Re: Incorrect behavior in case of watchpoint

PS: Reported on bug tracker: https://bugs.kde.org/show_bug.cgi?id=384368

On Mon, Sep 4, 2017 at 5:55 PM Aetf <[email protected]> wrote:

> Hi,
>
> I can see a few issues here.
>
> 1. BreakpointModel gets updated when user creating watch points directly
> using command. The location reported by GDB includes the "-location " part,
> but since we are quoting the entire string, GDB interprets the entire
> string as an option, rather than only the "-location" part.
> 2. Even though we recognize the location and only quote remaining
> expression, GDB/MI which is the protocol we use to communicate with GDB
> actually doesn't support "-l/-location" option. see [1]
> 3. When starts new session, KDevelop tries to automatically reapply all
> break/watch points saved in BreakpointModel. But the command fails due to
> above reason. However there shouldn't be an endless loop. Once the
> command fails, it should set the error message in the Breakpoint toolview
> and continue. But maybe I'm just missing something.
>
> The fix would be
> 1. In mibreakpointcontroller.cpp:358, detect and quote only the expression
> part, this is easy.
> 2. Find a way to emulate the "-location" option. Possible solutions:
>     2.1 Take the address of the expression when watch point got set and
> save that in BreakpointModel. But addresses are likely to change between
> runs
>     2.2 Simply remove "-location" part and set it as a normal watch point.
> But likely at the very begining of the program, the expression is out of
> scope.
>     2.3 Skip it. IMHO even normal watchpoints should be skipped. As they
> rely on expressions that are hardly valid at this time.
> 3. Desired behavior should be display the error in Breakpoint toolview,
> rather than entering an endless loop. However I didn't find which part of
> the code is causing the loop after a quick of the codebase. And the desired
> behavior is already implemented. This will need more investigate.
>
> [1]
> https://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI-Breakpoint-Commands.html#GDB_002fMI-Breakpoint-Commands
>
> Cheers,
> Aetf
>
> On Mon, Sep 4, 2017 at 7:48 AM Aleix Pol <[email protected]> wrote:
>
>> On Fri, Sep 1, 2017 at 6:32 PM, Aetf <[email protected]> wrote:
>> > Hi,
>> >
>> > I'm afraid I don't have much time for this at the moment. Actually this
>> has
>> > been on my todo list for a while... I'll take a look at it soon.
>> >
>> > Cheers,
>> > Aetf
>> >
>> > On Fri, Sep 1, 2017 at 7:55 AM Aleix Pol <[email protected]> wrote:
>> >>
>> >> On Mon, Aug 21, 2017 at 1:54 PM, Aleksey Midenkov <[email protected]>
>> >> wrote:
>> >> > I've set watchpoint with command `watch -l` and it was saved in
>> >> > KDevelop session. Now it doesn't start debug session because it ends
>> >> > up in endless loop:
>> >> >
>> >> > (gdb) 2106-break-watch "-location m_part_spec.start_part"
>> >> > 2106^error,msg="-break-watch: Unknown option ``location
>> >> > m_part_spec.start_part''"
>> >> > (gdb) 2107-break-watch "-location m_part_spec.start_part"
>> >> > 2107^error,msg="-break-watch: Unknown option ``location
>> >> > m_part_spec.start_part''"
>> >> > (gdb) 2108-break-watch "-location m_part_spec.start_part"
>> >> > 2108^error,msg="-break-watch: Unknown option ``location
>> >> > m_part_spec.start_part''"
>> >> > (gdb) 2109-break-watch "-location m_part_spec.start_part"
>> >> > 2109^error,msg="-break-watch: Unknown option ``location
>> >> > m_part_spec.start_part''"
>> >> > (gdb) 2110-break-watch "-location m_part_spec.start_part"
>> >> > 2110^error,msg="-break-watch: Unknown option ``location
>> >> > m_part_spec.start_part''"
>> >> > ...
>> >> >
>> >> > Though I've managed to delete breakpoint from Breakpoints tab and
>> start
>> >> > again.
>> >>
>> >> Hey Aetf,
>> >> Any idea why that could be?
>> >>
>> >> Aleix
>> >>
>> >> PS: Aleksey, can you make sure this is reported in bugs.kde.org?
>>
>> Hi Aetf,
>> Maybe you can give us some pointers in case someone else can/wants to fix
>> it?
>>
>> Aleix
>>
>