recurse.exp: watch on local variable that goes out of scope

Orjan Friberg
2004-07-20T14:37:23Z

I'm having problems with recurse.exp on CRISv32 with hardware watchpoint support
- a local variable which goes out of scope isn't handled the same way as on the
i386 ("second instance watchpoint deleted when leaving scope"). On the i386
i386_stopped_data_address returns a proper address when I don't expect it to.

Here's a recap of what I think I've understood: in order to detect when a
watched local variable goes out of scope, gdb inserts a breakpoint on the
instruction where the function that the variable belongs to returns to. In this
case it shows up as ("maint info break"; local variable "b" is watched in
recurse (a=5)):

4 hw watchpoint keep y b
breakpoint already hit 2 times
-56 watchpoint scope del y 0x08048403 <recurse+51>
stop only in stack frame at 0xbffff4c4
breakpoint already hit 4 times

When stopped at the return statement of recurse (a=5), a continue is issued,
making recurse (a=5) return and the "watchpoint scope del" breakpoint is then
hit (the bp_addr argument to bpstat_stop_status == 0x08048403).

Now for the confusing part: bpstat_stop_status is called with
stopped_by_watchpoint == 1. This is because, at this point,
i386_stopped_data_address returns the address of the local variable "b" (the
address it had in recurse (a=5)), as if it were stopped due to a watchpoint hit.
I would have expected i386_stopped_data_address to return 0 at this point,
since it didn't stop due to a watchpoint hit. What am I missing here? Does
i386_stopped_data_address retain the stopped data address from the previous hit?

Thanks in advance.