[fortran,patch] Towards wide character strings, step 2: handle characeter constants as wide strings

[FX <fxcoudert at gmail dot com>]

Hi all,

This patch goes on top of the previous "wide strings" patch, and is  
the second step in the direction of supporting non-default character  
kinds: after the first one, which made us handle all source as wide  
characters, this one makes us handle all constant character values  
internally as wide strings. Same restrictions as before apply, i.e.  
we still don't handle them throughout but instead lower them (with  
adequate checks and gcc_assert's) to usual (narrow) strings when  
emitting code for the middle-end.

This patch is rather boring. It bootstraps and regtests on x86_64- 
linux (both -m32 and -m64); no testcases are attached, as behaviour  
should not change in any case. I provide, in addition to the  
ChangeLog, two diffs: one is the "incremental" one that goes on top  
of the previous patch, and the second one is a full diff from  
mainline, that includes both patches.

OK to commit?


I think I now have a very clear view on how to go all the way to wide  
characters; we'll see if I have time to work on it, depending on  
whether I visit as many airports, planes, stations, trains and buses  
as I've done in the last 2 weeks :)  Some comments on the remaining  
issues, however, by decreasing order of difficulty (but there's  
nothing major I can see):
  -- misc assumptions in the front-end that there only is one  
character kind (all uses of char_type_node and pchar_type_node will  
have to be audited)
  -- the problem of storing wide character strings in module files:  
do we want to use encoding (UTF-8? UTF-32, and which endianness?) or  
escaping? (using \x, \u and \U)  I now favour escaping, which I think  
will really make our life easier.
  -- determining what should be done with Holleriths; I have to say  
I know virtually nothing about that, and I'd rather not learn, but I  
guess I'll have to :)
  -- handling of UTF-8 in the library; probably not too hard, as  
UTF-8 <--> UTF-32 conversion is rather simple


--
François-Xavier Coudert
http://www.homepages.ucl.ac.uk/~uccafco/

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