[SemaObjC] Fix a -Wbridge-cast false-positive

Clang used to emit a bad -Wbridge-cast diagnostic on the cast in the attached
test. This was because, after 09abecef7, struct __CFString was not added to
lookup, so the objc_bridge attribute wasn't getting duplicated onto the most
recent declaration, causing us to fail to find it in getObjCBridgeAttr. This
patch fixes this by instead walking through the redeclarations to find an
appropriate bridge attribute. rdar://72823399

Differential revision: https://reviews.llvm.org/D99661

diff --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index f5456ee..71c1500 100644 (file)
--- a/clang/lib/Sema/SemaExprObjC.cpp
+++ b/clang/lib/Sema/SemaExprObjC.cpp
@@ -3847,9 +3847,12 @@ static inline T *getObjCBridgeAttr(const TypedefType *TD) {
   QualType QT = TDNDecl->getUnderlyingType();
   if (QT->isPointerType()) {
     QT = QT->getPointeeType();
-    if (const RecordType *RT = QT->getAs<RecordType>())
-      if (RecordDecl *RD = RT->getDecl()->getMostRecentDecl())
-        return RD->getAttr<T>();
+    if (const RecordType *RT = QT->getAs<RecordType>()) {
+      for (auto *Redecl : RT->getDecl()->getMostRecentDecl()->redecls()) {
+        if (auto *attr = Redecl->getAttr<T>())
+          return attr;
+      }
+    }
   }
   return nullptr;
 }

diff --git a/clang/test/SemaObjCXX/bridge-cast-redecl.mm b/clang/test/SemaObjCXX/bridge-cast-redecl.mm
new file mode 100644 (file)
index 0000000..c640e52
--- /dev/null
+++ b/clang/test/SemaObjCXX/bridge-cast-redecl.mm
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -std=gnu++17 -verify %s
+
+// expected-no-diagnostics
+
+typedef const struct __CFString * CFStringRef;
+
+extern "C" {
+  typedef const struct __attribute__((objc_bridge(NSString))) __CFString * CFStringRef;
+  typedef struct __attribute__((objc_bridge_mutable(NSMutableString))) __CFString * CFMutableStringRef;
+}
+
+@interface NSString @end
+@interface NSMutableString : NSString @end
+
+void CFStringGetLength(CFStringRef theString);
+
+int main() {
+  CFStringGetLength((__bridge CFStringRef)(NSString *)0);
+}