我在做什么
我正在使用 ASM 和 javaagent 来检测类以报告它们的覆盖率(为什么我不使用 jacoco？嗯，这与这个问题无关)，基本逻辑是，每次 visitLineNumber 被调用时，我检测了一些方法调用(就在访问下一条指令之前)以记录命中行号。
问题描述
这么简单的逻辑，一个类得到了ClassFormatError:
java.lang.ClassFormatError: StackMapTable format error: bad offset for Uninitialized in method org.apache.commons.math.ode.ContinuousOutputModelTest.buildInterpolator(D[DD)Lorg/apache/commons/math/ode/sampling/StepInterpolator;
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
...
检测前的字节码如下所示。堆栈映射帧所在的指令是@16(offset_delta = 16)和@17(offset_delta = 0)。
private org.apache.commons.math.ode.sampling.StepInterpolator buildInterpolator(double, double[], double);
descriptor: (D[DD)Lorg/apache/commons/math/ode/sampling/StepInterpolator;
flags: ACC_PRIVATE
Code:
stack=7, locals=7, args_size=4
0: new #66 // class org/apache/commons/math/ode/sampling/DummyStepInterpolator
3: dup
4: aload_3
5: dload 4
7: dload_1
8: dcmpl
9: iflt 16
12: iconst_1
13: goto 17
16: iconst_0
17: invokespecial #67 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator."<init>":([DZ)V
20: astore 6
22: aload 6
24: dload_1
25: invokevirtual #68 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.storeTime:(D)V
28: aload 6
30: invokevirtual #69 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.shift:()V
33: aload 6
35: dload 4
37: invokevirtual #68 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.storeTime:(D)V
40: aload 6
42: areturn
...
StackMapTable: number_of_entries = 2
frame_type = 255 /* full_frame */
offset_delta = 16
locals = [ class org/apache/commons/math/ode/ContinuousOutputModelTest, double, class "[D", double ]
stack = [ uninitialized 0, uninitialized 0, class "[D" ]
frame_type = 255 /* full_frame */
offset_delta = 0
locals = [ class org/apache/commons/math/ode/ContinuousOutputModelTest, double, class "[D", double ]
stack = [ uninitialized 0, uninitialized 0, class "[D", int ]
检测后，字节码变为:
private org.apache.commons.math.ode.sampling.StepInterpolator buildInterpolator(double, double[], double);
descriptor: (D[DD)Lorg/apache/commons/math/ode/sampling/StepInterpolator;
flags: ACC_PRIVATE
Code:
stack=10, locals=7, args_size=4
0: ldc_w #264 // String org/apache/commons/math/ode/ContinuousOutputModelTest
3: ldc_w #344 // String buildInterpolator
6: ldc_w #345 // int 169
9: invokestatic #272 // Method org/test/cov/CoverageCollector.reportCoverage:(Ljava/lang/String;Ljava/lang/String;I)V
12: new #66 // class org/apache/commons/math/ode/sampling/DummyStepInterpolator
15: dup
16: aload_3
17: dload 4
19: dload_1
20: dcmpl
21: iflt 28
24: iconst_1
25: goto 29
28: iconst_0
29: invokespecial #67 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator."<init>":([DZ)V
32: astore 6
34: ldc_w #264 // String org/apache/commons/math/ode/ContinuousOutputModelTest
37: ldc_w #344 // String buildInterpolator
40: ldc_w #346 // int 170
43: invokestatic #272 // Method org/test/cov/CoverageCollector.reportCoverage:(Ljava/lang/String;Ljava/lang/String;I)V
46: aload 6
48: dload_1
49: invokevirtual #68 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.storeTime:(D)V
52: ldc_w #264 // String org/apache/commons/math/ode/ContinuousOutputModelTest
55: ldc_w #344 // String buildInterpolator
58: ldc_w #347 // int 171
61: invokestatic #272 // Method org/test/cov/CoverageCollector.reportCoverage:(Ljava/lang/String;Ljava/lang/String;I)V
64: aload 6
66: invokevirtual #69 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.shift:()V
69: ldc_w #264 // String org/apache/commons/math/ode/ContinuousOutputModelTest
72: ldc_w #344 // String buildInterpolator
75: ldc_w #348 // int 172
78: invokestatic #272 // Method org/test/cov/CoverageCollector.reportCoverage:(Ljava/lang/String;Ljava/lang/String;I)V
81: aload 6
83: dload 4
85: invokevirtual #68 // Method org/apache/commons/math/ode/sampling/DummyStepInterpolator.storeTime:(D)V
88: ldc_w #264 // String org/apache/commons/math/ode/ContinuousOutputModelTest
91: ldc_w #344 // String buildInterpolator
94: ldc_w #349 // int 173
97: invokestatic #272 // Method org/test/cov/CoverageCollector.reportCoverage:(Ljava/lang/String;Ljava/lang/String;I)V
100: aload 6
102: areturn
...
StackMapTable: number_of_entries = 2
frame_type = 255 /* full_frame */
offset_delta = 28
locals = [ class org/apache/commons/math/ode/ContinuousOutputModelTest, double, class "[D", double ]
stack = [ uninitialized 0, uninitialized 0, class "[D" ]
frame_type = 255 /* full_frame */
offset_delta = 0
locals = [ class org/apache/commons/math/ode/ContinuousOutputModelTest, double, class "[D", double ]
stack = [ uninitialized 0, uninitialized 0, class "[D", int ]
我没有发现 StackMapTable 有任何问题。关于此 StackMapTable 格式为何无效的任何想法？
以下是我的检测代码:
class CoverageMethodVisitor extends MethodVisitor {
private String slashClassName;
private String methodName;
private int currentLine;
private boolean isJUnit3TestClass;
private boolean hasTestAnnotation;
private boolean isTestMethod;
private int classVersion;
private boolean isRightAfterLabel;
protected CoverageMethodVisitor(MethodVisitor methodVisitor, String className, String methodName, boolean isJUnit3TestClass, int classVersion) {
super(ASM_VERSION, methodVisitor);
this.slashClassName = className;
this.methodName = methodName;
this.isJUnit3TestClass = isJUnit3TestClass;
this.classVersion = classVersion;
}
private void instrumentReportCoverageInvocation() {
super.visitLdcInsn(slashClassName);
super.visitLdcInsn(methodName);
super.visitLdcInsn(currentLine);
super.visitMethodInsn(INVOKESTATIC, "org/test/cov/CoverageCollector",
"reportCoverage", "(Ljava/lang/String;Ljava/lang/String;I)V", false);
}
@Override
public void visitInsn(int opcode) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitInsn(opcode);
}
@Override
public void visitIntInsn(int opcode, int operand) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitIntInsn(opcode, operand);
}
@Override
public void visitVarInsn(int opcode, int varIndex) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitVarInsn(opcode, varIndex);
}
@Override
public void visitTypeInsn(int opcode, String type) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitTypeInsn(opcode, type);
}
@Override
public void visitFieldInsn(int opcode, String owner, String name, String descriptor) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitFieldInsn(opcode, owner, name, descriptor);
}
@Override
public void visitMethodInsn(int opcode, String owner, String name, String descriptor, boolean isInterface) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitMethodInsn(opcode, owner, name, descriptor, isInterface);
}
@Override
public void visitInvokeDynamicInsn(String name, String descriptor, Handle bootstrapMethodHandle, Object... bootstrapMethodArguments) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitInvokeDynamicInsn(name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
}
@Override
public void visitJumpInsn(int opcode, Label label) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitJumpInsn(opcode, label);
}
@Override
public void visitLdcInsn(Object value) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitLdcInsn(value);
}
@Override
public void visitIincInsn(int varIndex, int increment) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitIincInsn(varIndex, increment);
}
@Override
public void visitTableSwitchInsn(int min, int max, Label dflt, Label... labels) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitTableSwitchInsn(min, max, dflt, labels);
}
@Override
public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitLookupSwitchInsn(dflt, keys, labels);
}
@Override
public void visitMultiANewArrayInsn(String descriptor, int numDimensions) {
if (isRightAfterLabel) instrumentReportCoverageInvocation(); isRightAfterLabel = false;
super.visitMultiANewArrayInsn(descriptor, numDimensions);
}
@Override
public void visitMaxs(int maxStack, int maxLocals) {
super.visitMaxs(maxStack+3, maxLocals);
}
/**
* Should not report line coverage immediately after the visitLineNumber. visitLineNumber is called right after
* visitLabel, but it is very possible that a stack map frame is after the label, if insert instructions right
* after the label, the original stack map frame will be messed up. So instead, insert instructions before the
* first instruction after the label. */
@Override
public void visitLineNumber(int line, Label start) {
super.visitLineNumber(line, start);
currentLine = line;
isRightAfterLabel = true;
}
}
/** */中的注释其实是我的猜测，不确定是否正确。
编辑:
很抱歉，我误解了 offset_delta = 0 的含义，因为 java spec提及:
The bytecode offset at which a frame applies is calculated by adding offset_delta + 1 to the bytecode offset of the previous frame, unless the previous frame is the initial frame of the method, ...
总结
错误原因
bad offset for Uninitialized中的Uninitialized指的是由NEW指令(原始字节码中的第一条指令)产生的未初始化对象).由于原始堆栈映射框架需要在 NEW 指令之前使用标签(比如 L0)来表示其 locals 中的未初始化对象，并且stack，检测代码中的L0不再代表NEW指令，抛出此类错误。
解决方案
由于检测代码中的 L0 不再代表 NEW 指令，我们需要为该 NEW 指令创建一个新标签，并在两个堆栈映射框架中用新标签替换旧标签 L0。如果指定了COMPUTE_FRAME，这样的堆栈映射帧(重新)计算将自动完成，但这里我们需要手动完成，因为COMPUTE_FRAME 没有被使用以避免其他潜在问题.
最佳答案
作为Rafael Winterhalter said ，标签用于引用 NEW 指令，因此将指令放在标签位置和指令之间会破坏此引用。当指令创建的未初始化实例位于堆栈或局部变量中时，堆栈映射框架需要此类引用。
由于在 NEW 指令之前插入代码时要保留原始位置作为分支目标或行号开始，因此必须为注入(inject)代码和插入代码之间的代码位置创建一个新标签old NEW 指令，然后替换堆栈映射框架使用的标签(并且仅替换堆栈映射框架使用的标签)。
请注意，当使用 COMPUTE_FRAMES 选项时，这不是必需的，该选项将从头开始重新计算帧并且不使用旧标签，但是，不使用此选项实际上是一个合理的策略，因为它很昂贵且容易出错。为了注入(inject)没有分支的简单日志记录语句，我们可以保留原始帧，即使检查 NEW 指令的特殊情况会使它稍微困难一些。
以下方法访问者实现上述策略。对于我的测试，我只是注入(inject)了一个普通的 System.out.println(...); 语句。
class CoverageMethodVisitor extends MethodVisitor {
private final String slashClassName;
private final String methodName;
private final Map<Label,Label> translateForUninitialized = new HashMap<>();
private Label lastLabel;
private int newLineNumber = -1;
protected CoverageMethodVisitor(MethodVisitor mv,String clName,String methodName){
super(Opcodes.ASM9, mv);
this.slashClassName = clName;
this.methodName = methodName;
}
@Override
public void visitLineNumber(int line, Label start) {
newLineNumber = line;
super.visitLineNumber(line, start);
}
@Override
public void visitLabel(Label label) {
lastLabel = label;
super.visitLabel(label);
}
@Override
public void visitTypeInsn(int opcode, String type) {
if(instrumentReportCoverageInvocation() && opcode == Opcodes.NEW) {
if(lastLabel != null) {
Label newLabel = new Label();
super.visitLabel(newLabel);
translateForUninitialized.put(lastLabel, newLabel);
}
}
super.visitTypeInsn(opcode, type);
}
@Override
public void visitFrame(int type,
int numLocal, Object[] local, int numStack, Object[] stack) {
switch(type) {
case Opcodes.F_NEW, Opcodes.F_FULL -> {
local = replaceLabels(numLocal, local);
stack = replaceLabels(numStack, stack);
}
case Opcodes.F_APPEND -> local = replaceLabels(numLocal, local);
case Opcodes.F_CHOP, Opcodes.F_SAME -> {}
case Opcodes.F_SAME1 -> stack = replaceLabels(1, stack);
default -> throw new AssertionError();
}
super.visitFrame(type, numLocal, local, numStack, stack);
}
private Object[] replaceLabels(int num, Object[] array) {
Object[] result = array;
for(int ix = 0; ix < num; ix++) {
Label repl = translateForUninitialized.get(result[ix]);
if(repl == null) continue;
if(result == array) result = array.clone();
result[ix] = repl;
}
return result;
}
private boolean instrumentReportCoverageInvocation() {
int lineNumber = newLineNumber;
if(lineNumber < 0) return false;
newLineNumber = -1;
super.visitFieldInsn(Opcodes.GETSTATIC,
"java/lang/System", "out", "Ljava/io/PrintStream;");
super.visitLdcInsn(slashClassName + "." + methodName + " line " + lineNumber);
super.visitMethodInsn(Opcodes.INVOKEVIRTUAL,
"java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
return true;
}
@Override
public void visitLdcInsn(Object value) {
instrumentReportCoverageInvocation();
super.visitLdcInsn(value);
}
@Override
public void visitInsn(int opcode) {
instrumentReportCoverageInvocation();
super.visitInsn(opcode);
}
@Override
public void visitIntInsn(int opcode, int operand) {
instrumentReportCoverageInvocation();
super.visitIntInsn(opcode, operand);
}
@Override
public void visitVarInsn(int opcode, int varIndex) {
instrumentReportCoverageInvocation();
super.visitVarInsn(opcode, varIndex);
}
@Override
public void visitFieldInsn(int opcode,
String owner, String name, String descriptor) {
instrumentReportCoverageInvocation();
super.visitFieldInsn(opcode, owner, name, descriptor);
}
@Override
public void visitMethodInsn(int opcode,
String owner, String name, String descriptor, boolean isInterface) {
instrumentReportCoverageInvocation();
super.visitMethodInsn(opcode, owner, name, descriptor, isInterface);
}
@Override
public void visitInvokeDynamicInsn(
String name, String descriptor, Handle bootstrapMethodHandle,
Object... bootstrapMethodArguments) {
instrumentReportCoverageInvocation();
super.visitInvokeDynamicInsn(
name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
}
@Override
public void visitJumpInsn(int opcode, Label label) {
instrumentReportCoverageInvocation();
super.visitJumpInsn(opcode, label);
}
@Override
public void visitIincInsn(int varIndex, int increment) {
instrumentReportCoverageInvocation();
super.visitIincInsn(varIndex, increment);
}
@Override
public void visitTableSwitchInsn(int min, int max, Label dflt, Label... labels) {
instrumentReportCoverageInvocation();
super.visitTableSwitchInsn(min, max, dflt, labels);
}
@Override
public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels) {
instrumentReportCoverageInvocation();
super.visitLookupSwitchInsn(dflt, keys, labels);
}
@Override
public void visitMultiANewArrayInsn(String descriptor, int numDimensions) {
instrumentReportCoverageInvocation();
super.visitMultiANewArrayInsn(descriptor, numDimensions);
}
@Override
public AnnotationVisitor visitInsnAnnotation(
int typeRef, TypePath tp, String desc, boolean visible) {
instrumentReportCoverageInvocation();
return super.visitInsnAnnotation(typeRef, tp, desc, visible);
}
}
我使用了一个直截了当的类访问者
class CoverageClassVisitor extends ClassVisitor {
private String className;
CoverageClassVisitor(ClassVisitor cv) {
super(Opcodes.ASM9, cv);
}
@Override
public void visit(
int version, int acc, String name, String sig, String superName, String[] ifs) {
className = name;
super.visit(version, acc, name, sig, superName, ifs);
}
@Override
public MethodVisitor visitMethod(int access,
String name, String descriptor, String signature, String[] exceptions) {
return new CoverageMethodVisitor(
super.visitMethod(access, name, descriptor, signature, exceptions),
className,
name);
}
}
……以及下面的测试代码
public class ReportLineNumbers {
public static void main(String[] arg) throws IOException, IllegalAccessException {
String className = ReportLineNumbers.class.getName() + "$Example";
// ToolProvider.findFirst("javap")
// .ifPresent(p -> p.run(System.out, System.err, "-c", className));
ClassReader cr = new ClassReader(className);
ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
CoverageClassVisitor trans = new CoverageClassVisitor(cw);
cr.accept(trans, 0);
MethodHandles.lookup().defineClass(cw.toByteArray());
Example.method();
}
static class Example {
static void method() {
for(int i = 0; i < 3; i++) {
System.out.println(
i < 2?
new String(switch(i) {
case 0 -> {
// try {
yield "0";
// } catch(Throwable t) {
// yield "e";
// }
}
default -> {
for(int j = 1; j < 3; j++) {
System.out.println(j);
}
yield "3";
}
}):
new String(i == 2?
"4".toCharArray():
"5".toCharArray())
);
}
}
}
}
Example 类的设计尽可能具有挑战性，涵盖NEW 指令前后的不同分支类型(向前、向后、切换)。事实上，事实证明它是如此具有挑战性，以至于我不得不注释掉一个结构，就像 Eclipse 一样，即使没有转换器，它也会产生无效的字节码。但是当使用 javac 时，您可以启用这个内联的 try … catch … 构造，以查看转换器是否会正确处理它。
关于java - ASM 和 Javaagent 字节码检测 : ClassFormatError: StackMapTable format error: bad offset for Uninitialized，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/72877465/