improve decl merging logic to be more correct with

functions.  Patch contributed by Nuno Lopes, thanks!

llvm-svn: 43757

clang/Sema/SemaDecl.cpp

@@ -246,6 +246,11 @@ FunctionDecl *Sema::MergeFunctionDecl(FunctionDecl *New, ScopedDecl *OldD) {
     return New;
   }
 
+  if (New->getBody() == 0 && 
+      Old->getCanonicalType() == New->getCanonicalType()) {
+    return 0;
+  }
+  
   // TODO: CHECK FOR CONFLICTS, multiple decls with same name in one scope.
   // TODO: This is totally simplistic.  It should handle merging functions
   // together etc, merging extern int X; int X; ...

clang/test/Sema/merge-decls.c

@@ -0,0 +1,8 @@
+// RUN: clang %s -verify -fsyntax-only
+
+void foo(void);
+void foo(void) {} // expected-error{{previous definition is here}}
+void foo(void);
+void foo(void);
+
+void foo(int); // expected-error {{redefinition of 'foo'}}