Re: [PATCH] [RFC] Sync readline to version 6.3 patchlevel 8

[Pedro Alves <palves@redhat.com>]

Hi Patrick,

On 05/18/2015 12:41 PM, Patrick Palka wrote:

>> So the only regression appears to be
>>
>> FAIL: gdb.gdb/selftest.exp: send SIGINT signal to child process (timeout)
>>

Thanks for investigating this.  I'm looking forward to get the readline
update in.

>> What happens here is that a stopped inferior GDB is resumed using
>> "signal SIGINT" with the expectation that the parent GDB process will
>> catch this SIGINT and thus pause the inferior again.  But with
>> readline 6.3 the parent GDB process no longer catches the signal
>> raised by "signal SIGINT" and so the inferior GDB continues to run
>> until the test times out.  This seems to be caused by the fact that
>> readline 6.3 makes sure to not have its own signal handlers installed
>> when readline is not in control, whereas readline 6.2 always has its
>> signal handlers installed.  readline's signal handler basically
>> installs the applications original signal handler and then calls via
>> raise (signal).  This call to "raise (signal);" in readline's signal
>> handler is what's responsible for re-stopping the GDB inferior after
>> it was resumed with "signal SIGINT". The parent GDB process does not
>> seem to catch the first SIGINT raised by "signal SIGINT" itself
>> (regardless of what the inferior is).  

Yes, the "signal" command delivers the signal to the inferior.
The passed signal is not intercepted.

>> So without readline's signal
>> handlers installed at the point when the inferior is resumed via
>> "signal SIGINT", nothing calls "raise (signal)" later on.  The parent
>> GDB process does not catch the initial SIGINT it itself raised and
>> there is no longer subsequent SIGINT to catch because readline's
>> signal handler, which calls raise(), is no longer permanently
>> installed.
>>
>> It seems it is expected behavior that resuming an inferior via "raise
>> SIGINT" does not immediately stop the inferior giving control back to
>> GDB since interrupt.exp tests for it. 

Correct.

>> Therefore when importing
>> readline 6.3 I think we should just fix the selftest.exp test to no
>> longer expect that the inferior GDB will get stopped following "signal
>> SIGINT".  Something like:
>>

Seems reasonable to me.

Thanks,
Pedro Alves