[fortran,patch] Creating a common header to the front-end and runtime library

[Tobias Schlüter]

François-Xavier Coudert wrote:
>> I see that you haven't added Makefile rules for the dependency.
> 
> Very good point. For the front-end, they need to be added to
> Make-lang.in (everywhere gfortran.h is), and I guess for the library
> they are automagically handled, aren't they?

Yes, but I am wondering if cross-directory dependencies work.

>>  With my supposed change you could do without
>> cross-directory dependencies (just rebuild the library everytime the
>> compiler changes), but this is far from optimal.
> 
> I think the right answer is beyond what a dependency system can do.
> When you change the compiler, only you know whether it will affect
> code-generation in a way that will matter for libgfortran. Since very
> few changes actually affect the building of libgfortran, I suggest
> that we keep the current system (no dependency; if you know you
> changed something that requires rebuilding libgfortran, delete that
> directory) except for adding dependency on the common header. How does
> that sound?

That's probably the best we can get.

>> One alternative approach that I could think of is having a compiler flag
>> that allows the compiler to dump a header file for the library.  Then,
>> while building the library you do
>>   gfortran --dump-compatibility-stuff > include/libgfortran_fe.h
>>
>> This wouldn't solve the dependency issues, though.
> 
> Too heavy for this particular task, I think.

Completely agreed.

Cheers,
- Tobi