Fix constexpr execution of if statement with static_assert declaration substatement

Stop null dereference in ExecIf when thenClauseExec is null. This happens with
throw declaration in thenClause, and ExecIf already allows for null in elseClauseExec
so this is a bit more consistent.

Null thenClauseExec can be from encountered valid static_assert declaration,
handle it during constexpr execution as new special problem type STATIC_ASSERT_FAILED.

Author: i-garrison

core/org.eclipse.cdt.core/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.cdt.core; singleton:=true
-Bundle-Version: 9.2.100.qualifier
+Bundle-Version: 9.3.0.qualifier
 Bundle-Activator: org.eclipse.cdt.core.CCorePlugin
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTDeclarationStatement.java

@@ -24,6 +24,7 @@
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.IASTAmbiguityParent;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.ExecDeclarationStatement;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.ExecReturn;
 
 /**
  * @author jcamelon
@@ -130,9 +131,15 @@ public void addAttributeSpecifier(IASTAttributeSpecifier attributeSpecifier) {
 
 	@Override
 	public ICPPExecution getExecution() {
-		if (declaration instanceof ICPPExecutionOwner) {
-			ICPPExecutionOwner execOwner = (ICPPExecutionOwner) declaration;
-			return new ExecDeclarationStatement(execOwner.getExecution());
+		if (declaration instanceof ICPPExecutionOwner execOwner) {
+			ICPPExecution execution = execOwner.getExecution();
+			if (execution instanceof ExecReturn) {
+				// CPPASTStaticAssertionDeclaration simulates error handling via ExecReturn
+				// with conditional expression which must be executed as is to return problem value
+				return execution;
+			} else {
+				return new ExecDeclarationStatement(execution);
+			}
 		}
 		return null;
 	}

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTStaticAssertionDeclaration.java

@@ -13,20 +13,32 @@
  *******************************************************************************/
 package org.eclipse.cdt.internal.core.dom.parser.cpp;
 
+import static org.eclipse.cdt.core.dom.ast.IASTExpression.ValueCategory.PRVALUE;
+
 import org.eclipse.cdt.core.dom.ast.ASTVisitor;
 import org.eclipse.cdt.core.dom.ast.IASTExpression;
 import org.eclipse.cdt.core.dom.ast.IASTNode;
+import org.eclipse.cdt.core.dom.ast.IBinding;
+import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTExpression;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTLiteralExpression;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTStaticAssertDeclaration;
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.IASTAmbiguityParent;
+import org.eclipse.cdt.internal.core.dom.parser.IntegralValue;
+import org.eclipse.cdt.internal.core.dom.parser.ProblemType;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.EvalConditional;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.EvalFixed;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.ExecReturn;
 
 public class CPPASTStaticAssertionDeclaration extends ASTNode
-		implements ICPPASTStaticAssertDeclaration, IASTAmbiguityParent {
+		implements ICPPASTStaticAssertDeclaration, IASTAmbiguityParent, ICPPExecutionOwner {
 
 	private IASTExpression fCondition;
 	private final ICPPASTLiteralExpression fMessage;
 
+	public static final ICPPEvaluation STATIC_ASSERT_FAILED = new EvalFixed(ProblemType.STATIC_ASSERT_FAILED, PRVALUE,
+			IntegralValue.STATIC_ASSERT_FAILED_ERROR);
+
 	/**
 	 * Constructor for C++17 static_assert with only a condition.
 	 *
@@ -101,4 +113,21 @@ public void replace(IASTNode child, IASTNode other) {
 			other.setPropertyInParent(child.getPropertyInParent());
 		}
 	}
+
+	@Override
+	public ICPPExecution getExecution() {
+		// Naturally this would be compilation error; simulate executing this statement via return with evaluation problem.
+		// If no evaluation of condition is available, treat it as unsatisfied condition too.
+		final ICPPEvaluation conditionExprEval = getCondition() instanceof ICPPASTExpression conditionExpr
+				? conditionExpr.getEvaluation()
+				: CPPASTLiteralExpression.INT_ZERO.getEvaluation();
+
+		ICPPEvaluation conditionalEval = new EvalConditional(conditionExprEval, null, STATIC_ASSERT_FAILED, false,
+				false, (IBinding) null);
+
+		//		ICPPExecution constexprIfExecution = new ExecIf(true, null, conditionExprEval, null, null,
+		//				new ExecReturn(STATIC_ASSERT_FAILED));
+
+		return new ExecReturn(conditionalEval);
+	}
 }

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/ExecIf.java

@@ -49,11 +49,10 @@ private boolean conditionSatisfied(ActivationRecord record, ConstexprEvaluationC
 	public ICPPExecution executeForFunctionCall(ActivationRecord record, ConstexprEvaluationContext context) {
 		EvalUtil.executeStatement(initStmtExec, record, context);
 		if (conditionSatisfied(record, context)) {
-			return EvalUtil.executeStatement(thenClauseExec, record, context);
-		} else if (elseClauseExec != null) {
-			return EvalUtil.executeStatement(elseClauseExec, record, context);
+			return thenClauseExec != null ? EvalUtil.executeStatement(thenClauseExec, record, context) : null;
+		} else {
+			return elseClauseExec != null ? EvalUtil.executeStatement(elseClauseExec, record, context) : null;
 		}
-		return null;
 	}
 
 	@Override
@@ -76,12 +75,12 @@ public ICPPExecution instantiate(InstantiationContext context, int maxDepth) {
 				 * might have side effects so it needs to be preserved in the instantiated
 				 * execution even if one of its branch has become null
 				 */
-				newThenClauseExec = thenClauseExec.instantiate(context, maxDepth);
+				newThenClauseExec = thenClauseExec != null ? thenClauseExec.instantiate(context, maxDepth) : null;
 			} else {
 				newElseClauseExec = elseClauseExec != null ? elseClauseExec.instantiate(context, maxDepth) : null;
 			}
 		} else {
-			newThenClauseExec = thenClauseExec.instantiate(context, maxDepth);
+			newThenClauseExec = thenClauseExec != null ? thenClauseExec.instantiate(context, maxDepth) : null;
 			newElseClauseExec = elseClauseExec != null ? elseClauseExec.instantiate(context, maxDepth) : null;
 		}