[Bug target/17211] [sparc/i386]: Bitfields should be *unsigned* by default.

["jsm at polyomino dot org dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From jsm at polyomino dot org dot uk  2004-08-27 17:03 -------
Subject: Re:  [sparc/i386]: Bitfields should be *unsigned*
 by default.

On Fri, 27 Aug 2004, terra at gnome dot org wrote:

> C99 only requires bitfields of base types _Bool, enums, int, signed int, and
> unsigned int.  No char, no short, and no long long -- they are left to the
> implementation.

C99 says "or some other implementation-defined type".

At present we support no such types; see implement-c.texi.  Attempts to 
use such types get pedwarns with -pedantic.

Suppose we were to support short as such a type.  6.7.2#5 says that short, 
signed short, short int and signed short int all designate the same type.  
It has an exception for int as a bit-field type, but none for short.  
Thus if an implementation supports short bit-fields as an 
implementation-defined bit-field type, they must be the same as signed 
short bit-fields.  This may be a defect, but it is the clear meaning of 
the standard is it is at present.

I don't think we should change to supporting such types as 
implementation-defined bit-field types without a DR on this, and another 
DR on the meaning of sizeof applied to an expression derived by arithmetic 
on bit-field types wider than int.



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17211