How can Autoconf help with the transition to stricter compilation defaults?

[Paul Eggert via cfe-commits]

On 2022-11-14 04:41, Aaron Ballman wrote:
> it's generally a problem when autoconf relies on invalid
> language constructs

Autoconf *must* rely on invalid language constructs, if only to test 
whether the language constructs work. And Clang therefore must be 
careful about how it diagnoses invalid constructs. Clang shouldn't 
willy-nilly change the way it reports invalid constructs, as that can 
break Autoconf.

> issues of security
> like statically known instances of UB

It's fine to report those; I'm not saying don't report them. All I'm 
saying is that Clang should be careful about *how* it reports them.

At the very least if there are going to be changes in this area, the 
Clang developers should notify Autoconf (and presumably other) 
downstream users of the changes, and provide a supported way to get the 
old behavior for reporting, and give downstream time to adapt.