Re: PATCH: Re: Odd trap return status

[Peter Stephenson <pws@csr.com>]

Bart Schaefer wrote:
> On Wed, 29 May 2002, Peter Stephenson wrote:
> 
> > We save and restore a whole load of status for all traps, which isn't
> > necessary if they are fake traps which are never caused by signals.
> > This is a minimal patch for that.
> 
> Hrm.  This seems wrong to me.  TRAPDEBUG definitely MUST NOT affect the
> return code, etc., of the surrounding function.
> 
> It would seem to me that even TRAPEXIT should not change values such as
> list_pipe_job and badcshglob.

I think you may be missing the point a bit, unless I am...

  trap 'return 1' DEBUG

would already cause a return from the enclosing function, only the
return status would get lost.  I haven't changed the command flow at
all, only the effect on status variables.  So it seems to me illogical
to insist that the return value be lost.  (However, you can argue that
applies to traps from real signals, too.)

The other stuff --- list_pipe_job, etc. --- should be maintained
consistently anyway.  The point about saving it was not because the
function shouldn't affect the surroundings --- if it was, we would need
to do it in a whole load of other cases such as precmd --- but because
the signal could happen at a point where the shell was already in the
middle of executing something else, and this could cause an inconsistent
state which we needed to recover from.

I think.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 392070


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