Re: [PATCH] Always print "Detaching after fork from child..."

[Sergio Durigan Junior <sergiodj at redhat dot com>]

On Thursday, January 25 2018, Pedro Alves wrote:

> On 01/24/2018 08:56 PM, Sergio Durigan Junior wrote:
>> On Wednesday, January 24 2018, Jan Kratochvil wrote:
>> 
>>> On Wed, 24 Jan 2018 20:47:14 +0100, Sergio Durigan Junior wrote:
>>>>   https://bugzilla.redhat.com/show_bug.cgi?id=235197
>>>
>>> As a justification for this patch:
>>>
>>> ------------------------------------------------------------------------------
>>> cat >fork2.c <<EOH
>>> #include <unistd.h>
>>> #include <stdio.h>
>>> static void printit(void) {
>>>   puts("printed");
>>> }
>>> int main(void) {
>>>   if (!fork()) printit();
>>>   return 0;
>>> }
>>> EOH
>>> gcc -o fork2 fork2.c -Wall -g
>>> gdb -q ./fork2
>>> (gdb) b printit
>>> Breakpoint 1 at 0x40052b: file fork2.c, line 4.
>>> (gdb) r
>>> Starting program: /quad/home/jkratoch/t/fork2 
>>> printed
>>> [Inferior 1 (process 15812) exited normally]
>>> (gdb) q
>>> ------------------------------------------------------------------------------
>>>
>>> As the GDB user does not expect the program could do any forks s/he is
>>> confused the breakpoint did not get hit and assumes GDB is just broken.
>> 
>> Thanks for the extra justification and the useful example.
>> 
>>> But then I cannot say this patch is too great, it produces many uninteresting 
>>> 	Detaching after fork from child process 24905.
>>> messages rather just annoying in most cases.  So nowadays I feel the message
>>> is more an excuse how to show it is user's fault s/he did not read it.
>>> But I think nobody reads them as there are too many such messages.
>> 
>> I understand where you're coming from, but I still think this is a good
>> patch because I read the messages, and as I said, they even helped me in
>> one occasion.
>
> I'm of two minds here.  On the one hand, "help, GDB doesn't stop at
> my breakpoint!" is a FAQ on IRC.  OTOH, I also worry a bit about
> printing too many messages.
>
> Maybe the middle ground is having a way to toggle this output on/off
> other than the over-broad "set verbose".  An idea would be to make it
> conditional on the existing "set print inferior-events" instead, and
> flip "set print inferior-events" on by default, like
> "set print thread-events" is on by default.  One trouble with the
> "set print inferior-events" setting is that currently it prints
> redundant info, like:
>
>  ~~
>  [Inferior 1 (process 2629) exited normally]
>  [Inferior 2629 exited]
>  ~~
>
> But we can fix that, I think.  See a quick straw-man patch below.
> (Really just a a straw-man; there's more redundancy if you do "follow-fork child",
> for example.)

Thanks for the reply and the patch.  It is my understanding that you
would like it to be extended in order to avoid redundancy in other
cases.  I will take a look at it.

-- 
Sergio
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