Re: broken FE diagnostics wrt complex expressions

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Wed, 13 Aug 2008, Aldy Hernandez wrote:

> It seems to me that the only approach here would be to provide caret
> diagnostics, because reconstructing the original sources from GENERIC
> seems like a loosing proposition.  

In some cases the only useful place to find the expression is in the 
preprocessed sources, not the original sources, so you want to be able to 
print an expression extracted from those not just one extracted from 
pointers into the original sources.  But in either case extracting an 
expressions using some form of beginning and ending locations would give 
better results than reconstructing a representation of the expression from 
trees.

(This would involve keeping two locations for an expression rather than 
one, but an opaque location_t cookie ought to be able to represent 
locations in both original and preprocessed source so you shouldn't need 
four locations.)

> But, is this slew of work even worth it?  I for one think that the
> aforementioned PRs should at least be marked down considerably.  3 of
> them are P2s-- and I think they should be some Pn+5, and/or mark them as
> an enhancement request.

I set 35441 to P4, and Volker complained that it should have been P2 
(though he didn't take me up on my invitation to reset it to P3 for 
another RM to look at it).

I think it would certainly be reasonable to print <complex expression> for 
anything unsupported instead of broken diagnostics, and to reclassify all 
such bugs as wishlist requests for certain complex expressions to be 
better supported in diagnostics.

-- 
Joseph S. Myers
joseph@codesourcery.com