A function was given both the ffi_const
and ffi_pure
attributes.
Erroneous code example:
#![feature(ffi_const, ffi_pure)]
extern "C" {
#[ffi_const]
#[ffi_pure] // error: `#[ffi_const]` function cannot be `#[ffi_pure]`
pub fn square(num: i32) -> i32;
}
RunAs ffi_const
provides stronger guarantees than ffi_pure
, remove the
ffi_pure
attribute:
#![feature(ffi_const)]
extern "C" {
#[ffi_const]
pub fn square(num: i32) -> i32;
}
RunYou can get more information about const
and pure
in the GCC documentation
on Common Function Attributes. The unstable Rust Book has more information
about ffi_const
and ffi_pure
.