Bug 327375 control flow graph regression - dead connector nodes

basically for the code like
if (a) return 1; else return 2;
a++; // this should be a dead code node

but we don't check connector node of "if" and don't add
it to dead nodes graph resulting it this code not being marked as dead,
which can lead to false positives or false negatives for checkers that
use that. Same apply for other control statements...

Change-Id: Iafb4b48ca960f0ffab2c0265285a31cb08eb0d11

1 files changed, 30 insertions, 11 deletions

diff --git a/codan/org.eclipse.cdt.codan.core.cxx/src/org/eclipse/cdt/codan/core/cxx/internal/model/cfg/ControlFlowGraphBuilder.java b/codan/org.eclipse.cdt.codan.core.cxx/src/org/eclipse/cdt/codan/core/cxx/internal/model/cfg/ControlFlowGraphBuilder.java
index 07aea511da1..8e3094593a7 100644
--- a/codan/org.eclipse.cdt.codan.core.cxx/src/org/eclipse/cdt/codan/core/cxx/internal/model/cfg/ControlFlowGraphBuilder.java
+++ b/codan/org.eclipse.cdt.codan.core.cxx/src/org/eclipse/cdt/codan/core/cxx/internal/model/cfg/ControlFlowGraphBuilder.java
@@ -312,16 +312,23 @@ public class ControlFlowGraphBuilder {
 		addOutgoing(ifNode, elseNode);
 		IBasicBlock els = createSubGraph(elseNode, body.getElseClause());
 		addJump(els, mergeNode);
+		fixConnector(mergeNode);
 		return mergeNode;
 	}
 
+	protected void fixConnector(IConnectorNode mergeNode) {
+		if (mergeNode.getIncomingSize()==0)
+			dead.add(mergeNode); // dead connector node
+	}
+
 	private IBasicBlock createSwitch(IBasicBlock prev, IASTSwitchStatement body) {
 		DecisionNode node = factory.createDecisionNode(body.getControllerExpression());
 		addOutgoing(prev, node);
-		IConnectorNode conn = factory.createConnectorNode();
-		node.setMergeNode(conn);
-		createSwitchBody(node, conn, body.getBody());
-		return conn;
+		IConnectorNode mergeNode = factory.createConnectorNode();
+		node.setMergeNode(mergeNode);
+		createSwitchBody(node, mergeNode, body.getBody());
+		fixConnector(mergeNode);
+		return mergeNode;
 	}
 
 	private void createSwitchBody(IDecisionNode switchNode, IConnectorNode mergeNode, IASTStatement body) {
@@ -380,9 +387,13 @@ public class ControlFlowGraphBuilder {
 		IConnectorNode savedBreak = outerBreak;
 		outerContinue = nContinue;
 		outerBreak = nBreak;
-		IBasicBlock endBody = createSubGraph(loopStart, forNode.getBody());
-		outerContinue = savedContinue;
-		outerBreak = savedBreak;
+		IBasicBlock endBody = decision;
+		try {
+			endBody = createSubGraph(loopStart, forNode.getBody());
+		} finally {
+			outerContinue = savedContinue;
+			outerBreak = savedBreak;
+		}
 		// inc
 		IPlainNode inc = factory.createPlainNode(forNode.getIterationExpression());
 		addOutgoing(endBody, nContinue);
@@ -393,6 +404,7 @@ public class ControlFlowGraphBuilder {
 		IBranchNode loopEnd = factory.createBranchNode(IBranchNode.ELSE);
 		addOutgoing(decision, loopEnd);
 		addJump(loopEnd, nBreak);
+		fixConnector(nBreak);
 		return nBreak;
 	}
 
@@ -432,6 +444,7 @@ public class ControlFlowGraphBuilder {
 		IBranchNode loopEnd = factory.createBranchNode(IBranchNode.ELSE);
 		addOutgoing(decision, loopEnd);
 		addJump(loopEnd, nBreak);
+		fixConnector(nBreak);
 		return nBreak;
 	}
 
@@ -453,16 +466,21 @@ public class ControlFlowGraphBuilder {
 		IConnectorNode savedBreak = outerBreak;
 		outerContinue = nContinue;
 		outerBreak = nBreak;
-		IBasicBlock endBody = createSubGraph(loopStart, body.getBody());
-		// Restore
-		outerContinue = savedContinue;
-		outerBreak = savedBreak;
+		IBasicBlock endBody = decision;
+		try {
+			endBody = createSubGraph(loopStart, body.getBody());
+		} finally {
+			// Restore
+			outerContinue = savedContinue;
+			outerBreak = savedBreak;
+		}
 		// Backward jump
 		addJump(endBody, nContinue, true);
 		// Connect with else branch
 		IBranchNode loopEnd = factory.createBranchNode(IBranchNode.ELSE);
 		addOutgoing(decision, loopEnd);
 		addJump(loopEnd, nBreak);
+		fixConnector(nBreak);
 		return nBreak;
 	}
 
@@ -500,6 +518,7 @@ public class ControlFlowGraphBuilder {
 		// Add break connector
 		decision.setMergeNode(nBreak);
 		addJump(loopEnd, nBreak);
+		fixConnector(nBreak);
 		return nBreak;
 	}