[analyzer] Do not duplicate call graph nodes for function that has definition and forward declaration.

[IvanSidorenko]

Summary

Fix in call graph construction: don't build call graph node for callee function twice for functions with forward declarations.

Maybe the same fix should be done and for VisitObjCMethodDecl. Unfortunately, I have not enough expertise in ObjC, so I did not touch this code.

Test case:
void do_nothing() {}
void test_single_call();
void test_single_call() {

do_nothing();

}

Output for the test case WITHOUT patch:
Function: test_single_call calls: do_nothing do_nothing
Function: do_nothing calls:

Output for the test case WITH patch:
Function: test_single_call calls: do_nothing
Function: do_nothing calls:

[zaks.anna]

Looks good. Thank you for catching this!

Do you have commit access or should I commit on your behalf?

[a.sidorin]

Anna, I will commit. Thank you!

cfe/trunk/include/clang/Analysis/CallGraph.h

public:
 
   void addNodesForBlocks(DeclContext *D);
 
   /// Part of recursive declaration visitation. We recursively visit all the
   /// declarations to collect the root functions.
   bool VisitFunctionDecl(FunctionDecl *FD) {
     // We skip function template definitions, as their semantics is
     // only determined when they are instantiated.
-    if (includeInGraph(FD)) {
+    if (includeInGraph(FD) && FD->isThisDeclarationADefinition()) {
       // Add all blocks declared inside this function to the graph.
       addNodesForBlocks(FD);
       // If this function has external linkage, anything could call it.
       // Note, we are not precise here. For example, the function could have
       // its address taken.
       addNodeForDecl(FD, FD->isGlobal());
     }
     return true;

cfe/trunk/test/Analysis/debug-CallGraph.c

 void ccc();
 void ddd() { ccc(); }
 void ccc() {}
 
 void eee();
 void eee() {}
 void fff() { eee(); }
 
+// This test case tests that forward declaration for the top-level function
+// does not affect call graph construction.
+void do_nothing() {}
+void test_single_call();
+void test_single_call() {
+  do_nothing();
+}
+
 // CHECK:--- Call graph Dump ---
-// CHECK-NEXT: {{Function: < root > calls: get5 add test_add mmm foo aaa < > bbb ccc ddd eee fff $}}
+// CHECK-NEXT: {{Function: < root > calls: get5 add test_add mmm foo aaa < > bbb ddd ccc eee fff do_nothing test_single_call $}}
+// CHECK-NEXT: {{Function: test_single_call calls: do_nothing $}}
+// CHECK-NEXT: {{Function: do_nothing calls: $}}
 // CHECK-NEXT: {{Function: fff calls: eee $}}
 // CHECK-NEXT: {{Function: eee calls: $}}
 // CHECK-NEXT: {{Function: ddd calls: ccc $}}
 // CHECK-NEXT: {{Function: ccc calls: $}}
 // CHECK-NEXT: {{Function: bbb calls: < > $}}
 // CHECK-NEXT: {{Function: < > calls: foo $}}
 // CHECK-NEXT: {{Function: aaa calls: foo $}}
 // CHECK-NEXT: {{Function: foo calls: mmm $}}
 // CHECK-NEXT: {{Function: mmm calls: $}}
 // CHECK-NEXT: {{Function: test_add calls: add get5 $}}
 // CHECK-NEXT: {{Function: add calls: $}}
 // CHECK-NEXT: {{Function: get5 calls: $}}