> On Jan 20, 2015, at 4:21 AM, Hafiz Abid Qadeer <hafiz_a...@mentor.com> wrote:
>
> On 16/01/15 21:53:00, Greg Clayton wrote:
>> How about:
>>
>> 2 for (int i=0; i<100; i++)
>> 3 -> printf ("i = %i\n", i); //
>> 4 printf ("this won't be executed after line 3 except for the
>> last
>> time\n");
>>
>> If you set a breakpoint on line 4 after line 3 when you will fail to
>> return to line 3 when single stepping.
>>
>> How about:
>>
>> 2 -> goto carp;
>> 3 puts("won't ever be executed");
>> 4 carp:
>> 5 puts("will get executed");
>>
>> If you set a breakpoint at line 3 you won't stop.
>>
>> Another:
>>
>> 2 -> throw foo();
>> 3 puts("this will never get hit");
>>
>> If you set a breakpoint at line 3 you will never hit it.
>>
>> Please trust that we know what we are doing when it comes to single
>> stepping. I am glad you are thinking about how things are done, but
>> just be sure think about the problem in a wider scope than "the code
>> I
>> am thinking about is linear" and think about all sorts of single
>> stepping and what you would expect to happen.
>
> In a properietary debugger that we developed in house, we spent quite a
> bit of effort on making this work mixing emulation and symbol
> information. It made a real improvements when debuggign remote
> targets using slow connections. There was always the fall back on
> stepping individual instruction when it did not work.
>
> GDB also has range stepping thing now.
> https://sourceware.org/ml/gdb-patches/2013-03/msg00450.html
That's not the same thing. That change is to have gdb send the step range to
gdbserver and then gdbserver does the single stepping till it is outside the
range. That is great when you are doing remote debugging since it reduces the
number of packets you have to send and receive. But somebody is still single
stepping.
In lldb, we don't single-step from branch to branch, we set a breakpoint on the
next branch within the range and continue. The only times lldb single-steps
are to step over breakpoints, and branches. I'm sure gdb could easily do this
trick as well, though I doubt gdbserver could. gdb does know about what
instructions do (e.g. for ARM chips without hardware single-step you have to
emulate every instruction so you can set breakpoints on the destination and run
there.) But at least last time I looked gdbserver was much lighter-weight than
this.
Jim
>
> Regards,
> Abid
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