Re: [PATCH] Fix mi-detach.exp on native-gdbserver

[Pedro Alves <palves at redhat dot com>]

On 09/11/2015 07:11 PM, Simon Marchi wrote:
> On 15-09-09 05:39 AM, Pedro Alves wrote:
>> Please try enabling "set print inferior-events on".  With native
>> debugging, we currently get:
>>
>>  (gdb) detach
>>  Detaching from program: /home/pedro/gdb/tests/main, process 15759
>>  [Inferior 15759 detached]
>>                  ^^^^^^^^
>>
>> However, with target extended-remote, we get:
>>
>>  (gdb) tar extended-remote :9999
>>  (gdb) detach
>>  Detaching from program: /home/pedro/gdb/tests/main, process 15789
>>  [Inferior 15789 exited]
>>                  ^^^^^^
>>
>> And with target remote, we get nothing:
>>
>>  (gdb) tar remote :9999
>>  0x0000003615a011f0 in _start () from target:/lib64/ld-linux-x86-64.so.2
>>  (gdb) detach
>>  Detaching from program: /home/pedro/gdb/tests/main, process 15767
>>  Ending remote debugging.
>>  (gdb)
>>
>> With your patch, we'll print "exited" in the remote case too,
>> when it seems to me that in both extended-remote and remote
>> we should be saying "detached" like in the native case.
>>
>> Also, if the user does "disconnect", after your patch gdb will
>> say the inferiors we were debugging "exited" while they were
>> left running on the target side.  Is that confusing?
>>
>> Thanks,
>> Pedro Alves
> 
> The fact that different targets have different behaviors is certainly confusing
> and I think it should be improved.
> 
> The problem seems to be that remote_mourn and extended_remote_mourn don't have
> enough information as to why they are mourning an inferior, so they just end up
> calling exit_inferior.  In the native case, the message is right because
> inf_ptrace_detach calls directly detach_inferior (which is exactly like
> exit_inferior, except the message).  

remote_detach_1 also calls detach_inferior, though the condition
there looks a bit confusing.

> By the way, it means that when detaching
> natively, we never mourn the inferior, is it normal?.

I think most targets _don't_ mourn when detaching.  Maybe we could/should
make them all do so, not sure.  E.g., looking at generic_mourn_inferior, we
shouldn't need to mark breakpoints out when detaching, as we better have
really removed breakpoints from the inferior before we detached it.
Maybe we should instead have a generic_detach_inferior function.  That
also avoids the "why are we mourning the living?" question too.  :-)

Thanks,
Pedro Alves

> 
> According to these backtraces, it seems like it would be possible for the "mourn"
> functions to take a "why are we mourning" argument, so that the message printed there
> can be adjusted.
> 
> #0  remote_mourn (target=0x2136200 <remote_ops>) at /home/emaisin/src/binutils-gdb/gdb/remote.c:8502
> #1  0x00000000007fb350 in delegate_mourn_inferior (self=0x2136200 <remote_ops>) at /home/emaisin/src/binutils-gdb/gdb/target-delegates.c:1285
> #2  0x0000000000808b3e in target_mourn_inferior () at /home/emaisin/src/binutils-gdb/gdb/target.c:2317
> #3  0x000000000064b2f2 in remote_detach_1 (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/remote.c:4723
> #4  0x000000000064b353 in remote_detach (ops=0x2136200 <remote_ops>, args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/remote.c:4734
> #5  0x00000000007f747d in delegate_detach (self=0x2136200 <remote_ops>, arg1=0x0, arg2=1) at /home/emaisin/src/binutils-gdb/gdb/target-delegates.c:34
> #6  0x0000000000808888 in target_detach (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/target.c:2216
> #7  0x00000000007a4677 in detach_command (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/infcmd.c:2908
> 
> #0  extended_remote_mourn (target=0x2136780 <extended_remote_ops>) at /home/emaisin/src/binutils-gdb/gdb/remote.c:8511
> #1  0x00000000007fb2a8 in delegate_mourn_inferior (self=0x2136780 <extended_remote_ops>) at /home/emaisin/src/binutils-gdb/gdb/target-delegates.c:1285
> #2  0x0000000000808a7f in target_mourn_inferior () at /home/emaisin/src/binutils-gdb/gdb/target.c:2317
> #3  0x000000000064b27b in remote_detach_1 (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/remote.c:4723
> #4  0x000000000064b302 in extended_remote_detach (ops=0x2136780 <extended_remote_ops>, args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/remote.c:4740
> #5  0x00000000007f73dd in delegate_detach (self=0x2136780 <extended_remote_ops>, arg1=0x0, arg2=1) at /home/emaisin/src/binutils-gdb/gdb/target-delegates.c:34
> #6  0x00000000008087d8 in target_detach (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/target.c:2216
> #7  0x00000000007a45e1 in detach_command (args=0x0, from_tty=1) at /home/emaisin/src/binutils-gdb/gdb/infcmd.c:2908
> 
> Does it make sense?
> 

Seems like one of those "have to try to tell" cases.