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.

1 files changed, 2 insertions, 2 deletions

diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
index d03c19e51f3..a167f0ffa09 100644
--- a/library/core/src/sync/atomic.rs
+++ b/library/core/src/sync/atomic.rs
@@ -809,7 +809,7 @@ impl AtomicBool {
     /// ```ignore (extern-declaration)
     /// # fn main() {
     /// use std::sync::atomic::AtomicBool;
-    /// extern {
+    /// extern "C" {
     ///     fn my_atomic_op(arg: *mut bool);
     /// }
     ///
@@ -2068,7 +2068,7 @@ macro_rules! atomic_int {
             /// # fn main() {
             #[doc = concat!($extra_feature, "use std::sync::atomic::", stringify!($atomic_type), ";")]
             ///
-            /// extern {
+            /// extern "C" {
             #[doc = concat!("    fn my_atomic_op(arg: *mut ", stringify!($int_type), ");")]
             /// }
             ///