Static variables with the #[linkage]
attribute within external blocks must have one of the following types, which are equivalent to a nullable pointer in C:
*mut T
or *const T
, where T
may be any type.
An enumerator type with no #[repr]
attribute and with two variants, where one of the variants has no fields, and the other has a single field of one of the following non-nullable types:
The variants can appear in either order.
For example, the following declaration is invalid:
#![feature(linkage)] extern "C" { #[linkage = "extern_weak"] static foo: i8; }
The following declarations are valid:
#![feature(linkage)] extern "C" { #[linkage = "extern_weak"] static foo: Option<unsafe extern "C" fn()>; #[linkage = "extern_weak"] static bar: Option<&'static i8>; #[linkage = "extern_weak"] static baz: *mut i8; }