gdb remote protocol breakpoints (Z0 command)

Yao Qi
Fri Jun 20 05:41:00 GMT 2014

On 06/19/2014 10:44 PM, David Taylor wrote:
> There are many things you might want to do at a breakpoint that lack
> bytecode operators.  Just for starters,
>     . there is no bytecode operator for setting memory
>     . there is no bytecode operator for setting registers

It is fine to extend bytecode for setting memory and registers...

>     . there is no bytecode operator for calling arbitrary functions

... but calling functions is too complex to be operated by bytecode.
Each bytecode operator just does simple/primitive operation.  If we've
already had bytecode for setting memory and registers, GDB may generate
a sequence of bytecode (including setting memory and registers) to do
function call.  However, I am not very sure.

>     . there is no 'continue' option (as in: ``after performing the
>     requested commands, continue the current thread'')
> There are other capabilities that I would like as well, but without the
> four mentioned above, I don't consider it very useful at all.
> Has anyone else thought about these issuses and possibly sketched out
> extensions to allow such capabilities?
> [The 'continue' command would likely be an extension to the Z0 command,
> the others would likely be extensions to the bytecode language.]

We have a kind of breakpoint, dprintf, which is a breakpoint plus
printing and a 'continue' command at the end.  It has some flaws, but
closed to your needs.

If you don't require much interactive operations, tracepoint is a better
choice, IMO.

Yao (齐尧)

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