Result location semantics with a buffer inside a labeled block

[matklad]

@vulpesx

But the intended language semantics is the opposite

Hm, I’ve heard that the intended language semantics is that local variables are live until the end of enclosing function/loop

Lifetime of temporaries

I was also interested on knowing this and I got an answer on the zig discord and this code is correct for now and will likely be formalized as defined behavior. referenced rvalues (temporaries) live until the end of the function, or until the end of the innermost loop they were in

This makes sense to me:

• Extending the lifetime prevents bugs and simplifies the code.
• The optimizer should be capable of precisely tracking what is actually used and what’s not. Even with C/C++ rules, there is going to be liveness analysis in the optimization pipeline, so it’s not like the surface language-level rule changes much in the resulting code.

This is actually one of the smaller happy consequences of abandoning RAII: with RAII, you are forced to language lawyer when exactly drop happens, with a tone of finicky rules (e.g. if let temporary scope - The Rust Edition Guide). With defer, you have very explicit syntax for where side-effects happen, and the stack memory can have “whatever” lifetime.