Add a ChangeLog entry for SE-0458

Author: DougGregor

CHANGELOG.md

@@ -3,6 +3,31 @@
 > [!NOTE]
 > This is in reverse chronological order, so newer entries are added to the top.
 
+## Swift 6.2
+
+* [SE-0458][]:
+  Introduced an opt-in mode for strict checking of memory safety, which can be
+  enabled with the compiler flag `-strict-memory-safety`. In this mode,
+  the Swift compiler will produce warnings for uses of memory-unsafe constructs
+  and APIs. For example, 
+
+  ```swift
+  func evilMalloc(size: Int) -> Int {
+    // warning: call to global function 'malloc' involves unsafe type 'UnsafeMutableRawPointer'
+    return Int(bitPattern: malloc(size))
+  }
+  ```
+
+  These warnings are in their own diagnostic group (`Unsafe`) and can
+  be suppressed by ackwnowledging the memory-unsafe behavior, for
+  example with an `unsafe` expression:
+
+  ```swift
+  func evilMalloc(size: Int) -> Int {
+    return unsafe Int(bitPattern: malloc(size)) // no warning
+  }
+  ```
+
 ## Swift 6.1
 
 * Previous versions of Swift would incorrectly allow Objective-C `-init...`
@@ -10676,6 +10701,7 @@ using the `.dynamicType` member to retrieve the type of an expression should mig
 [SE-0431]: https://github.com/apple/swift-evolution/blob/main/proposals/0431-isolated-any-functions.md
 [SE-0442]: https://github.com/swiftlang/swift-evolution/blob/main/proposals/0442-allow-taskgroup-childtaskresult-type-to-be-inferred.md
 [SE-0444]: https://github.com/swiftlang/swift-evolution/blob/main/proposals/0444-member-import-visibility.md
+[SE-0458]: https://github.com/swiftlang/swift-evolution/blob/main/proposals/0458-strict-memory-safety.md
 [#64927]: <https://github.com/apple/swift/issues/64927>
 [#42697]: <https://github.com/apple/swift/issues/42697>
 [#42728]: <https://github.com/apple/swift/issues/42728>

userdocs/diagnostic_groups/Unsafe.md

@@ -23,3 +23,14 @@ This diagnostic group includes warnings that identify the use of unsafe language
     return Int(bitPattern: malloc(size))
   }
   ```
+
+These warnings can be suppressed using an `unsafe` expression, which acknowledges the presence of memory-unsafe code. For example:
+
+```swift
+func evilMalloc(size: Int) -> Int {
+  return unsafe Int(bitPattern: malloc(size))
+}
+```
+
+The warnings produced by this diagnostic group can be enabled with the compiler
+flag `-strict-memory-safety`.