asm-util 9.6 · org.objectweb.asm.util.CheckFrameAnalyzer

An Analyzer subclass which checks that methods provide stack map frames where expected (i.e. at jump target and after instructions without immediate successor), and that these stack map frames are valid (for the provided interpreter; they may still be invalid for the JVM, if the Interpreter uses a simplified type system compared to the JVM verifier). This is done in two steps:

First, the stack map frames in FrameNodes are expanded, and stored at their respective instruction offsets. The expansion process uncompresses the APPEND, CHOP and SAME frames to FULL frames. It also converts the stack map frame verification types to Values, via the provided Interpreter. The expansion is done in expandFrames, by looking at each FrameNode in sequence (compressed frames are defined relatively to the previous FrameNode, or the implicit first frame). The actual decompression is done in expandFrame, and the type conversion in newFrameValue.
Next, the method instructions are checked in sequence. Starting from the implicit initial frame, the execution of each instruction i is simulated on the current stack map frame, with the Frame#execute method. This gives a new stack map frame f, representing the stack map frame state after the execution of i. Then:
- If there is a next instruction and if the control flow cannot continue to it (e.g. if i is a RETURN or an ATHROW, for instance): an existing stack map frame f0 (coming from the first step) is expected after i.
- If there is a next instruction and if the control flow can continue to it (e.g. if i is a ALOAD, for instance): either there an existing stack map frame f0 (coming from the first step) after i, or there is none. In the first case f and f0 must be compatible: the types in f must be sub types of the corresponding types in the existing frame f0 (otherwise an exception is thrown). In the second case, f0 is simply set to the value of f.
- If the control flow can continue to some instruction j (e.g. if i is an IF_EQ, for instance): an existing stack map frame f0 (coming from the first step) is expected at j, which must be compatible with f (as defined previously).
The sequential loop over the instructions is done in init, which is called from the Analyzer#analyze method. Cases where the control flow cannot continue to the next instruction are handled in endControlFlow. Cases where the control flow can continue to the next instruction, or jump to another instruction, are handled in checkFrame. This method checks that an existing stack map frame is present when required, and checks the stack map frames compatibility with checkMerge.

Field Summary

Modifier and Type	Field and Description
private int	currentLocals The number of locals in the last stack map frame processed by `expandFrame`.
private InsnList	insnList Hides org.objectweb.asm.tree.analysis.Analyzer.insnList. The instructions of the currently analyzed method.
private final Interpreter<V>	interpreter Hides org.objectweb.asm.tree.analysis.Analyzer.interpreter. The interpreter to use to symbolically interpret the bytecode instructions.

Access	Constructor and Description
pack-priv	CheckFrameAnalyzer(final Interpreter<V> interpreter)

Method Summary

Modifier and Type	Method and Description
private void	checkFrame(final int an instruction index. insnIndex, final Frame<V> a frame. This frame is left unchanged by this method. frame, final boolean whether a frame must already exist or not in `frames` at 'insnIndex'. requireFrame) Checks that the given frame is compatible with the frame at the given instruction index, if any.
private String	Returns: an error message if the frames have incompatible sizes, or if a type in the source frame is not a sub type of the corresponding type in the destination frame. Returns null otherwise. checkMerge(final Frame<V> a source frame. This frame is left unchanged by this method. srcFrame, final Frame<V> a destination frame. This frame is left unchanged by this method. dstFrame) Checks that merging the two given frames would not produce any change, i.e. that the types in the source frame are sub types of the corresponding types in the destination frame.
private void	endControlFlow(final int an instruction index. insnIndex) Ends the control flow graph at the given instruction.
private Frame<V>	Returns: the expanded version of 'frameNode'. expandFrame(final String the internal name of the class to which 'frameNode' belongs. owner, final Frame<V> the frame before 'frameNode', in expanded form. previousFrame, final FrameNode a possibly compressed stack map frame. frameNode) Returns the expanded representation of the given `FrameNode`.
private void	expandFrames(final String the internal name of the class to which 'method' belongs. owner, final MethodNode the method whose frames must be expanded. method, final Frame<V> the implicit initial frame of 'method'. initialFrame) Expands the `FrameNode` "instructions" of the given method into `Frame` objects and stores them at the corresponding indices of the `frames` array.
private boolean	Returns: true if 'insnIndex' is followed by a JVM instruction or a by stack map frame. hasNextJvmInsnOrFrame(final int an instruction index. insnIndex) Returns true if the given instruction is followed by a JVM instruction or a by stack map frame.
protected void	init(final String the internal name of the class to which the method belongs (see `Type#getInternalName()`). owner, final MethodNode the method to be analyzed. method) Overrides org.objectweb.asm.tree.analysis.Analyzer.init. Initializes this analyzer.
private static boolean	Returns: true except for label, line number and stack map frame nodes. isJvmInsnNode(final AbstractInsnNode an instruction node. insnNode) Returns true if the given instruction node corresponds to a real JVM instruction.
private V	Returns: a value that represents the given type. newFrameValue(final String the internal name of the class to which 'frameNode' belongs. owner, final FrameNode the stack map frame to which 'type' belongs. frameNode, final Object an Integer, String or LabelNode object representing a primitive, reference or uninitialized a stack map frame type, respectively. See `FrameNode`. type) Creates a new `Value` that represents the given stack map frame type.

Inherited from org.objectweb.asm.tree.analysis.Analyzer:: analyze analyzeAndComputeMaxs getFrames getHandlers newControlFlowEdge newControlFlowExceptionEdge newControlFlowExceptionEdge newFrame newFrame

Field Detail

currentLocals	back to summary
private int currentLocals The number of locals in the last stack map frame processed by `expandFrame`. Long and double values are represented with two elements.

insnList	back to summary
private InsnList insnList Hides org.objectweb.asm.tree.analysis.Analyzer.insnList. The instructions of the currently analyzed method.

insnList

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private InsnList insnList

Hides org.objectweb.asm.tree.analysis.Analyzer.insnList.

The instructions of the currently analyzed method.

interpreter	back to summary
private final Interpreter<V> interpreter Hides org.objectweb.asm.tree.analysis.Analyzer.interpreter. The interpreter to use to symbolically interpret the bytecode instructions.

interpreter

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private final Interpreter<V> interpreter

Hides org.objectweb.asm.tree.analysis.Analyzer.interpreter.

The interpreter to use to symbolically interpret the bytecode instructions.

Constructor Detail

CheckFrameAnalyzer	back to summary
pack-priv CheckFrameAnalyzer(final Interpreter<V> interpreter)

Method Detail

checkFrame back to summary

checkFrame	back to summary
private void checkFrame(final int insnIndex, final Frame<V> frame, final boolean requireFrame) throws AnalyzerException Checks that the given frame is compatible with the frame at the given instruction index, if any. If there is no frame at this instruction index and none is required, the frame at 'insnIndex' is set to the given frame. Otherwise, if the merge of the two frames is not equal to the current frame at 'insnIndex', an exception is thrown. Parameters insnIndex:int an instruction index. frame:Frame<V> a frame. This frame is left unchanged by this method. requireFrame:boolean whether a frame must already exist or not in `frames` at 'insnIndex'. Exceptions AnalyzerException: if the frames have incompatible sizes or if the frame at 'insnIndex' is missing (if required) or not compatible with 'frame'.

private void checkFrame(final int insnIndex, final Frame<V> frame, final boolean requireFrame) throws AnalyzerException

Checks that the given frame is compatible with the frame at the given instruction index, if any. If there is no frame at this instruction index and none is required, the frame at 'insnIndex' is set to the given frame. Otherwise, if the merge of the two frames is not equal to the current frame at 'insnIndex', an exception is thrown.

Parameters

insnIndex:int: an instruction index.
frame:Frame<V>: a frame. This frame is left unchanged by this method.
requireFrame:boolean: whether a frame must already exist or not in frames at 'insnIndex'.

Exceptions

AnalyzerException:: if the frames have incompatible sizes or if the frame at 'insnIndex' is missing (if required) or not compatible with 'frame'.

checkMerge	back to summary
private String checkMerge(final Frame<V> srcFrame, final Frame<V> dstFrame) Checks that merging the two given frames would not produce any change, i.e. that the types in the source frame are sub types of the corresponding types in the destination frame. Parameters srcFrame:Frame<V> a source frame. This frame is left unchanged by this method. dstFrame:Frame<V> a destination frame. This frame is left unchanged by this method. Returns:String an error message if the frames have incompatible sizes, or if a type in the source frame is not a sub type of the corresponding type in the destination frame. Returns null otherwise.

checkMerge

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private String checkMerge(final Frame<V> srcFrame, final Frame<V> dstFrame)

Checks that merging the two given frames would not produce any change, i.e. that the types in the source frame are sub types of the corresponding types in the destination frame.

Parameters

srcFrame:Frame<V>: a source frame. This frame is left unchanged by this method.
dstFrame:Frame<V>: a destination frame. This frame is left unchanged by this method.

Returns:String

an error message if the frames have incompatible sizes, or if a type in the source frame is not a sub type of the corresponding type in the destination frame. Returns null otherwise.

endControlFlow back to summary

endControlFlow	back to summary
private void endControlFlow(final int insnIndex) throws AnalyzerException Ends the control flow graph at the given instruction. This method checks that there is an existing frame for the next instruction, if any. Parameters insnIndex:int an instruction index. Exceptions AnalyzerException: if 'insnIndex' is not the last instruction and there is no frame at 'insnIndex' + 1 in `getFrames`.

private void endControlFlow(final int insnIndex) throws AnalyzerException

Ends the control flow graph at the given instruction. This method checks that there is an existing frame for the next instruction, if any.

Parameters

insnIndex:int: an instruction index.

Exceptions

AnalyzerException:: if 'insnIndex' is not the last instruction and there is no frame at 'insnIndex' + 1 in getFrames.

expandFrame back to summary

expandFrame	back to summary
private Frame<V> expandFrame(final String owner, final Frame<V> previousFrame, final FrameNode frameNode) throws AnalyzerException Returns the expanded representation of the given `FrameNode`. Parameters owner:String the internal name of the class to which 'frameNode' belongs. previousFrame:Frame<V> the frame before 'frameNode', in expanded form. frameNode:FrameNode a possibly compressed stack map frame. Returns:Frame<V> the expanded version of 'frameNode'. Exceptions AnalyzerException: if 'frameNode' is invalid.

private Frame<V> expandFrame(final String owner, final Frame<V> previousFrame, final FrameNode frameNode) throws AnalyzerException

Returns the expanded representation of the given FrameNode.

Parameters

owner:String: the internal name of the class to which 'frameNode' belongs.
previousFrame:Frame<V>: the frame before 'frameNode', in expanded form.
frameNode:FrameNode: a possibly compressed stack map frame.

Returns:Frame<V>

the expanded version of 'frameNode'.

Exceptions

AnalyzerException:: if 'frameNode' is invalid.

expandFrames back to summary

expandFrames	back to summary
private void expandFrames(final String owner, final MethodNode method, final Frame<V> initialFrame) throws AnalyzerException Expands the `FrameNode` "instructions" of the given method into `Frame` objects and stores them at the corresponding indices of the `frames` array. The expanded frames are also associated with the label and line number nodes immediately preceding each frame node. Parameters owner:String the internal name of the class to which 'method' belongs. method:MethodNode the method whose frames must be expanded. initialFrame:Frame<V> the implicit initial frame of 'method'. Exceptions AnalyzerException: if the stack map frames of 'method', i.e. its FrameNode "instructions", are invalid.

private void expandFrames(final String owner, final MethodNode method, final Frame<V> initialFrame) throws AnalyzerException

Expands the FrameNode "instructions" of the given method into Frame objects and stores them at the corresponding indices of the frames array. The expanded frames are also associated with the label and line number nodes immediately preceding each frame node.

Parameters

owner:String: the internal name of the class to which 'method' belongs.
method:MethodNode: the method whose frames must be expanded.
initialFrame:Frame<V>: the implicit initial frame of 'method'.

Exceptions

AnalyzerException:: if the stack map frames of 'method', i.e. its FrameNode "instructions", are invalid.

hasNextJvmInsnOrFrame	back to summary
private boolean hasNextJvmInsnOrFrame(final int insnIndex) Returns true if the given instruction is followed by a JVM instruction or a by stack map frame. Parameters insnIndex:int an instruction index. Returns:boolean true if 'insnIndex' is followed by a JVM instruction or a by stack map frame.

hasNextJvmInsnOrFrame

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private boolean hasNextJvmInsnOrFrame(final int insnIndex)

Returns true if the given instruction is followed by a JVM instruction or a by stack map frame.

Parameters

insnIndex:int: an instruction index.

Returns:boolean

true if 'insnIndex' is followed by a JVM instruction or a by stack map frame.

init back to summary

init	back to summary
protected void init(final String owner, final MethodNode method) throws AnalyzerException Overrides org.objectweb.asm.tree.analysis.Analyzer.init. Doc from org.objectweb.asm.tree.analysis.Analyzer.init. Initializes this analyzer. This method is called just before the execution of control flow analysis loop in `analyze`. The default implementation of this method does nothing. Parameters owner:String the internal name of the class to which the method belongs (see `Type#getInternalName()`). method:MethodNode the method to be analyzed. Annotations @Override Exceptions AnalyzerException: if a problem occurs.

protected void init(final String owner, final MethodNode method) throws AnalyzerException

Overrides org.objectweb.asm.tree.analysis.Analyzer.init.

Doc from org.objectweb.asm.tree.analysis.Analyzer.init.

Initializes this analyzer. This method is called just before the execution of control flow analysis loop in analyze. The default implementation of this method does nothing.

Parameters

owner:String: the internal name of the class to which the method belongs (see Type#getInternalName()).
method:MethodNode: the method to be analyzed.

Annotations

@Override

Exceptions

AnalyzerException:: if a problem occurs.

isJvmInsnNode	back to summary
private static boolean isJvmInsnNode(final AbstractInsnNode insnNode) Returns true if the given instruction node corresponds to a real JVM instruction. Parameters insnNode:AbstractInsnNode an instruction node. Returns:boolean true except for label, line number and stack map frame nodes.

isJvmInsnNode

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private static boolean isJvmInsnNode(final AbstractInsnNode insnNode)

Returns true if the given instruction node corresponds to a real JVM instruction.

Parameters

insnNode:AbstractInsnNode: an instruction node.

Returns:boolean

true except for label, line number and stack map frame nodes.

newFrameValue back to summary

newFrameValue	back to summary
private V newFrameValue(final String owner, final FrameNode frameNode, final Object type) throws AnalyzerException Creates a new `Value` that represents the given stack map frame type. Parameters owner:String the internal name of the class to which 'frameNode' belongs. frameNode:FrameNode the stack map frame to which 'type' belongs. type:Object an Integer, String or LabelNode object representing a primitive, reference or uninitialized a stack map frame type, respectively. See `FrameNode`. Returns:V a value that represents the given type. Exceptions AnalyzerException: if 'type' is an invalid stack map frame type.

private V newFrameValue(final String owner, final FrameNode frameNode, final Object type) throws AnalyzerException

Creates a new Value that represents the given stack map frame type.

Parameters

owner:String: the internal name of the class to which 'frameNode' belongs.
frameNode:FrameNode: the stack map frame to which 'type' belongs.
type:Object: an Integer, String or LabelNode object representing a primitive, reference or uninitialized a stack map frame type, respectively. See FrameNode.

Returns:V

a value that represents the given type.

Exceptions

AnalyzerException:: if 'type' is an invalid stack map frame type.

pack-priv Class CheckFrameAnalyzer<V extends org.objectweb.asm.tree.analysis.Value>

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail