autocfg does not work in the presence of -Z build-std about autocfg HOT 8 OPEN

Does cargo communicate this in any way? Maybe an environment variable?

from autocfg.

I've asked that question in https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/Signalling.20the.20presence.20of.20-Z.20build-std.

from autocfg.

This breaks the bigint crate for certain targets like i686-apple-darwin. Any idea for when this might be fixed?

from autocfg.

There's no plan how to fix it yet...

Assuming you mean num-bigint, it should degrade ok without it, no?

from autocfg.

Some dependent crates rely on features which get deactivated because of this, even though bigint builds successfully... I'll try to build the stdlib by hand in the meantime. Hopefully -Z build-std will be stabilized eventually.

from autocfg.

Why does autocfg care if the crate is loaded from the sysroot or passed with --extern? Shouldn't extern crate std work in both cases?

from autocfg.

Oh, is the problem that cargo only passes --extern std=... to the final crate, not to build scripts? I wonder if it should set some environment variable with a list of the std crates built from source ... in general I think it would be nice for cargo to expose a way for build scripts to invoke rustc the same way cargo would in the current build.

from autocfg.

Ah, that already exists and it's called CARGO_ENCODED_RUSTFLAGS 😄 I think we should open an upstream issue for cargo to include the --extern std flags in CARGO_ENCODED_RUSTFLAGS.

from autocfg.