commit 4e49952712ff9b1b1696cb07580b2b24a3ca99e1
author Matthew Curtis <mcurtis@codeaurora.org> Thu Oct 03 12:14:24 2013 +0000
committer Matthew Curtis <mcurtis@codeaurora.org> Thu Oct 03 12:14:24 2013 +0000
tree 1fe3fd445e8be93463a398860c55165293c3fa28
parent 618c28547a7f7cc785a6c6301f79febf5a584f9e

Gracefully (and correctly) handle init of multiple union members

We now emit warnings when doing so and code generation is consistent
with GCC. Note that the C99 spec is unclear as to the precise
behavior.

See also ...
Bug:
  http://llvm.org/bugs/show_bug.cgi?id=16644 and

cfe-dev discussion:
  http://lists.cs.uiuc.edu/pipermail/cfe-dev/2013-September/031918.html



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191890 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaInit.cpp

diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index afd9393..e407253 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -1868,8 +1868,29 @@
     // the initializer list.
     if (RT->getDecl()->isUnion()) {
       FieldIndex = 0;
-      if (!VerifyOnly)
+      if (!VerifyOnly) {
+        FieldDecl *CurrentField = StructuredList->getInitializedFieldInUnion();
+        if (CurrentField && CurrentField != *Field) {
+          assert(StructuredList->getNumInits() == 1
+                 && "A union should never have more than one initializer!");
+
+          // we're about to throw away an initializer, emit warning
+          SemaRef.Diag(D->getFieldLoc(),
+                       diag::warn_initializer_overrides)
+            << D->getSourceRange();
+          Expr *ExistingInit = StructuredList->getInit(0);
+          SemaRef.Diag(ExistingInit->getLocStart(),
+                       diag::note_previous_initializer)
+            << /*FIXME:has side effects=*/0
+            << ExistingInit->getSourceRange();
+
+          // remove existing initializer
+          StructuredList->resizeInits(SemaRef.Context, 0);
+          StructuredList->setInitializedFieldInUnion(0);
+        }
+
         StructuredList->setInitializedFieldInUnion(*Field);
+      }
     }
 
     // Make sure we can use this declaration.