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* gdb/2499: to_can_use_hw_breakpoint/CAN_USE_HARDWARE_WATCHPOINT ambiguous
@ 2008-08-12 6:38 jeremy.bennett
0 siblings, 0 replies; only message in thread
From: jeremy.bennett @ 2008-08-12 6:38 UTC (permalink / raw)
To: gdb-gnats; +Cc: jeremy.bennett
>Number: 2499
>Category: gdb
>Synopsis: to_can_use_hw_breakpoint/CAN_USE_HARDWARE_WATCHPOINT ambiguous
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Tue Aug 12 06:38:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator: jeremy.bennett@embecosm.com
>Release: unknown-1.0
>Organization:
>Environment:
Fedora 9 Linux, GDB 6.8, OpenRISC 1000 (or1k) target
>Description:
The code to set a watchpoint in watch_command_1() tests to see if a hardware watchpoint is available, using CAN_USE_HARDARE_WATCHPOINT, which in turn calls the to_can_use_hw_breakpoint() function of the target.
This returns 0 to indicate that the particular type of watchpoint is unsupported and -1 to indicate either that there are insufficient watchpoint resources or that two different types of watchpoint cannot simultaneously be supported. However for the latter case the error message given is always:
"Target can only support one kind of HW watchpoint at a time."
This is confusing if the problem is actually that the resources have run out.
This bug is related to Bug 967, concerning the need to pass to_can_use_hw_breakpoint() additional information for it to make a good judgement.
Not a high priority, but entered here for the record.
>How-To-Repeat:
At present I can only demonstrate this with the GDB 6.8 port for the OpenRISC architecture, which supports a maximum of 4 watchpoints:
(gdb) rwatch a
Hardware read watchpoint 1: a
(gdb) rwatch b
Hardware read watchpoint 2: b
(gdb) rwatch c
Hardware read watchpoint 3: c
(gdb) rwatch d
Hardware read watchpoint 4: d
(gdb) rwatch e
Target can only support one kind of HW watchpoint at a time.
(gdb)
It should occur for any architecture with finite hardware watchpoint resources.
>Fix:
I suggest to_can_use_hw_breakpoint() specification is extended to allow return -2 to indicate resources have run out with -1 reserved for its current meaning. The code in watch_command_1() could then be extended to print out the appropriate message in each case. This would be backwards compatible with the existing code base.
>Release-Note:
>Audit-Trail:
>Unformatted:
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2008-08-12 6:38 gdb/2499: to_can_use_hw_breakpoint/CAN_USE_HARDWARE_WATCHPOINT ambiguous jeremy.bennett
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