2004-08-31  Jeff Johnston  <jjohnstn@redhat.com>

         * target.h (to_stopped_data_address): Change prototype to
         take a CORE_ADDR pointer and return an int.
         * target.c (update_current_target): Change to_stopped_data_address
         to match new prototype.
         (debug_to_stopped_data_address): Change appropriately.
	* breakpoint.c (bpstat_stop_status): Change call to
	target_stopped_data_address to use new prototype.
         * frv-tdep.c (frv_have_stopped_data_address): New function.
         (frv_stopped_data_address): Change to new prototype and
         functionality.
         * ia64-linux-nat.c (ia64_stopped_data_address): Change to new
         prototype and functionality.
         (ia64_stopped_by_watchpoint): New function.
         * i386-nat.c (i386_stopped_data_address): Change to new
         prototype and functionality.
         (i386_stopped_by_watchpoint): New function.
         * remote.c (remote_stopped_data_address): Change to new prototype
         and functionality.
         * remote-m32r-sdi.c (m32r_stopped_data_address): Ditto.
         * config/frv/tm-frv.h (frv_stopped_data_address): Change prototype.
         (STOPPED_BY_WATCHPOINT): Change to use frv_have_stopped_data_address.
         * config/i386/nm-i386.h (STOPPED_BY_WATCHPOINT): Change to use
         new i386_stopped_by_watchpoint function.
         (i386_stopped_by_watchpoint): New prototype.
         (i386_stoppped_data_address): Change to new prototype.
         * config/ia64/nm-linux.h (STOPPED_BY_WATCHPOINT): Change to use
         new ia64_stopped_by_watchpoint function.
         (ia64_stopped_by_watchpoint): New prototype.
         (ia64_stopped_data_address): Ditto.

doc/ChangeLog:

2004-08-31  Jeff Johnston  <jjohnstn@redhat.com>

         * gdbint.texinfo (target_stopped_data_address): Update to
         new prototype.
         (i386_stopped_data_address): Update prototype and description.
         (i386_stopped_by_watchpoint): New function and description.