rust/tests/run-make/compiler-lookup-paths-2/b.rs

#![crate_type = "lib"]
extern crate a;
rustc: Fix a leak in dependency= paths With the addition of separate search paths to the compiler, it was intended that applications such as Cargo could require a `--extern` flag per `extern crate` directive in the source. The system can currently be subverted, however, due to the `existing_match()` logic in the crate loader. When loading crates we first attempt to match an `extern crate` directive against all previously loaded crates to avoid reading metadata twice. This "hit the cache if possible" step was erroneously leaking crates across the search path boundaries, however. For example: extern crate b; extern crate a; If `b` depends on `a`, then it will load crate `a` when the `extern crate b` directive is being processed. When the compiler reaches `extern crate a` it will use the previously loaded version no matter what. If the compiler was not invoked with `-L crate=path/to/a`, it will still succeed. This behavior is allowing `extern crate` declarations in Cargo without a corresponding declaration in the manifest of a dependency, which is considered a bug. This commit fixes this problem by keeping track of the origin search path for a crate. Crates loaded from the dependency search path are not candidates for crates which are loaded from the crate search path. As a result of this fix, this is a likely a breaking change for a number of Cargo packages. If the compiler starts informing that a crate can no longer be found, it likely means that the dependency was forgotten in your Cargo.toml. [breaking-change] 2015-01-06 16:46:07 +00:00			`#![crate_type = "lib"]`
			`extern crate a;`