-C target-feature=+foo overrides previous values

[jbeich]

I'm trying to pass multiple -C target-feature conditionally downstream. However, despite +/- for adding/removing a feature it appears only the last value takes effect.

$ cat >a.rs
fn main() {
    if cfg!(target_feature="avx2") {
        println!("AVX2 available");
    }
    if cfg!(target_feature="fma") {
        println!("FMA available");
    }
}

$ rustc a.rs -C target-feature=+avx2 -C target-feature=+fma
$ ./a
FMA available
$ rustc a.rs -C target-feature=+avx2,+fma
$ ./a
AVX2 available
FMA available

[cuviper]

FWIW, you can check for cfg values without any test program like:

$ rustc --print cfg  -C target-feature=+avx2 -C target-feature=+fma

$ rustc --print cfg  -C target-feature=+avx2,+fma

[petrochenkov]

I agree that it's a bug and will try to fix it.

[petrochenkov]

Fixed in #72094.