Re: C/C++ PATCH to add __typeof_noqual (PR c/65455, c/39985)

[Joseph Myers <joseph at codesourcery dot com>]

On Wed, 28 Jun 2017, Martin Sebor wrote:

> > I.e., just having blocks to remove qualifiers of kind X is not sufficient
> > without "remove all qualifiers (possibly except these kinds)" as well.  I
> > suppose you could have __remove_quals (const volatile _Atomic, expr) and
> > __remove_quals_except (_Atomic, expr) or similar (with some keyword that
> > goes in there to mean "any address space").
> 
> Right.  My point isn't that the bigger features shouldn't exist,
> but that they can and should be built on top of the primitives
> and defined not in the compiler but in a header.  With
> __bultin_remove_const() and __builtin_remove_volatile()
> a __typeof_noqual(x) can be a macro that expands to these two,
> plus any others as/if necessary, with any other additional

My point is that users should not need to update their definitions every 
time another qualifier is invented.  Either you need the "remove 
qualifiers except" functionality in the language, or you need a 
*compiler-provided* header that defines "remove qualifiers except" 
operations for every combination of qualifiers in that version of the 
compiler (because "remove qualifiers except _Atomic" and "remove 
qualifiers except address spaces" cannot be composed into "remove 
qualifiers except _Atomic and address spaces, and "remove const, volatile, 
restrict and address spaces" is not something user code should need to 
hardcode when the intent is "remove qualifiers except _Atomic").

> adjustments, again if/when necessary.  This is the C++ approach;

C++ doesn't seem to add new qualifiers so much.

-- 
Joseph S. Myers
joseph@codesourcery.com