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Move naked function ABI check to its own lint

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This check was previously categorized under the lint named
`UNSUPPORTED_NAKED_FUNCTIONS`. That lint is future incompatible and will
be turned into an error in a future release. However, as defined in the
Constrained Naked Functions RFC, this check should only be a warning.
This is because it is possible for a naked function to be implemented in
such a way that it does not break even the undefined ABI. For example, a
`jmp` to a `const`.

Therefore, this patch defines a new lint named
`UNDEFINED_NAKED_FUNCTION_ABI` which contains just this single check.
Unlike `UNSUPPORTED_NAKED_FUNCTIONS`, `UNDEFINED_NAKED_FUNCTION_ABI`
will not be converted to an error in the future.

rust-lang/rfcs#2774
rust-lang/rfcs#2972
This commit is contained in:
Nathaniel McCallum 2021-08-04 15:00:49 -04:00
parent 6fe0886723
commit ba9afb58b3
4 changed files with 43 additions and 16 deletions
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34
compiler/rustc_lint_defs/src/builtin.rs
View file

@ -2691,6 +2691,38 @@ declare_lint! {
"detects deprecation attributes with no effect",
}
declare_lint! {
/// The `undefined_naked_function_abi` lint detects naked function definitions that
/// either do not specify an ABI or specify the Rust ABI.
///
/// ### Example
///
/// ```rust
/// #![feature(naked_functions)]
/// #![feature(asm)]
///
/// #[naked]
/// pub fn default_abi() -> u32 {
/// unsafe { asm!("", options(noreturn)); }
/// }
///
/// #[naked]
/// pub extern "Rust" fn rust_abi() -> u32 {
/// unsafe { asm!("", options(noreturn)); }
/// }
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The Rust ABI is currently undefined. Therefore, naked functions should
/// specify a non-Rust ABI.
pub UNDEFINED_NAKED_FUNCTION_ABI,
Warn,
"undefined naked function ABI"
}
declare_lint! {
/// The `unsupported_naked_functions` lint detects naked function
/// definitions that are unsupported but were previously accepted.
@ -2701,7 +2733,7 @@ declare_lint! {
/// #![feature(naked_functions)]
///
/// #[naked]
/// pub fn f() -> u32 {
/// pub extern "sysv64" fn f() -> u32 {
/// 42
/// }
/// ```