[RFC TREE-WIDE] gcc: stop using 'int' to represent sets of qualifiers

[Joseph Myers]

On Mon, 29 Jun 2026, Martin Uecker via Gcc wrote:

> Yes, atomic as specified should not be a qualifier.  It is a mess both 
> from a standardization and also from an implementation point of view.  
> And with my "user hat" on, I can say it is also a pain because it
> prevents the use of standard atomics in many applications.

I suspect it *should* be a qualifier (that's not an access qualifier) in 
the standard - that making it such would mean fewer special cases 
referring to "atomic, qualified or unqualified" and similar than you get 
at present with it not being a qualifier but having qualifier-like 
properties regarding not being possible for rvalues.

In implementation terms, not being a qualfier would mean that everything 
that checks for a particular kind of type (e.g. POINTER_TYPE) would 
suddenly be more complicated because of needing to check for being an 
atomic type wrapper round that kind of type as well.  (We do already have 
some awkward cases like that.  For example, enumerations with fixed 
underlying type bool need checking for everywhere concerned with the 
special semantics of conversion to bool - but if atomic types were no 
longer represented as qualifiers, suddenly you get the extra complication 
that first you need to remove atomic, then move from enumeration to 
underlying type, and only then check for a boolean type.  The standard 
text has a similar issue of not having any convenient term for "integer 
type that behaves like bool" - or for that matter for signed-behavior and 
unsigned-behavior types.)

-- 
Joseph S. Myers
josmyers@redhat.com