Ensure that the most recent declaration of a tentative definition wins

when generating a common definition.

llvm-svn: 69287

2 files changed, 10 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 81bff667fb9..d1d67a11b8a 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -424,9 +424,11 @@ void CodeGenModule::EmitDeferred() {
     EmitGlobalDefinition(D);
   }
 
-  // Emit any tentative definitions.
-  for (std::vector<const VarDecl*>::iterator it = TentativeDefinitions.begin(),
-         ie = TentativeDefinitions.end(); it != ie; ++it)
+  // Emit any tentative definitions, in reverse order so the most
+  // important (merged) decl will be seen and emitted first.
+  for (std::vector<const VarDecl*>::reverse_iterator 
+         it = TentativeDefinitions.rbegin(), ie = TentativeDefinitions.rend(); 
+       it != ie; ++it)
     EmitTentativeDefinition(*it);
 }
 
diff --git a/clang/test/CodeGen/tentative-decls.c b/clang/test/CodeGen/tentative-decls.c
index 4604f2f4297..7fb396a5078 100644
--- a/clang/test/CodeGen/tentative-decls.c
+++ b/clang/test/CodeGen/tentative-decls.c
@@ -25,4 +25,9 @@ int *f1() {
   return b;
 }
 
+// Check that the most recent tentative definition wins.
+// RUN: grep '@c = common global \[4 x .*\] zeroinitializer' %t &&
+int c[];
+int c[4];
+
 // RUN: true