Re: [Qemu-devel] [RFC 00/15] Error API: Flag errors in *errp even if errors are being ignored

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jun 28, 2017 at 11:05:26AM +0200, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
> > Rationale
> > ---------
> >
> > I'm often bothered by the fact that we can't write the following:
> >
> >     foo(arg, errp);
> >     if (*errp) {
> >         handle the error...
> >         error_propagate(errp, err);
> >     }
> >
> > because errp can be NULL.
> 
> If foo() additionally returned an indication of success, you could write
> 
>       if (!foo(arg, errp)) {    // assuming foo() returns a bool
>           handle the error...
>       }
> 
> Nicely concise.
> 
> For what it's worth, this is how GLib wants GError to be used.  We
> deviated from it, and it has turned out to be a self-inflicted wound.

FWIW, I took that approach for the io & crypto layers - except
returning 0 vs -1, rather than true/false, precisely because
it lead to simpler code by not having to use local errors and
propagation.

For added benefit you can potentially then also annotate the
method as  __attribute__(return_check)  to force the caller
to include a check for error conditions, which is often a
useful compile time protection to have.

Regards,
Daniel
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