avoid adding self-cycle for IntraDirectVFEdge

include/Graphs/VFG.h

@@ -553,8 +553,12 @@ class VFG : public GenericVFGTy
 		PAGNodeToFormalRetMap[uniqueFunRet] = sNode;
 		/// if this uniqueFunRet is a phi node, which means it will receive values from multiple return instructions of fun
 		/// we will set this phi node's def later
-		if (!pag->isPhiNode(uniqueFunRet))
+		/// Ideally, every function uniqueFunRet should be a PhiNode (PAGBuilder.cpp), unless it does not have ret instruction
+		if (!pag->isPhiNode(uniqueFunRet)){
+			std::string warn = fun->getName();
+			SVFUtil::writeWrnMsg(warn + " does not have any ret instruction!");
 			setDef(uniqueFunRet, sNode);
+		}
     }
     /// Add a callsite Receive VFG node
     inline void addActualRetVFGNode(const PAGNode* ret,const CallBlockNode* cs)

include/SVF-FE/LLVMUtil.h

@@ -59,6 +59,7 @@ inline const Function* getLLVMFunction(const Value* val)
 
 
 /// Return true if the call is an external call (external library in function summary table)
+/// If the libary function is redefined in the application code (e.g., memcpy), it will return false and will not be treated as an external call.
 //@{
 inline bool isExtCall(const SVFFunction* fun)
 {

lib/Graphs/VFG.cpp

@@ -529,8 +529,12 @@ VFGEdge* VFG::addIntraDirectVFEdge(NodeID srcId, NodeID dstId)
     }
     else
     {
-        IntraDirSVFGEdge* directEdge = new IntraDirSVFGEdge(srcNode,dstNode);
-        return (addVFGEdge(directEdge) ? directEdge : nullptr);
+    	if(srcNode!=dstNode){
+    		IntraDirSVFGEdge* directEdge = new IntraDirSVFGEdge(srcNode,dstNode);
+    		return (addVFGEdge(directEdge) ? directEdge : nullptr);
+    	}
+    	else
+    		return nullptr;
     }
 }