Re: GDB process (on Linux) cooperating with the debugged process (some particular pthread on it)

[Andrew Burgess via Gdb <gdb@sourceware.org>]

Basile Starynkevitch <basile@starynkevitch.net> writes:

> On Thu, 2025-05-15 at 12:04 +0100, Andrew Burgess via Gdb wrote:
>> Basile Starynkevitch <basile@starynkevitch.net> writes:
>> 
>> > Hello all,
>> > 
>> > Is it possible for the debugged process (for me the RefPerSys inference
>> > engine,
>> > GPL licensed, see below) which has several threads to send GDB commands or
>> > interact with the debugger process.
>> 
>> I'm not aware of any existing, general technique for having the debuggee
>> send commands to the debugger.  There is some limited support for JIT
>> like processes to allow the process to give GDB debug information for
>> the dynamically generated code, but nothing beyond that.
>
> Thanks. Do you mind explaining how that works? or in what GDB source files does
> that happen?

Start by reading:

 https://sourceware.org/gdb/current/onlinedocs/gdb.html/JIT-Interface.html#JIT-Interface

Though the documentation isn't great, I think it could be improved with
some examples maybe.  But you can find some example code in the
testsuite, look in gdb/testsuite/gdb.base/ and read through any of the
files starting with 'jit-'.

In GDB source the entry point for jit handling is in jit.c, but if your
interest is being a user then hopefully the docs should be enough.

Thanks,
Andrew