Re: [PATCH v5] [PR python/29603] Disable out-of-scope watchpoints

[Johnson Sun <j3.soon777@gmail.com>]

Hi,

I just applied the patch to commit 
39453f9d8cf03b382d34f3548706f1ae5916e34e, and tested with the following 
commands on a clean Ubuntu 22.04 LTS machine:

     make check TESTS="gdb.python/py-watchpoint.exp"
     make check TESTS="gdb.python/py-watchpoint.exp" 
RUNTESTFLAGS="--target_board=native-gdbserver"
     make check TESTS="gdb.python/py-watchpoint.exp" 
RUNTESTFLAGS="--target_board=native-extended-gdbserver"

all 3 commands above passed the tests (10/10) on my machine.

I'm unsure why the test times out on your machine. Could you provide 
information regarding the base commit that was used and the operating 
system installed?

Best regards,
Johnson

On 5/10/2023 2:50 AM, SimonMarchi wrote:
> On 4/23/23 05:54, Johnson Sun wrote:
>> Currently, when a local software watchpoint goes out of scope, GDB sets
>> the watchpoint's disposition to `delete at next stop' and then normal
>> stops (i.e., stop and wait for the next GDB command). When GDB normal
>> stops, it automatically deletes the breakpoints with their disposition
>> set to `delete at next stop'.
>>
>> Suppose a Python script decides not to normal stop when a local
>> software watchpoint goes out of scope, the watchpoint will not be
>> automatically deleted even when its disposition is set to
>> `delete at next stop'.
>>
>> Since GDB single-steps the program and tests the watched expression
>> after each instruction, not deleting the watchpoint causes the
>> watchpoint to be hit many more times than it should, as reported in
>> PR python/29603.
>>
>> This was happening because the watchpoint is not deleted or disabled
>> when going out of scope.
>>
>> This commit fixes this issue by disabling the watchpoint when going out
>> of scope. It also adds a test to ensure this feature isn't regressed in
>> the future.
>>
>> Calling `breakpoint_auto_delete' on all kinds of stops (in
>> `fetch_inferior_event') seem to solve this issue, but is in fact
>> inappropriate, since `breakpoint_auto_delete' goes over all breakpoints
>> instead of just going through the bpstat chain (which only contains the
>> breakpoints that were hit right now).
>>
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29603
> Hi,
>
> Hmm, re-testing the patch, it now just times out like this:
>
>      (gdb) PASS: gdb.python/py-watchpoint.exp: check modified BP count
>      continue
>      Continuing.
>      Watchpoint Hit: 1
>      FAIL: gdb.python/py-watchpoint.exp: run until program stops (timeout)
>      python print(bpt.n)
>
> It basically hangs there.  Do you see this?
>
> Simon
>