[clang] 803b792 - [SemaObjC] Fix a -Wbridge-cast false-positive

[Erik Pilkington via cfe-commits]

Author: Erik Pilkington
Date: 2021-04-05T11:41:40-04:00
New Revision: 803b79221edfc2517e6bfc373e5f55609565b0e4

URL: https://github.com/llvm/llvm-project/commit/803b79221edfc2517e6bfc373e5f55609565b0e4
DIFF: https://github.com/llvm/llvm-project/commit/803b79221edfc2517e6bfc373e5f55609565b0e4.diff

LOG: [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

Added: 
    clang/test/SemaObjCXX/bridge-cast-redecl.mm

Modified: 
    clang/lib/Sema/SemaExprObjC.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index f5456ee0711e5..71c150027cdd6 100644
--- 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
index 0000000000000..c640e52922938
--- /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;
+}
+
+ at interface NSString @end
+ at interface NSMutableString : NSString @end
+
+void CFStringGetLength(CFStringRef theString);
+
+int main() {
+  CFStringGetLength((__bridge CFStringRef)(NSString *)0);
+}