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foreign function interface

The way code in one language calls functions written in another.

Rust's FFI declares foreign functions in extern blocks and exports Rust functions with extern "C" signatures, communicating through C-compatible types.

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Examples

  • unsafe extern "C" { fn strlen(text: *const c_char) -> usize; } declares a C function; in edition 2024 a bare extern "C" { ... } fails with extern blocks must be unsafe.

See also

ABI raw pointer opaque handle name mangling
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