Class CFG
- java.lang.Object
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- org.jboss.byteman.agent.adapter.cfg.CFG
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public class CFG extends Object
A control flow graph (cfg) for use by trigger method adapters. A trigger method adapter is required to notify the CFG each time an instruction or label is visited and each time a try catch block is notified. It is also required to notify the CFG when trigger code generation begins and ends. The cfg allows the trigger method adapter to identify whether or not trigger code is within the scope of one or more synchronized blocks, allowing it to protect the trigger call with try catch handlers which ensure that any open monitor enters are rounded off with a corresponding monitor exit. A cfg is constructed dynamically as the code is visited in order to enable trigger insertion to be performed during a single pass of the bytecode. SeeRuleTriggerMethodAdapter
for an example of how the methods provided by this class are invoked during visiting of the method byte code. Methods provided for driving CFG construction include:- non-control instruction visit:
add(int)
,add(int, int)
,add(int, int, int)
add(int, int[])
add(int, String)
,add(int, String, String, String)
,add(int, String, int)
, - control instruction visit:
split(org.objectweb.asm.Label)
,split(org.objectweb.asm.Label, org.objectweb.asm.Label)
,split(org.objectweb.asm.Label, org.objectweb.asm.Label, org.objectweb.asm.Label)
,split(org.objectweb.asm.Label, org.objectweb.asm.Label, org.objectweb.asm.Label[])
, - label visit:
visitLabel(org.objectweb.asm.Label)
, - try/catch block visit:
visitTryCatchBlock(org.objectweb.asm.Label, org.objectweb.asm.Label, org.objectweb.asm.Label, String)
, - trigger region demarcation:
visitTriggerStart(org.objectweb.asm.Label)
,visitTriggerEnd(org.objectweb.asm.Label)
, - code visit end demarcation:
visitMaxs()
,visitEnd()
,
Control flow graph model
The bytecode sequence is segmented into basic blocks at control flow branches ensuring there is no explicit control flow internal to a block. The only way normal control can flow from one block to another is via a switch/goto/branch instruction occuring at the end of the block. So, basic blocks are the nodes of the CFG and the links in the graph identify these control flow transitions.Normal control flow linkage is explicitly represented in the blocks as a list containing the labels of the target blocks. Labels are used rather than handles on the block themselves so that forward links to blocks which have not yet been generated can be modelled. Labels are resolved to the relevant block and instruction index as they are visited during walking of the bytecode.
The outgoing control flow link count can be obtained by calling methodBBlock.nOuts()
. The label of the block to which control is transferred can be identified by calling methodBBlock.nthOut(int)
. Note that valid link indices run from 1 to nOuts() (see below). Once a label has been visited it can be resolved to aCodeLocation
by calling methodgetLocation(org.objectweb.asm.Label)
. The returned value identifies both a block and an instruction offset in the block. Several caveats apply to this simple picture. Firstly, blocks ending in return or throw have no control flow -- they pass control back to the caller rather than to another basic block. So, the count returned byBBlock.nOuts()
will be 0 for such blocks. Secondly, all blocks except the last have a distinguished link which identifies the block successor link relationship. The successor block can be obtained by supplying value 0 as argument to methodBBlock.nthOut(int)
. This link is additional to any control flow links and it is not included in the count returned byBBlock.nOuts()
. Note that where there is a control flow link to the next block in line (e.g. where the block ends in an ifXX instruction) the label employed for the distinguished 0 link will also appear in the set of control flow links (as link 1 in the case of an ifXX instruction). The final caveat is that this graph model does not identify control flow which occurs as a consequence of generated exceptions.Exceptional Control Flow
Exception control flow is modelled independently from normal flow because it relates to a segment of the instruction sequence rather than individual instructions. A specific exception flow is associated with a each try catch block and the target of the flow is the start of the handler block. The cfg maintains a list ofTryCatchDetails
which identify the location of the try/catch start, its end and the associated handler start location. Once again labels are used so as to allow modelling of forward references to code locations which have not yet been generated. Note that handler start labels always refer to a code location which is at the start of a basic block. Start and end labels for a given try/catch block may refer to code locations offset into their containing basic block and possibly in distinct blocks. MethodstryCatchStart(org.objectweb.asm.Label)
,tryCatchEnd(org.objectweb.asm.Label)
andtryCatchHandlerStart(org.objectweb.asm.Label)
can be called to determine whether a given label identifies, respectively, the start of a try catch block, the end of a try catch block or the start of a handler block. MethodstryCatchStartDetails(org.objectweb.asm.Label)
tryCatchEndDetails(org.objectweb.asm.Label)
, andtryCatchHandlerStartDetails(org.objectweb.asm.Label)
can be used to retrieve the associatedTryCatchDetails
information.Label Resolution
The cfg relies upon its adapter client to notify it whenever a label is visited during a walk of the bytecode. This allows it to associate labels with the basic blocks and instruction offsets within those blocks. The cfg provides methodgetBlock(org.objectweb.asm.Label)
to resolve the primary label for a block (i.e. the one supplied as argument to a split call) to the associated block. It also provides methodgetBlockInstructionIdx(org.objectweb.asm.Label)
to resolve a label to aCodeLocation
i.e. block and instruction index within a block. Both methods return null if the label has not yet been visited. MethodgetContains(BBlock)
is also provided to obtain a list of all labels contained within a specific block. There may be more than one label which resolves to a location within a specific block. For example, the handler start label associated with a try/catch handler is contained in the handler block at offset 0 but is never the primary label for the block. Iteration over the contained set is used internally in the cfg to resolve equivalent labels.lock propagation algorithm
The cfg tracks the occurence of monitor enter and monitor exit instructions as they are encountered during the bytecode walk. Note that the relationship between enter and exit instructions is 1 to many. For any given monitor enter there are one or more exits associated with the normal control flow path and zero or more alternative exits associated with exception control flow paths. The association between monitor entry and monitor exit instructions is made available via methodsgetPairedEnter(CodeLocation)
, andgetPairedExit(CodeLocation, BBlock)
9note that a given enter will never have more than one exit in any given block). The cfg associates monitor enters and exits with their enclosing block, allowing it to identify the start and/or end of synchronized regions within a specific block. This information can be propagated along control flow links to identify outstanding monitor enters at any point in a given control flow path. Whenever a block is created it is associated with a set of open enter instructions i.e. enter instructions occurring along all control flow paths to the block for which no corresponding exit has been executed.- For the initial block the open enters list is empty.
- For a block reached by normal control flow the open enters list can be derived from any of the feed blocks
which transfer control to it. It is computed by adding and removing entries to/from the feed block's open
enters list according to the order the enters or exits appear in the block. Any feed block is valid because
every enter must have a single corresponding exit on each valid path through the bytecode. Two paths to the
same block cannot introduce different enters and exits without breaking this invariant. Also, enters and exits
must be strictly nested so the set of open monitors can be tracked using a simple stack model.
The algorithm propagates open enters along normal control flow paths whenever a split instruction is invoked
(splitting the instruction stream into a new block). The work is done in method
carryForward()
. This method identifies the current block's open enters list (how will emerge below), updates it with any enters and exits performed in the block and then, for each each outgoing control link, associates the new list with the linked block by inserting the list into a hash table keyed by the block label. Clearly, if the current block was itself arrived at via normal control flow then its open enters list will already be available in the hash table. Handler blocks require a different lookup. -
Computing the open enters list for a handler block which is the target of exception control flow is also done in
method
carryForward()
. This requires identifying all try/catch regions which enclose the block and tagging the correspondingTryCatchDetails
object with the location of any monitor enter instructions which are open at some point in the try catch region. If this is done for every block encountered during the bytecode walk then at the point where the handler block is split all enter instructions which are still open somewhere within the try/catch region will be listed in theTryCatchDetails
. So, at the split point the old block can be tested to see if it is labelled as a try/catch handler target and, if so, its open enters list can be looked up by locating theTryCatchDetails
associated with the handler start label.
- non-control instruction visit:
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Field Summary
Fields Modifier and Type Field Description static org.objectweb.asm.Type
EARLY_RETURN_EXCEPTION_TYPE
Type identifying return exceptions thrown by runtimestatic String
EARLY_RETURN_EXCEPTION_TYPE_NAME
name of type identifying return exceptions thrown by runtimestatic org.objectweb.asm.Type
EXECUTE_EXCEPTION_TYPE
Type identifying execute exceptions thrown by runtimestatic String
EXECUTE_EXCEPTION_TYPE_NAME
name of type identifying execute exceptions thrown by runtimestatic org.objectweb.asm.Type
THROW_EXCEPTION_TYPE
Type identifying throw exceptions thrown by runtimestatic String
THROW_EXCEPTION_TYPE_NAME
name of type identifying throw exceptions thrown by runtime
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
add(int instruction)
aopend an instruction to the current blockvoid
add(int instruction, int operand)
append an instruction with one operand to the current blockvoid
add(int instruction, int[] operands)
append an operand with more than two operands ot the current blockvoid
add(int instruction, int operand1, int operand2)
append an instruction with two operands to the current blockvoid
add(int instruction, String name)
append an instruction with a String operand to the current blockvoid
add(int instruction, String name, int dims)
append a multiarray create instruction to the current blockvoid
add(int instruction, String name, String desc)
append an invokedynamic instruction with 2 String operands to the current blockvoid
add(int instruction, String owner, String name, String desc)
append a field instruction with 3 String operands to the current blockvoid
add(int instruction, String owner, String name, String desc, boolean itf)
append a method instruction with 3 String operands and a boolean operand to the current blockBBlock
getBlock(org.objectweb.asm.Label label)
return the block containing a label if knownint
getBlockInstructionIdx(org.objectweb.asm.Label label)
return the index of the label in its enclosing block's instruction sequence or -1 if the label has not yet been visited.FanOut
getContains(BBlock block)
return a link object listing all the labels contained in a given blockCodeLocation
getLocation(org.objectweb.asm.Label label)
return the location of the label if known or null if it has not yet been reached.String
getName(int nameIdx)
List<CodeLocation>
getOpenMonitorEnters(BBlock block)
retrieve the list of monitor enter locations open at the start of a given blockList<CodeLocation>
getOpenMonitorEnters(org.objectweb.asm.Label label)
retrieve the list of monitor enter locations open at the start of a given blockIterator<CodeLocation>
getOpenMonitors(TriggerDetails triggerDetails)
retrieve the list of monitor enter locations associated with a trigger block.CodeLocation
getPairedEnter(CodeLocation exit)
locate the monitor enter instruction associated with a given monitor exitint
getSavedMonitorIdx(CodeLocation open)
return the index of the local var at which this monitorenter saved its lock objectboolean
hasLocation(org.objectweb.asm.Label label)
test whether the location of a label is known yetboolean
inBytemanHandler()
check if the current block is a byteman-generated handler i.e.boolean
inBytemanTrigger()
check if the current block is a byteman-generated trigger section.boolean
inOpenMonitor()
test whether there are any open monitorenters with no corresponding monitorexit on a path to the current instructionboolean
inRethrowHandler()
return true if the current block is a rethrow handler i.e.CodeLocation
nextLocation()
return a location which will identify the next instruction added to the current blockCodeLocation
setLocation(org.objectweb.asm.Label label)
set the location of a label to the next instruction offset in the current blockvoid
split(org.objectweb.asm.Label newStart)
split the graph at a control-flow dead-end using the label provided to identify the new current block.void
split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label out)
split the graph at a control-flow goto point using the labels provided to identify the new current block and the goto target.void
split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label out, org.objectweb.asm.Label out2)
split the graph at a control-flow if branch point using the labels provided to identify the new current block the if branch target and the else branch target.void
split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label dflt, org.objectweb.asm.Label[] labels)
split the graph at a control-flow switch branch point using the labels provided to identify the new current block, the switch case default branch target and the rest of the switch case branch targets.String
toString()
generate a string representation of the CFGIterator<TriggerDetails>
triggerDetails()
return an iterator ovver all known trigger detailsboolean
triggerEnd(org.objectweb.asm.Label label)
test if a label marks the end of a trigger blockTriggerDetails
triggerEndDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which end at this labelboolean
triggerStart(org.objectweb.asm.Label label)
test if a label marks the start of a trigger blockTriggerDetails
triggerStartDetails(org.objectweb.asm.Label label)
return details of any trigger block which starts at this labelboolean
tryCatchEnd(org.objectweb.asm.Label label)
test if a label marks the end of a try catch blockList<TryCatchDetails>
tryCatchEndDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which end at this labelboolean
tryCatchHandlerStart(org.objectweb.asm.Label label)
test if a label marks the start of the handler for a try catch blockList<TryCatchDetails>
tryCatchHandlerStartDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks whose handler starts at this labelboolean
tryCatchStart(org.objectweb.asm.Label label)
test if a label marks the start of a try catch blockList<TryCatchDetails>
tryCatchStartDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which start at this labelvoid
visitEnd()
void
visitLabel(org.objectweb.asm.Label label)
notify the CFG that a label has been visited by the method visitor and hence its position will now be resolvedvoid
visitMaxs()
this can be called when the code generator call visiMaxs but it does nothing just nowvoid
visitTriggerEnd(org.objectweb.asm.Label label)
notify the CFG that a label which represents the end of a trigger injection sequence has just been visited by the method visitor.void
visitTriggerStart(org.objectweb.asm.Label label)
notify the CFG that a label which represents the start of a trigger injection sequence has just been visited by the method visitor.void
visitTryCatchBlock(org.objectweb.asm.Label start, org.objectweb.asm.Label end, org.objectweb.asm.Label handler, String type)
notify the CFG of the location of a try catch block.
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Field Detail
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EXECUTE_EXCEPTION_TYPE
public static final org.objectweb.asm.Type EXECUTE_EXCEPTION_TYPE
Type identifying execute exceptions thrown by runtime
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EARLY_RETURN_EXCEPTION_TYPE
public static final org.objectweb.asm.Type EARLY_RETURN_EXCEPTION_TYPE
Type identifying return exceptions thrown by runtime
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THROW_EXCEPTION_TYPE
public static final org.objectweb.asm.Type THROW_EXCEPTION_TYPE
Type identifying throw exceptions thrown by runtime
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EXECUTE_EXCEPTION_TYPE_NAME
public static final String EXECUTE_EXCEPTION_TYPE_NAME
name of type identifying execute exceptions thrown by runtime
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EARLY_RETURN_EXCEPTION_TYPE_NAME
public static final String EARLY_RETURN_EXCEPTION_TYPE_NAME
name of type identifying return exceptions thrown by runtime
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THROW_EXCEPTION_TYPE_NAME
public static final String THROW_EXCEPTION_TYPE_NAME
name of type identifying throw exceptions thrown by runtime
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Constructor Detail
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CFG
public CFG(String methodName, org.objectweb.asm.Label start)
construct a CFG labelling the initial block with a given label- Parameters:
methodName
- the name of the method fro which this is a CFGstart
- a label for the entry block of the CFG
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Method Detail
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add
public void add(int instruction)
aopend an instruction to the current block- Parameters:
instruction
- the instruction to be appended
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add
public void add(int instruction, int operand)
append an instruction with one operand to the current block- Parameters:
instruction
- the instruction to be appendedoperand
- the instruction's operand
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add
public void add(int instruction, int operand1, int operand2)
append an instruction with two operands to the current block- Parameters:
instruction
- the instruction to be appendedoperand1
- the instruction's first operandoperand2
- the instruction's second operand
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add
public void add(int instruction, int[] operands)
append an operand with more than two operands ot the current block- Parameters:
instruction
- the instruction to be appendedoperands
- the instruction's operands
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add
public void add(int instruction, String name)
append an instruction with a String operand to the current block- Parameters:
instruction
- the instruction to be appendedname
- the String operand
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add
public void add(int instruction, String name, int dims)
append a multiarray create instruction to the current block- Parameters:
instruction
- the instruction to be appendedname
- the name of the array base typedims
- the number of array dimensions
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add
public void add(int instruction, String name, String desc)
append an invokedynamic instruction with 2 String operands to the current block- Parameters:
instruction
- the invokedynamic instruction to be appendedname
- the first String operanddesc
- the second String operand
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add
public void add(int instruction, String owner, String name, String desc)
append a field instruction with 3 String operands to the current block- Parameters:
instruction
- the instruction to be appendedowner
- the first String operandname
- the second String operanddesc
- the third String operand
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add
public void add(int instruction, String owner, String name, String desc, boolean itf)
append a method instruction with 3 String operands and a boolean operand to the current block- Parameters:
instruction
- the instruction to be appendedowner
- the first String operandname
- the second String operanddesc
- the third String operanditf
- the boolean operand
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setLocation
public CodeLocation setLocation(org.objectweb.asm.Label label)
set the location of a label to the next instruction offset in the current block- Parameters:
label
- the label whose location is to be set- Returns:
- the resulting CodeLocation
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getLocation
public CodeLocation getLocation(org.objectweb.asm.Label label)
return the location of the label if known or null if it has not yet been reached. note that if this returns non-null then the label's offset in the generated bytecode can be safely retrieved but if it returns null then attempting to retrieve the offset will generate an exception.- Parameters:
label
- the label whose location is desired- Returns:
- the label's location if it has been reached otherwise null
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hasLocation
public boolean hasLocation(org.objectweb.asm.Label label)
test whether the location of a label is known yet- Parameters:
label
- the label whose location is desired- Returns:
- true if the label's location has been reached otherwise false
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nextLocation
public CodeLocation nextLocation()
return a location which will identify the next instruction added to the current block- Returns:
- the location of the next instruction added to the current block
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getBlock
public BBlock getBlock(org.objectweb.asm.Label label)
return the block containing a label if known- Parameters:
label
- the label whose containing block is desired- Returns:
- the label's location if it has been reached otherwise null
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getContains
public FanOut getContains(BBlock block)
return a link object listing all the labels contained in a given block- Parameters:
block
- the block whose labels are being sought- Returns:
- the associated set of labels
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getOpenMonitorEnters
public List<CodeLocation> getOpenMonitorEnters(org.objectweb.asm.Label label)
retrieve the list of monitor enter locations open at the start of a given block- Parameters:
label
- the label of the block- Returns:
- the list of open monitor enter locations
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getOpenMonitorEnters
public List<CodeLocation> getOpenMonitorEnters(BBlock block)
retrieve the list of monitor enter locations open at the start of a given block- Parameters:
block
- the block- Returns:
- the list of open monitor enter locations in reverse order of appearance in the bytecode
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getOpenMonitors
public Iterator<CodeLocation> getOpenMonitors(TriggerDetails triggerDetails)
retrieve the list of monitor enter locations associated with a trigger block. this is called when we are inserting try catch handlers for trigger locations to determine whether they need to perform any monitor exit operations before executing the normal trigger exception handling code.- Parameters:
triggerDetails
- the trigger being checked- Returns:
- the list of locations for monitor enters open at the trigger start
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getPairedEnter
public CodeLocation getPairedEnter(CodeLocation exit)
locate the monitor enter instruction associated with a given monitor exit- Parameters:
exit
- the location of the monitor exit- Returns:
- the paired enter
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getSavedMonitorIdx
public int getSavedMonitorIdx(CodeLocation open)
return the index of the local var at which this monitorenter saved its lock object- Parameters:
open
- the location of th emonitor enter- Returns:
- the var index
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inOpenMonitor
public boolean inOpenMonitor()
test whether there are any open monitorenters with no corresponding monitorexit on a path to the current instruction- Returns:
- true if there are open monitorenters otherwise false
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split
public void split(org.objectweb.asm.Label newStart)
split the graph at a control-flow dead-end using the label provided to identify the new current block. the caller is obliged to call visitLabel immediately after calling this method to ensure that the current block label is indexed appropriately.- Parameters:
newStart
- the label to be used to identify the new current block
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split
public void split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label out)
split the graph at a control-flow goto point using the labels provided to identify the new current block and the goto target. the caller is obliged to call visitLabel immediately after calling this method to ensure that the current block label is indexed appropriately.- Parameters:
newStart
- the label to be used to identify the new current blockout
- the target of the GOTO
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split
public void split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label out, org.objectweb.asm.Label out2)
split the graph at a control-flow if branch point using the labels provided to identify the new current block the if branch target and the else branch target. the caller is obliged to call visitLabel immediately after calling this method to ensure that the current block label is indexed appropriately.- Parameters:
newStart
- the label to be used to identify the new current blockout
- the target of the if branchout2
- the target of the else branch which probably ought to be the same label as passed for the current block (IF instructions assume drop-through)
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split
public void split(org.objectweb.asm.Label newStart, org.objectweb.asm.Label dflt, org.objectweb.asm.Label[] labels)
split the graph at a control-flow switch branch point using the labels provided to identify the new current block, the switch case default branch target and the rest of the switch case branch targets. the caller is obliged to call visitLabel immediately after calling this method to ensure that the current block label is indexed appropriately.- Parameters:
newStart
- the label to be used to identify the new current blockdflt
- the switch case default branch targetlabels
- the other switch case branch targets
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tryCatchStart
public boolean tryCatchStart(org.objectweb.asm.Label label)
test if a label marks the start of a try catch block- Parameters:
label
- the label to be tested- Returns:
- true if the label marks the start of a try catch block otherwise false
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tryCatchEnd
public boolean tryCatchEnd(org.objectweb.asm.Label label)
test if a label marks the end of a try catch block- Parameters:
label
- the label to be tested- Returns:
- true if the label marks the start of a try catch block otherwise false
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tryCatchHandlerStart
public boolean tryCatchHandlerStart(org.objectweb.asm.Label label)
test if a label marks the start of the handler for a try catch block- Parameters:
label
- the label to be tested- Returns:
- true if the label marks the start of a try catch block otherwise false
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tryCatchStartDetails
public List<TryCatchDetails> tryCatchStartDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which start at this label- Parameters:
label
- the start label- Returns:
- list of try catch block details
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tryCatchEndDetails
public List<TryCatchDetails> tryCatchEndDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which end at this label- Parameters:
label
- the end label- Returns:
- list of try catch block details
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tryCatchHandlerStartDetails
public List<TryCatchDetails> tryCatchHandlerStartDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks whose handler starts at this label- Parameters:
label
- the handler start label- Returns:
- list of try catch block details
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triggerStart
public boolean triggerStart(org.objectweb.asm.Label label)
test if a label marks the start of a trigger block- Parameters:
label
- the label to be tested- Returns:
- true if the label marks the start of a trigger block otherwise false
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triggerEnd
public boolean triggerEnd(org.objectweb.asm.Label label)
test if a label marks the end of a trigger block- Parameters:
label
- the label to be tested- Returns:
- true if the label marks the start of a trigger block otherwise false
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triggerStartDetails
public TriggerDetails triggerStartDetails(org.objectweb.asm.Label label)
return details of any trigger block which starts at this label- Parameters:
label
- the label- Returns:
- trigger start details
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triggerEndDetails
public TriggerDetails triggerEndDetails(org.objectweb.asm.Label label)
return the list of details of try catch blocks which end at this label- Parameters:
label
- the label- Returns:
- trigger end details
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triggerDetails
public Iterator<TriggerDetails> triggerDetails()
return an iterator ovver all known trigger details- Returns:
- the iterator
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visitLabel
public void visitLabel(org.objectweb.asm.Label label)
notify the CFG that a label has been visited by the method visitor and hence its position will now be resolved- Parameters:
label
- the label being visited
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visitTriggerStart
public void visitTriggerStart(org.objectweb.asm.Label label)
notify the CFG that a label which represents the start of a trigger injection sequence has just been visited by the method visitor.- Parameters:
label
- the label being visited
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visitTriggerEnd
public void visitTriggerEnd(org.objectweb.asm.Label label)
notify the CFG that a label which represents the end of a trigger injection sequence has just been visited by the method visitor.- Parameters:
label
- the label being visited
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visitTryCatchBlock
public void visitTryCatchBlock(org.objectweb.asm.Label start, org.objectweb.asm.Label end, org.objectweb.asm.Label handler, String type)
notify the CFG of the location of a try catch block. note that this does not mean that the code generator has been notified of this information. these are normally notified to the method visitor before visiting the code. this is problematic if we want to insert our trigger point try catch blocks because we need to order them before any enclosing try catch blocks with wider scope. so the method visitor calls this routine up front but only notifies the try catch block to its super when the end label for the try catch block is reached.- Parameters:
start
- the block start labelend
- the block end labelhandler
- the block handler labeltype
- handled exception type name
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inBytemanHandler
public boolean inBytemanHandler()
check if the current block is a byteman-generated handler i.e. one which was created to catch an exception thrown by the byteman runtime. n.b. a byteman handler only ever spans one block.- Returns:
- true if the current block is a byteman-generated handler
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inRethrowHandler
public boolean inRethrowHandler()
return true if the current block is a rethrow handler i.e. one which was created to close a monitor exit instruction and then rethrow an exception. n.b. this must only be called when the next instruction to be added to the byetcode sequence is an ATHROW- Returns:
- true if the current block is a rethrow handler
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inBytemanTrigger
public boolean inBytemanTrigger()
check if the current block is a byteman-generated trigger section. this can be checked by testing whether there is an open try catch for one of the Byteman exception types- Returns:
- true if the current block is a byteman-generated trigger section
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visitMaxs
public void visitMaxs()
this can be called when the code generator call visiMaxs but it does nothing just now
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visitEnd
public void visitEnd()
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toString
public String toString()
generate a string representation of the CFG
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getBlockInstructionIdx
public int getBlockInstructionIdx(org.objectweb.asm.Label label)
return the index of the label in its enclosing block's instruction sequence or -1 if the label has not yet been visited. the index can be used to lookup the insruction following the label.- Parameters:
label
- the label whose index is sought- Returns:
- the known label index or -1 if unknown
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getName
public String getName(int nameIdx)
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