Re: libstdc++ vs. -fshow-column

[Aldy Hernandez <aldyh at redhat dot com>]

On Thu, Jun 11, 2009 at 11:17:11AM -0700, Benjamin Kosnik wrote:
> 
> Hey y'all:
> 
> > The libstdc++ testsuite doesn't use the overrides for dg-error et al.
> > I believe Janis is looking into this.
> 
> Thanks for the workaround on this Aldy. 
> 
> Is there any way I can get more detail on the "dg-error overrides"
> problem? Not quite sure what you mean here, or what it is that should be
> done. Any pointers appreciated.

Janis-- please correct me if I'm wrong.

The default dg-{error,warning,etc} procedures in dejagnu are currently
overloaded in the C and C++ dg.exp machinery to handle columns.  I
believe Janis did this because it was easier to do this, than to require
GCC to use a newer version of dejagnu (and get our patches into
dejagnu).

GCC now defaults to -fshow-column, but stock dejagnu does not handle
columns gracefully.  It gets confused if a column number matches a line
number that you want to match.  There are thre possible solutions for
the libstdc++ testsuite:

	a) Override the libstdc++ harness like we're currently doing for
	   C and C++ dg.exp.
	b) Modify any tests affected to match the actual column.
	c) Make the libstdc++ testsuite harness pass -fshow-column.

We need to do (a) sooner or later, and ideally (b) as well as we become
more comfortable with the C++ front-end emitting correct column
information.  Approach (c) is just papering over the problem.

Aldy