add new lint [implicit_abi]

that detects external block without explicit label "C"

Signed-off-by: J-ZhengLi <lizheng135@huawei.com>

Author: J-ZhengLi

CHANGELOG.md

@@ -4580,6 +4580,7 @@ Released 2018-09-13
 [`if_then_some_else_none`]: https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none
 [`ifs_same_cond`]: https://rust-lang.github.io/rust-clippy/master/index.html#ifs_same_cond
 [`impl_trait_in_params`]: https://rust-lang.github.io/rust-clippy/master/index.html#impl_trait_in_params
+[`implicit_abi`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_abi
 [`implicit_clone`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_clone
 [`implicit_hasher`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_hasher
 [`implicit_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return

clippy_lints/src/declared_lints.rs

@@ -198,6 +198,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::if_let_mutex::IF_LET_MUTEX_INFO,
     crate::if_not_else::IF_NOT_ELSE_INFO,
     crate::if_then_some_else_none::IF_THEN_SOME_ELSE_NONE_INFO,
+    crate::implicit_abi::IMPLICIT_ABI_INFO,
     crate::implicit_hasher::IMPLICIT_HASHER_INFO,
     crate::implicit_return::IMPLICIT_RETURN_INFO,
     crate::implicit_saturating_add::IMPLICIT_SATURATING_ADD_INFO,

clippy_lints/src/implicit_abi.rs

@@ -0,0 +1,51 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use rustc_ast::ast::{Item, ItemKind};
+use rustc_errors::Applicability;
+use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks the external block without explicitly lable its ABI.
+    ///
+    /// ### Why is this bad?
+    /// Implicit ABI has negative impact on code readability.
+    ///
+    /// ### Example
+    /// ```rust
+    /// extern {
+    ///     fn c_function();
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// extern "C" {
+    ///     fn c_function();
+    /// }
+    /// ```
+    #[clippy::version = "1.70.0"]
+    pub IMPLICIT_ABI,
+    restriction,
+    "external block with implicit ABI"
+}
+
+declare_lint_pass!(ImplicitAbi => [IMPLICIT_ABI]);
+
+impl EarlyLintPass for ImplicitAbi {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
+        if let ItemKind::ForeignMod(fm) = &item.kind {
+            if fm.abi.is_none() {
+                let extern_span = cx.sess().source_map().span_until_whitespace(item.span);
+                span_lint_and_sugg(
+                    cx,
+                    IMPLICIT_ABI,
+                    extern_span,
+                    "missing ABI label on extern block",
+                    "explicitly states ABI instead",
+                    "extern \"C\"".to_string(),
+                    Applicability::MachineApplicable,
+                );
+            }
+        }
+    }
+}

clippy_lints/src/lib.rs

@@ -142,6 +142,7 @@ mod guidelines;
 mod if_let_mutex;
 mod if_not_else;
 mod if_then_some_else_none;
+mod implicit_abi;
 mod implicit_hasher;
 mod implicit_return;
 mod implicit_saturating_add;
@@ -964,6 +965,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     let mem_unsafe_functions = conf.mem_unsafe_functions.clone();
     store.register_late_pass(move |_| Box::new(guidelines::GuidelineLints::new(mem_unsafe_functions.clone())));
     store.register_late_pass(|_| Box::new(unsafe_block_in_proc_macro::UnsafeBlockInProcMacro::new()));
+    store.register_early_pass(|| Box::new(implicit_abi::ImplicitAbi));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

tests/ui/implicit_abi.fixed

@@ -0,0 +1,39 @@
+// run-rustfix
+#![allow(unused)]
+#![warn(clippy::implicit_abi)]
+
+use std::ffi::{c_char, c_void};
+
+#[repr(C)]
+pub struct External(i8);
+
+extern "C" {
+    fn foo();
+    fn bar(a: u8, b: i32) -> u64;
+    pub fn baz(a: c_char) -> c_void;
+    pub fn qux(a: External) -> c_void;
+
+    pub static a: std::ffi::c_int;
+    pub static b: External;
+    static c: i8;
+}
+
+#[rustfmt::skip]
+extern "C"
+{
+    static SOME_PTR: *mut c_void;
+}
+
+#[rustfmt::skip]
+extern "C" { fn my_c_fn(a: i8) -> c_void; }
+
+// For reference, don't lint
+extern "C" {
+    fn c_func();
+}
+// For reference, don't lint
+extern "system" {
+    pub fn system_call();
+}
+
+fn main() {}

tests/ui/implicit_abi.rs

@@ -0,0 +1,39 @@
+// run-rustfix
+#![allow(unused)]
+#![warn(clippy::implicit_abi)]
+
+use std::ffi::{c_char, c_void};
+
+#[repr(C)]
+pub struct External(i8);
+
+extern {
+    fn foo();
+    fn bar(a: u8, b: i32) -> u64;
+    pub fn baz(a: c_char) -> c_void;
+    pub fn qux(a: External) -> c_void;
+
+    pub static a: std::ffi::c_int;
+    pub static b: External;
+    static c: i8;
+}
+
+#[rustfmt::skip]
+extern
+{
+    static SOME_PTR: *mut c_void;
+}
+
+#[rustfmt::skip]
+extern { fn my_c_fn(a: i8) -> c_void; }
+
+// For reference, don't lint
+extern "C" {
+    fn c_func();
+}
+// For reference, don't lint
+extern "system" {
+    pub fn system_call();
+}
+
+fn main() {}

tests/ui/implicit_abi.stderr

@@ -0,0 +1,22 @@
+error: missing ABI label on extern block
+  --> $DIR/implicit_abi.rs:10:1
+   |
+LL | extern {
+   | ^^^^^^ help: explicitly states ABI instead: `extern "C"`
+   |
+   = note: `-D clippy::implicit-abi` implied by `-D warnings`
+
+error: missing ABI label on extern block
+  --> $DIR/implicit_abi.rs:22:1
+   |
+LL | extern
+   | ^^^^^^ help: explicitly states ABI instead: `extern "C"`
+
+error: missing ABI label on extern block
+  --> $DIR/implicit_abi.rs:28:1
+   |
+LL | extern { fn my_c_fn(a: i8) -> c_void; }
+   | ^^^^^^ help: explicitly states ABI instead: `extern "C"`
+
+error: aborting due to 3 previous errors
+