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

[Paul Eggert via cfe-commits]

On 2022-11-15 06:50, Jonathan Wakely wrote:
> Could you clarify what you mean, with a concrete example? Surely as
> long as errors are reported on stderr and the compiler exits with
> non-zero status, that's an acceptable way to report errors?

Not if the "error" is harmless as far as Autoconf is concerned, which is 
what led to this thread. The concrete example here is that Autoconf 
needs to check whether a function can be linked to (as opposed to 
checking the function's signature). Clang shouldn't get in the way.

In lots of places the C standard says behavior is undefined, even though 
the behavior is fine on the current platform for the intended use. It's 
not just the example we're talking about; adding zero to a null pointer 
is another such example.

In such cases it's OK for Clang to warn, but having Clang exit with 
nonzero status is overkill and counterproductive.