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Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0757.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0757.md | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0757.md b/compiler/rustc_error_codes/src/error_codes/E0757.md new file mode 100644 index 000000000..41b06b23c --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0757.md @@ -0,0 +1,33 @@ +A function was given both the `ffi_const` and `ffi_pure` attributes. + +Erroneous code example: + +```compile_fail,E0757 +#![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; +} +``` + +As `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; +} +``` + +You 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`]. + +[GCC documentation on Common Function Attributes]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html +[`ffi_const`]: https://doc.rust-lang.org/nightly/unstable-book/language-features/ffi-const.html +[`ffi_pure`]: https://doc.rust-lang.org/nightly/unstable-book/language-features/ffi-pure.html |