My instances function similarly to instances of MethodContext, but they hold the dynamic state for execution of a block in Smalltalk. They access all temporary variables and the method sender via their home pointer, so that those values are effectively shared. Their indexable part is used to store their independent value stack during execution.

My instance must hold onto its home in order to work. This can cause circularities if the home is also pointing (via a temp, perhaps) to the instance. In the rare event that this happens (as in SortedCollection sortBlock:) the message fixTemps will replace home with a copy of home, thus defeating the sharing of temps but, nonetheless, eliminating the circularity.

BlockContexts must only be created using the method newForMethod:. Note that it is impossible to determine the real object size of a BlockContext except by asking for the frameSize of its method. Any fields above the stack pointer (stackp) are truly invisible -- even (and especially!) to the garbage collector. Any store into stackp other than by the primitive method stackp: is potentially fatal.

	Worlds

	accessing
	copyForSaving fixTemps hasInstVarRef hasMethodReturn home method numArgs receiver tempAt: tempAt:put:

	controlling
	repeat repeatWithGCIf: whileFalse whileFalse: whileTrue whileTrue:

	evaluating
	ifError: timeToRun value value: value:ifError: value:value: value:value:value: value:value:value:value: valueWithArguments:

	exceptions
	assert ensure: ifCurtailed: on:do:

	initialize-release
	home:startpc:nargs:

	instruction decoding
	blockReturnTop

	printing
	printOn: printOnStream:

	private
	aboutToReturn:through: cannotReturn: instVarAt:put: startpc valueError valueUnpreemptively

	private-debugger
	hideFromDebugger

	private-exceptions
	ifProperUnwindSupportedElseSignalAboutToReturn valueUninterruptably

	scheduling
	fork forkAt: newProcess newProcessWith:

	system simulation
	pushArgs:from: stepToSendOrReturn

	tiles
	valueWithPossibleArgs:

	Camp Smalltalk	top
	sunitEnsure:
	sunitOn:do:

Worlds

top

	accessing	top
	copyForSaving Fix the values of the temporary variables used in the block that are ordinarily shared with the method in which the block is defined.
	fixTemps Fix the values of the temporary variables used in the block that are ordinarily shared with the method in which the block is defined.
	hasInstVarRef Answer whether the receiver references an instance variable.
	hasMethodReturn Answer whether the receiver has a return ('^') in its code.
	home Answer the context in which the receiver was defined.
	method Answer the compiled method in which the receiver was defined.
	numArgs Answer the number of arguments that must be used to evaluate this block
	receiver Refer to the comment in ContextPart|receiver.
	tempAt: Refer to the comment in ContextPart|tempAt:.
	tempAt:put: Refer to the comment in ContextPart|tempAt:put:.

	controlling	top
	repeat Evaluate the receiver repeatedly, ending only if the block explicitly returns.
	repeatWithGCIf: run the receiver, and if testBlock returns true, garbage collect and run the receiver again
	whileFalse Ordinarily compiled in-line, and therefore not overridable. This is in case the message is sent to other than a literal block. Evaluate the receiver, as long as its value is false.
	whileFalse: Ordinarily compiled in-line, and therefore not overridable. This is in case the message is sent to other than a literal block. Evaluate the argument, aBlock, as long as the value of the receiver is false.
	whileTrue Ordinarily compiled in-line, and therefore not overridable. This is in case the message is sent to other than a literal block. Evaluate the receiver, as long as its value is true.
	whileTrue: Ordinarily compiled in-line, and therefore not overridable. This is in case the message is sent to other than a literal block. Evaluate the argument, aBlock, as long as the value of the receiver is true.

	evaluating	top
	ifError: Evaluate the block represented by the receiver, and normally return it's value. If an error occurs, the errorHandlerBlock is evaluated, and it's value is instead returned. The errorHandlerBlock must accept either no parameters, or two (the error message and the receiver). The receiver should not contain an explicit return statement as this would leave an obsolete error handler hanging around.
	timeToRun Answer the number of milliseconds taken to execute this block.
	value Primitive. Evaluate the block represented by the receiver. Fail if the block expects any arguments or if the block is already being executed. Optional. No Lookup. See Object documentation whatIsAPrimitive.
	value: Primitive. Evaluate the block represented by the receiver. Fail if the block expects other than one argument or if the block is already being executed. Optional. No Lookup. See Object documentation whatIsAPrimitive.
	value:ifError: Evaluate the block represented by the receiver. If an error occurs aBlock is evaluated with the error message and the receiver as parameters. The receiver should not contain an explicit return statement as this would leave an obsolete error handler hanging around.
	value:value: Primitive. Evaluate the block represented by the receiver. Fail if the block expects other than two arguments or if the block is already being executed. Optional. See Object documentation whatIsAPrimitive.
	value:value:value: Primitive. Evaluate the block represented by the receiver. Fail if the block expects other than three arguments or if the block is already being executed. Optional. See Object documentation whatIsAPrimitive.
	value:value:value:value: Primitive. Evaluate the block represented by the receiver. Fail if the block expects other than three arguments or if the block is already being executed. Optional. See Object documentation whatIsAPrimitive.
	valueWithArguments: Primitive. Evaluate the block represented by the receiver. The argument is an Array whose elements are the arguments for the block. Fail if the length of the Array is not the same as the the number of arguments that the block was expecting. Fail if the block is already being executed. Essential. See Object documentation whatIsAPrimitive.

	exceptions	top
	assert
	ensure: Evaluate a termination block after evaluating the receiver, regardless of whether the receiver's evaluation completes.
	ifCurtailed: Evaluate the receiver with an abnormal termination action.
	on:do: Evaluate the receiver in the scope of an exception handler.

	initialize-release	top
	home:startpc:nargs: This is the initialization message. The receiver has been initialized with the correct size only.

	instruction decoding	top
	blockReturnTop Simulate the interpreter's action when a ReturnTopOfStack bytecode is encountered in the receiver.

	printing	top
	printOn: Append to the argument, aStream, a sequence of characters that identifies the receiver.
	printOnStream:

	private	top
	aboutToReturn:through: Use the passed in context as the first marked context; evaluate the unwind block and then scan upwards for the next unwind marked method context
	cannotReturn: The receiver tried to return result to a method context that no longer exists.
	instVarAt:put: Primitive. Store a value into a fixed variable in the receiver. The numbering of the variables corresponds to the named instance variables. Fail if the index is not an Integer or is not the index of a fixed variable. Answer the value stored as the result. Using this message violates the principle that each object has sovereign control over the storing of values into its instance variables. Essential. See Object documentation whatIsAPrimitive.
	startpc for use by the System Tracer only
	valueError
	valueUnpreemptively Evaluate the receiver (block), without the possibility of preemption by higher priority processes. Use this facility VERY sparingly!

	private-debugger	top
	hideFromDebugger

	private-exceptions	top
	ifProperUnwindSupportedElseSignalAboutToReturn A really ugly hack to simulate the necessary unwind behavior for VMs not having proper unwind support
	valueUninterruptably Temporarily make my home Context unable to return control to its sender, to guard against circumlocution of the ensured behavior.

	scheduling	top
	fork Create and schedule a Process running the code in the receiver.
	forkAt: Create and schedule a Process running the code in the receiver at the given priority. Answer the newly created process.
	newProcess Answer a Process running the code in the receiver. The process is not scheduled.
	newProcessWith: Answer a Process running the code in the receiver. The receiver's block arguments are bound to the contents of the argument, anArray. The process is not scheduled.

	system simulation	top
	pushArgs:from: Simulates action of the value primitive.
	stepToSendOrReturn Simulate the execution of bytecodes until either sending a message or returning a value to the receiver (that is, until switching contexts).

	tiles	top
	valueWithPossibleArgs: