//@ run-pass //@ ignore-windows //@ ignore-apple //@ ignore-emscripten doesn't support this linkage //@ ignore-sgx weak linkage not permitted //@ aux-build:linkage1.rs #![feature(linkage)] extern crate linkage1 as other; extern "C" { #[linkage = "extern_weak"] static foo: *const isize; #[linkage = "extern_weak"] static something_that_should_never_exist: *mut isize; } fn main() { // It appears that the --as-needed flag to linkers will not pull in a dynamic // library unless it satisfies a non weak undefined symbol. The 'other' crate // is compiled as a dynamic library where it would only be used for a // weak-symbol as part of an executable, so the dynamic library would be // discarded. By adding and calling `other::bar`, we get around this problem. other::bar(); unsafe { assert!(!foo.is_null()); assert_eq!(*foo, 3); assert!(something_that_should_never_exist.is_null()); } }