fix an uninitialized pointer in BridgedSourceLoc

It's so easy to run into undefined behavior in C++

Author: eeckstein

SwiftCompilerSources/Sources/Basic/SourceLoc.swift

@@ -27,11 +27,11 @@ public struct SourceLoc {
     guard bridged.isValid() else {
       return nil
     }
-    self.locationInFile = bridged.opaquePointer!
+    self.locationInFile = bridged.uint8Pointer()!
   }
 
   public var bridged: BridgedSourceLoc {
-    .init(opaquePointer: locationInFile)
+    .init(locationInFile)
   }
 }
 

include/swift/Basic/BasicBridging.h

@@ -88,9 +88,19 @@ class BridgedOwnedString {
   void destroy() const;
 };
 
-struct BridgedSourceLoc {
-  const uint8_t * _Nullable opaquePointer;
+class BridgedSourceLoc {
+  const void * _Nullable opaquePointer;
+public:
+  BridgedSourceLoc() : opaquePointer(nullptr) {}
+  BridgedSourceLoc(const void * _Nullable loc) : opaquePointer(loc) {}
+
   bool isValid() const { return opaquePointer != nullptr; }
+  SWIFT_IMPORT_UNSAFE const uint8_t * _Nullable uint8Pointer() const {
+    return (const uint8_t * _Nullable)opaquePointer;
+  }
+  const char * _Nullable getLoc() const {
+    return (const char * _Nullable)opaquePointer;
+  }
 };
 
 struct BridgedArrayRef {

lib/AST/ASTBridging.cpp

@@ -38,7 +38,7 @@ static_assert(sizeof(BridgedDiagnosticFixIt) >= sizeof(DiagnosticInfo::FixIt),
               "BridgedDiagnosticArgument has wrong size");
 
 static SourceLoc getSourceLoc(BridgedSourceLoc bridgedLoc) {
-  return SourceLoc(llvm::SMLoc::getFromPointer((const char *)bridgedLoc.opaquePointer));
+  return SourceLoc(llvm::SMLoc::getFromPointer(bridgedLoc.getLoc()));
 }
 
 BridgedDiagnosticFixIt::BridgedDiagnosticFixIt(BridgedSourceLoc start, uint32_t length, BridgedStringRef text)
@@ -60,7 +60,7 @@ void DiagnosticEngine_diagnose(
   for (auto arg : getArrayRef<BridgedDiagnosticArgument>(bridgedArguments)) {
     arguments.push_back(arg.get());
   }
-  auto inflight = D->diagnose(SourceLoc(llvm::SMLoc::getFromPointer((const char *)loc.opaquePointer)), diagID, arguments);
+  auto inflight = D->diagnose(SourceLoc(llvm::SMLoc::getFromPointer(loc.getLoc())), diagID, arguments);
 
   // Add highlight.
   if (highlightStart.isValid()) {