E0133 - Error codes index
Description: Book listing all Rust error codes

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# Error code E0133

Unsafe code was used outside of an unsafe block.

Erroneous code example:

    unsafe fn f() { return; } // This is the unsafe code

    fn main() {
        f(); // error: call to unsafe function requires unsafe function or block
    }

Using unsafe functionality is potentially dangerous and disallowed by safety checks. Examples:

- Dereferencing raw pointers
- Calling functions via FFI
- Calling functions marked unsafe

These safety checks can be relaxed for a section of the code by wrapping the unsafe instructions with an `unsafe` block. For instance:

    unsafe fn f() { return; }

    fn main() {
        unsafe { f(); } // ok!
    }

See the unsafe section of the Book for more details.

#### Unsafe code in functions

Unsafe code is currently accepted in unsafe functions, but that is being phased out in favor of requiring unsafe blocks here too.

    #![allow(unused)]
    fn main() {
    unsafe fn f() { return; }

    unsafe fn g() {
        f(); // Is accepted, but no longer recommended
        unsafe { f(); } // Recommended way to write this
    }
    }

Linting against this is controlled via the `unsafe_op_in_unsafe_fn` lint, which is `warn` by default in the 2024 edition and `allow` by default in earlier editions.