[clang] [compiler-rt] [Clang] Make `-Wreturn-type` default to an error in all language modes (PR #123470)

[via cfe-commits]

Sirraide wrote:

> (to me) it's not really defensible in 2025 that falling off the end of a function with a non-void return type is anything but an error.

Yeah, agreed.

> Specifically, I wonder about `autoconf`

I hadn’t thought about that, that’s a good point.

> Is that something you've looked into by any chance?

I’m not really familiar w/ autoconf, so no, I haven’t.

https://github.com/llvm/llvm-project/pull/123470