Auto merge of #76219 - Mark-Simulacrum:extern-require-abi, r=estebank

Add allow-by-default lint on implicit ABI in extern function pointers and items

This adds a new lint, missing_abi, which lints on omitted ABIs on extern blocks, function declarations, and function pointers.

It is currently not emitting the best possible diagnostics -- we need to track the span of "extern" at least or do some heuristic searching based on the available spans -- but seems good enough for an initial pass than can be expanded in future PRs.

This is a pretty large PR, but mostly due to updating a large number of tests to include ABIs; I can split that into a separate PR if it would be helpful, but test updates are already in dedicated commits.

3 files changed, 9 insertions, 9 deletions

diff --git a/library/std/src/ffi/c_str.rs b/library/std/src/ffi/c_str.rs
index 60b642a6dba..230ef0b23db 100644
--- a/library/std/src/ffi/c_str.rs
+++ b/library/std/src/ffi/c_str.rs
@@ -86,7 +86,7 @@ use crate::sys;
 /// use std::ffi::CString;
 /// use std::os::raw::c_char;
 ///
-/// extern {
+/// extern "C" {
 ///     fn my_printer(s: *const c_char);
 /// }
 ///
@@ -144,7 +144,7 @@ pub struct CString {
 /// use std::ffi::CStr;
 /// use std::os::raw::c_char;
 ///
-/// extern { fn my_string() -> *const c_char; }
+/// extern "C" { fn my_string() -> *const c_char; }
 ///
 /// unsafe {
 ///     let slice = CStr::from_ptr(my_string());
@@ -159,7 +159,7 @@ pub struct CString {
 /// use std::os::raw::c_char;
 ///
 /// fn work(data: &CStr) {
-///     extern { fn work_with(data: *const c_char); }
+///     extern "C" { fn work_with(data: *const c_char); }
 ///
 ///     unsafe { work_with(data.as_ptr()) }
 /// }
@@ -174,7 +174,7 @@ pub struct CString {
 /// use std::ffi::CStr;
 /// use std::os::raw::c_char;
 ///
-/// extern { fn my_string() -> *const c_char; }
+/// extern "C" { fn my_string() -> *const c_char; }
 ///
 /// fn my_string_safe() -> String {
 ///     unsafe {
@@ -359,7 +359,7 @@ impl CString {
     /// use std::ffi::CString;
     /// use std::os::raw::c_char;
     ///
-    /// extern { fn puts(s: *const c_char); }
+    /// extern "C" { fn puts(s: *const c_char); }
     ///
     /// let to_print = CString::new("Hello!").expect("CString::new failed");
     /// unsafe {
@@ -465,7 +465,7 @@ impl CString {
     /// use std::ffi::CString;
     /// use std::os::raw::c_char;
     ///
-    /// extern {
+    /// extern "C" {
     ///     fn some_extern_function(s: *mut c_char);
     /// }
     ///
@@ -1147,7 +1147,7 @@ impl CStr {
     /// use std::ffi::CStr;
     /// use std::os::raw::c_char;
     ///
-    /// extern {
+    /// extern "C" {
     ///     fn my_string() -> *const c_char;
     /// }
     ///
diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs
index 417a54e9dff..6b06539a094 100644
--- a/library/std/src/keyword_docs.rs
+++ b/library/std/src/keyword_docs.rs
@@ -401,7 +401,7 @@ mod enum_keyword {}
 ///
 /// ```rust
 /// #[no_mangle]
-/// pub extern fn callable_from_c(x: i32) -> bool {
+/// pub extern "C" fn callable_from_c(x: i32) -> bool {
 ///     x % 3 == 0
 /// }
 /// ```
diff --git a/library/std/src/sys/unix/weak.rs b/library/std/src/sys/unix/weak.rs
index e93a4972caa..432fe4c33bc 100644
--- a/library/std/src/sys/unix/weak.rs
+++ b/library/std/src/sys/unix/weak.rs
@@ -28,7 +28,7 @@ use crate::sync::atomic::{self, AtomicUsize, Ordering};
 
 macro_rules! weak {
     (fn $name:ident($($t:ty),*) -> $ret:ty) => (
-        static $name: crate::sys::weak::Weak<unsafe extern fn($($t),*) -> $ret> =
+        static $name: crate::sys::weak::Weak<unsafe extern "C" fn($($t),*) -> $ret> =
             crate::sys::weak::Weak::new(concat!(stringify!($name), '\0'));
     )
 }