[RFC] PR 53063 encode group options in .opt files

[Joseph S. Myers]

On Sat, 12 May 2012, Manuel López-Ibáñez wrote:

> On 11 May 2012 21:23, Joseph S. Myers <joseph@codesourcery.com> wrote:
> >
> > There's nothing wrong with having separate autogenerated functions for
> > each language if you want to split things out that way, but it would seem
> > simpler just to have one function called somewhere central, whatever
> > option it is (common or not) that is enabling other options.
> 
> The problem with this approach is that it is not clear how to decide
> in this single function that -Wextra needs to enable a C-only option
> or not. The function would need to know that it is called from the
> C-FE somehow.  Having a separate function for each language easily
> overcomes this issue.

I don't see why the function would need to know which front end it is 
called from.  If it's called from another front end, enabling a C-only 
option should be harmless (do nothing because nothing will actually check 
the gcc_options field set by the C-only option / because no handler 
actually gets called for the option)

> This is my current draft patch. It bootstraps and passes regression
> tests. It seems flexible enough to implement almost all of Wall and
> Wextra. Missing features are options that enabled by the combination
> of two options (like Wunused-parameter) and options that are
> conditional on something else (Wmain).
> 
> Is this approach ok with you? Should I clean it up and provide a changelog?

The approach is OK (even if I don't think separate functions are 
necessary, they are more modular and so logically better in that sense).  
I don't think common.opt should have LangEnabledBy listing different 
languages, though; that information should be in the front ends' .opt 
files.  And, before we add such language-specific enabling of a 
language-independent option, I'd like a good reason not to make -Wall a 
common option (also having language-specific aspects) that enables 
-Wunused for all languages - or else -Wall should (as a separate patch) be 
made to enable -Wunused for all languages, to make the semantics simpler 
and more consistent.

-- 
Joseph S. Myers
joseph@codesourcery.com