Re: PR13901

[Pedro Alves <palves at redhat dot com>]

On 04/02/2012 03:06 PM, Tristan Gingold wrote:

> 
> On Apr 2, 2012, at 3:56 PM, Pedro Alves wrote:


>> Why does GDB need to touch the shell's registers at all in the first place?
> 
> I haven't checked why.


Well, I claim that it shouldn't.  :-)  The whole existence of
fork-child.c:startup_inferior was justified on making GDB not touch the
shell.  We used to have the startup phase go through the whole
wait_for_inferior shebang, which was problematic as it touched the shell.

> 
>> If we can't skip darwin_set_sstep for all continues that are not single-steps,
>> we could at least skip those while starting up (when continuing the shell
>> until we see enough execs).  That'd suggest a new flag like
>> darwin-nat.h:struct private_inferior->starting_up, set and cleared in
>> darwin_create_inferior, and then making darwin_resume_thread do:
>>
>> -     /* Set single step.  */
>> -     inferior_debug (4, _("darwin_set_sstep (thread=%x, enable=%d)\n"),
>> -                     thread->gdb_port, step);
>> -     darwin_set_sstep (thread->gdb_port, step);
>> +     /* Avoid touching the $SHELL process, and go straight to resuming it.  */
>> +     gdb_assert (!inf->private->starting_up || !step);
>> +     if (!inf->private->starting_up)
>> +        {
>> +         /* Set single step.  */
>> +         inferior_debug (4, _("darwin_set_sstep (thread=%x, enable=%d)\n"),
>> +                         thread->gdb_port, step);
>> +         darwin_set_sstep (thread->gdb_port, step);
>>
>> WDYT?
> 
> Yes, it might be cleaner.
> 
> Honestly, I'd prefer to get rid of the shell step and directly execute the user program - or at least have an option to do that.  I think I also understand the cons of this approach.


I'd be glad to see STARTUP_WITH_SHELL turned into a run-time option.  I think there's
a PR open for that even.  However, we need the shell at least for argument globbing,
as in, e.g., debugging `ls *', so I don't think we could make it off by default,
which practically renders it an orthogonal feature.

-- 
Pedro Alves