Cargo concatenates rustflags from .cargo/configss in reversed order #8128
Description
Consider this setup:
outer
├── .cargo
│ └── config
└── inner
├── .cargo
│ └── config
├── Cargo.toml
└── src
└── main.rs
Less specific outer/.cargo/config contains
[build]
rustflags = ["-Ccodegen-units=1"]More specific outer/inner/.cargo/config contains
[build]
rustflags = ["-Ccodegen-units=2"]The compiler's command line in this case is
rustc --crate-name inner --edition=2018 'src\main.rs' ... -Ccodegen-units=2 -Ccodegen-units=1rustc like many other tools prefers the last specified value for the given option to support hierarchical build systems.
With Cargo's flag concatenation behavior this means that less specific flags override more specific flags, which is not a correct behavior.