Re: [PATCH] stepi/nexti: skip signal handler if "handle nostop" signal arrives

[Pedro Alves <palves@redhat.com>]

On 10/14/2014 07:27 PM, Eli Zaretskii wrote:
>> From: Pedro Alves <palves@redhat.com>
>> Date: Tue, 14 Oct 2014 18:48:30 +0100
>>
>> --- a/gdb/doc/gdb.texinfo
>> +++ b/gdb/doc/gdb.texinfo
>> @@ -5526,6 +5526,11 @@ Their full names are:
>>  @value{GDBN} should not stop your program when this signal happens.  It may
>>  still print a message telling you that the signal has come in.
>>  
>> +If this signal arrives while a stepping command (e.g., @code{step}) is
>> +in progress, the signal's handler is skipped (though still executed if
>> +@code{pass} is in effect; see below).  @value{GDBN} will still stop
>> +your program if the handler hits a breakpoint.
> 
> This description is confusing.  For starters, it only mentions some of
> the possible setting of signal handling, and keeps silence about the
> rest.  Either we should describe what happens with all of them, one by
> one, or (better) says something that will explain how we handle them
> all, at once.

This paragraph is added to the "nostop" entry of the table.  It directly
relates to the entry in question:

Specifically, it's a preemptive response to the question I'd have if
I read the paragraph just above, which talks about the signal but
leaves the question of the signal handler open:

 @table @code
 @item nostop
 @value{GDBN} should not stop your program when this signal happens.  It may
 still print a message telling you that the signal has come in.

 If this signal arrives while a stepping command (e.g., @code{step}) is
 in progress, the signal's handler is skipped (though still executed if
 @code{pass} is in effect; see below).  @value{GDBN} will still stop
 your program if the handler hits a breakpoint.

I could extend the "stop" item:

 @item stop
 @value{GDBN} should stop your program when this signal happens.  This implies
 the @code{print} keyword as well.

Like:

+ The signal is not visible to the program until you continue.

WDYT?


This is also said further below, after the table (and is what the
"see below" referred to):

  When a signal stops your program, the signal is not visible to the
  program until you
  continue.  Your program sees the signal then, if @code{pass} is in
  effect for the signal in question @emph{at that time}.  In other words,
  after @value{GDBN} reports a signal, you can use the @code{handle}
  command with @code{pass} or @code{nopass} to control whether your
  program sees that signal when you continue.

 +If a stepping command is issued after the program stops for a signal,
 +and @code{pass} is in effect for that signal, @value{GDBN} steps into
 +the signal's handler (if the target supports it).

The '+' lines are what I'm adding.
> 
> Also, I believe the description of stepping should mention this
> aspect, with a cross-reference to here.

OK.

> 
>> +If a stepping command is issued after the program stops for a signal,
>> +and @code{pass} is in effect for that signal, @value{GDBN} steps into
>> +the signal's handler (if the target supports it).
> 
> Again, this left me wondering.  E.g., if the program stops for a
> signal, then we are already in the signal handler, no?

No, we intercept the signal before the program sees it.  See above.

> So the fact
> that stepping commands continue there is a no-brainer, right?  Or a I
> again confused?

The latter.  :-)

Thanks,
Pedro Alves