Re: [PATCH 2/2] PR c++/68819: libcpp fallbacks and -Wmisleading-indentation

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Jan 06, 2016 at 03:02:05PM -0500, David Malcolm wrote:
> On Mon, 2015-12-21 at 22:20 +0100, Jakub Jelinek wrote:
> > On Mon, Dec 21, 2015 at 02:10:17PM -0700, Jeff Law wrote:
> > > On 12/18/2015 01:21 PM, David Malcolm wrote:
> > > 
> > > >I don't think there's a way to fix -Wmisleading-indentation if we're
> > > >in this state, so the first part of the following patch detects if
> > > >this has happened, and effectively turns off -Wmisleading-indentation
> > > >from that point onwards.  To avoid a false sense of security, the
> > > >patch issues a "sorry" at the that point, currently with this wording:
> > > >location-overflow-test-1.c:17:0: sorry, unimplemented: -Wmisleading-indentation is disabled from this point onwards, since column-tracking was disabled due to the size of the code/headers
> > > Seems reasonable.  I can't see any way to get indentation warnings if we
> > > don't have column info.
> > 
> > sorry will set sorrycount to non-zero though, so seen_error () will be true
> > and the compiler will exit with non-zero exit status.  That is IMHO not
> > appripriate for warning (at least unless -Werror=misleading-indentation).
> 
> Some possibilities here:
> 
> (A, the patch): issue a "sorry" to indicate that the warning isn't
> available anymore, leading to a nonzero exit status
> 
> (B) silently disable the warning
> 
> (C) issue a "warning" about the impaired warning, using
> OPT_Wmisleading_indentation, so that it becomes an error if
> -Werror=misleading-indentation.
> 
> (D) something else?
> 
> Do you have a preference as to what approach I should try?  I think I
> like option (C) above.

My preference would be inform ().  That is e.g. what var-tracking
uses in a similar case:
                  if (MAY_HAVE_DEBUG_INSNS)
                    inform (DECL_SOURCE_LOCATION (cfun->decl),
                            "variable tracking size limit exceeded with "
                            "-fvar-tracking-assignments, retrying without");
                  else
                    inform (DECL_SOURCE_LOCATION (cfun->decl),
                            "variable tracking size limit exceeded");
when the tables are too large and computing good quality debug info would be
too expensive.

	Jakub