(WIP) add test

org.jacoco.core.test/src/org/jacoco/core/internal/instr/SafetySlotTest.java

@@ -0,0 +1,118 @@
+/*******************************************************************************
+ * Copyright (c) 2009, 2023 Mountainminds GmbH & Co. KG and Contributors
+ * This program and the accompanying materials are made available under
+ * the terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *    Evgeny Mandrikov - initial API and implementation
+ *
+ *******************************************************************************/
+package org.jacoco.core.internal.instr;
+
+import org.jacoco.core.instr.Instrumenter;
+import org.jacoco.core.runtime.IRuntime;
+import org.jacoco.core.runtime.RuntimeData;
+import org.jacoco.core.runtime.SystemPropertiesRuntime;
+import org.jacoco.core.test.TargetLoader;
+import org.jacoco.core.test.validation.JavaVersion;
+import org.junit.Test;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+
+public class SafetySlotTest {
+
+	@Test
+	public void original() throws Exception {
+		final byte[] original = createClass();
+
+		new TargetLoader().add("Sample", original).newInstance();
+	}
+
+	@Test
+	public void instrumented() throws Exception {
+		final IRuntime runtime = new SystemPropertiesRuntime();
+		runtime.startup(new RuntimeData());
+
+		final byte[] original = createClass();
+		final byte[] instrumented = new Instrumenter(runtime)
+				.instrument(original, "Sample");
+
+		new TargetLoader().add("Sample", instrumented).newInstance();
+	}
+
+	private static byte[] createClass() throws Exception {
+		final ClassWriter writer = new ClassWriter(0);
+		writer.visit(bytecodeVersion(), Opcodes.ACC_PUBLIC, "Sample", null,
+				"java/lang/Object", new String[0]);
+
+		MethodVisitor mv = writer.visitMethod(Opcodes.ACC_PUBLIC, "<init>",
+				"()V", null, new String[0]);
+		mv.visitCode();
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>",
+				"()V", false);
+
+		// Put a long value (2 slots) on position 0, overwriting 'this'
+		mv.visitLdcInsn(Long.valueOf(42));
+		mv.visitVarInsn(Opcodes.LSTORE, 0);
+
+		mv.visitInsn(Opcodes.ICONST_0);
+		final Label label1 = new Label();
+		mv.visitJumpInsn(Opcodes.IFEQ, label1);
+		mv.visitJumpInsn(Opcodes.GOTO, label1);
+		mv.visitLabel(label1);
+		mv.visitFrame(Opcodes.F_NEW, 1, new Object[] { Opcodes.LONG }, 0,
+				new Object[] {});
+
+		mv.visitLdcInsn(Integer.valueOf(13));
+		mv.visitVarInsn(Opcodes.ISTORE, 2);
+		mv.visitInsn(Opcodes.ICONST_0);
+		final Label label2 = new Label();
+		mv.visitJumpInsn(Opcodes.IFEQ, label2);
+		mv.visitJumpInsn(Opcodes.GOTO, label2);
+		mv.visitLabel(label2);
+		mv.visitFrame(Opcodes.F_NEW, 2,
+				new Object[] { Opcodes.LONG, Opcodes.INTEGER }, 0,
+				new Object[] {});
+
+		mv.visitInsn(Opcodes.RETURN);
+		mv.visitMaxs(2, 3);
+		mv.visitEnd();
+
+		writer.visitEnd();
+
+		return writer.toByteArray();
+	}
+
+	/**
+	 * According to Java Virtual Machine Specification <a href=
+	 * "https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.10.1">
+	 * §4.10.1</a>:
+	 *
+	 * <blockquote>
+	 * <p>
+	 * A class file whose version number is 50.0 or above (§4.1) must be
+	 * verified using the type checking rules given in this section.
+	 * </p>
+	 * <p>
+	 * If, and only if, a class file's version number equals 50.0, then if the
+	 * type checking fails, a Java Virtual Machine implementation may choose to
+	 * attempt to perform verification by type inference (§4.10.2).
+	 * </p>
+	 * </blockquote>
+	 *
+	 * @return {@link Opcodes#V1_7} if supported by current JVM,
+	 *         {@link Opcodes#V1_5} otherwise
+	 */
+	private static int bytecodeVersion() {
+		return JavaVersion.current().isBefore("7") ? Opcodes.V1_5
+				: Opcodes.V1_7;
+	}
+
+}