[RFC] Use wide chars to represent Fortran source internally

[Tobias Burnus]

FX wrote:
> This patch is a first step to handling non ASCII encoded source files 
> and non-default character kinds in gfortran.
Thanks for the patch; I think supporting non-8bit characters is useful - 
especially with the move to UTF-8 and the growing importance Asian 
languages which are not representable in 8bits.

> As a consequence of this patch, memory usage to store the source file 
> roughly quadruples. I've not seen a single case where it gives a 
> significant memory increase on the total amount used during 
> compilation higher than 7%, even at -O0: for the huge 
> cp2k-in-one-file, which has 26MB, 430k-lines source files, compilation 
> at -O0 requires 1.5 GB of memory, so the 75 MB additional memory isn't 
> seen.
I think the increase is OK (as is the patch), however, I do not know 
whether anyone thinks this increase it too big.

Regarding the 100 MB (25+75 MB), I really wonder whether we could not 
release some memory while compiling. Do we really need to have that much 
in memory? For instance, do we really access lines (e.g. for error 
messages) in a module after END MODULE? Or the body of a subroutine 
after END subroutine? Actually, when are they released? I think after 
some early processing of the middle end (e.g. unused variables) the 
whole source could be thrown away, which would reduce the totally needed 
amount of memory.

Tobias,
who will do a proper review after Whit Sunday.