When do cleanups happen?

When do cleanups happen?

[Michael Snyder]

Daniel Jacobowitz wrote:
  [cleanups only happen if there is an error]
> 
> On Wed, Jan 09, 2002 at 02:18:53PM -0800, Michael Snyder wrote:
> > Cleanups are always done, no later than
> > when the command is finished executing (if not earlier).  
> 
> Well, the comments in utils.c are wrong, then :)

Hmm!  Now I am confused.

What do others think?  Are cleanups cleaned-up only on error?
Or always when a command finishes?  I know that I have found 
that if I make a cleanup that closes a file, then I cannot close
that file myself else it will wind up being closed twice.

Re: When do cleanups happen?

[Andrew Cagney]

> Daniel Jacobowitz wrote:
>   [cleanups only happen if there is an error]
> 
>> 
>> On Wed, Jan 09, 2002 at 02:18:53PM -0800, Michael Snyder wrote:
> 
>> > Cleanups are always done, no later than
>> > when the command is finished executing (if not earlier).  
> 
>> 
>> Well, the comments in utils.c are wrong, then :)
> 
> 
> Hmm!  Now I am confused.
> 
> What do others think?  Are cleanups cleaned-up only on error?
> Or always when a command finishes?  I know that I have found 
> that if I make a cleanup that closes a file, then I cannot close
> that file myself else it will wind up being closed twice.


Two styles:

	oc = make_cleanup (close, fd); // yes ok that is bad

	....blah blah

	do_cleanups (oc);

which always does the close using the cleanup.  This is kind of like a 
TRY ... FINALLY .. END construct;

	oc = make_cleanup (close, fd); // ...
	... blah blah
	discard_cleanups (oc);  //* is that the right f name?
	... blah blah
	close (fd);

which discards the cleanups so you're free to do the close.  This is 
kind of a TRY ... EXCEPT ... END.

And then there is the truth:

catch_exceptions() / catch_errors() does a cleanup.

the main command loop has a do_cleanup() call.

enjoy,
Andrew

Re: When do cleanups happen?

[Eli Zaretskii]

> Date: Wed, 09 Jan 2002 19:36:36 -0500
> From: Andrew Cagney <ac131313@cygnus.com>
> > 
> > Hmm!  Now I am confused.
> > 
> > What do others think?  Are cleanups cleaned-up only on error?
> > Or always when a command finishes?  I know that I have found 
> > that if I make a cleanup that closes a file, then I cannot close
> > that file myself else it will wind up being closed twice.
> 
> Two styles:

Andrew, if Michael got confused by this, our docs needs work.  So I
suggest to add the nice explanations below to gdbint.texinfo, as the
first step towards a remedy.  There's a section about cleanups there
where these explanations will fit nicely.

> 	oc = make_cleanup (close, fd); // yes ok that is bad
> 
> 	....blah blah
> 
> 	do_cleanups (oc);
> 
> which always does the close using the cleanup.  This is kind of like a 
> TRY ... FINALLY .. END construct;
> 
> 	oc = make_cleanup (close, fd); // ...
> 	... blah blah
> 	discard_cleanups (oc);  //* is that the right f name?
> 	... blah blah
> 	close (fd);
> 
> which discards the cleanups so you're free to do the close.  This is 
> kind of a TRY ... EXCEPT ... END.
> 
> And then there is the truth:
> 
> catch_exceptions() / catch_errors() does a cleanup.
> 
> the main command loop has a do_cleanup() call.
> 
> enjoy,
> Andrew
> 
> 
> 
> 
> 
> 

Re: When do cleanups happen?

[Andrew Cagney]

> 
> Andrew, if Michael got confused by this, our docs needs work.  So I
> suggest to add the nice explanations below to gdbint.texinfo, as the
> first step towards a remedy.  There's a section about cleanups there
> where these explanations will fit nicely.


Yes (and thanks).

Andrew