[Bug c/68612] Const-compatibility in C

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68612

--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
I'd consider this a reasonable extension (not suitable for adding while 
trunk is in bug-fixing mode, of course) for default (non-pedantic) mode, 
similar to the extension to use C++-like rules for arrays of qualified 
type.  Similar to that, it requires a lot of care to make sure it doesn't 
cause valid code to be rejected, as well as thorough testcases.

(To be clear, the C++ rule is not symmetric between const and other 
qualifiers; it allows adding arbitrary qualifiers in certain places if 
const is present at all levels of indirection beyond those where any 
qualifiers are added.  For this purpose, in C, _Atomic should not be 
considered a qualifier, and you'd need to think about how address space 
qualifiers are involved.)