/**
* Returns the subroutine object associated with the given instruction. This is a costly
* operation, you should consider using getSubroutine(InstructionHandle). Returns 'null' if the
* given InstructionHandle lies in so-called 'dead code', i.e. code that can never be executed.
*
* @see #getSubroutine(InstructionHandle)
* @see #getTopLevel()
*/
public Subroutine subroutineOf(InstructionHandle any) {
Iterator i = subroutines.values().iterator();
while (i.hasNext()) {
Subroutine s = (Subroutine) i.next();
if (s.contains(any)) return s;
}
System.err.println("DEBUG: Please verify '" + any + "' lies in dead code.");
return null;
// throw new AssertionViolatedException("No subroutine for InstructionHandle found (DEAD
// CODE?).");
}
/**
* This (recursive) utility method makes sure that no subroutine is calling a subroutine that uses
* the same local variable for the RET as themselves (recursively). This includes that subroutines
* may not call themselves recursively, even not through intermediate calls to other subroutines.
*
* @throws StructuralCodeConstraintException if the above constraint is not satisfied.
*/
private void noRecursiveCalls(Subroutine sub, HashSet<Integer> set) {
Subroutine[] subs = sub.subSubs();
for (int i = 0; i < subs.length; i++) {
int index = ((RET) (subs[i].getLeavingRET().getInstruction())).getIndex();
if (!set.add(new Integer(index))) {
// Don't use toString() here because of possibly infinite recursive subSubs() calls then.
SubroutineImpl si = (SubroutineImpl) subs[i];
throw new StructuralCodeConstraintException(
"Subroutine with local variable '"
+ si.localVariable
+ "', JSRs '"
+ si.theJSRs
+ "', RET '"
+ si.theRET
+ "' is called by a subroutine which uses the same local variable index as itself; maybe even a recursive call? JustIce's clean definition of a subroutine forbids both.");
}
noRecursiveCalls(subs[i], set);
set.remove(new Integer(index));
}
}
/**
* Constructor.
*
* @param il A MethodGen object representing method to create the Subroutine objects of.
*/
public Subroutines(MethodGen mg) {
InstructionHandle[] all = mg.getInstructionList().getInstructionHandles();
CodeExceptionGen[] handlers = mg.getExceptionHandlers();
// Define our "Toplevel" fake subroutine.
TOPLEVEL = new SubroutineImpl();
// Calculate "real" subroutines.
HashSet<InstructionHandle> sub_leaders =
new HashSet<InstructionHandle>(); // Elements: InstructionHandle
for (int i = 0; i < all.length; i++) {
Instruction inst = all[i].getInstruction();
if (inst instanceof JsrInstruction) {
sub_leaders.add(((JsrInstruction) inst).getTarget());
}
}
// Build up the database.
Iterator iter = sub_leaders.iterator();
while (iter.hasNext()) {
SubroutineImpl sr = new SubroutineImpl();
InstructionHandle astore = (InstructionHandle) (iter.next());
sr.setLocalVariable(((ASTORE) (astore.getInstruction())).getIndex());
subroutines.put(astore, sr);
}
// Fake it a bit. We want a virtual "TopLevel" subroutine.
subroutines.put(all[0], TOPLEVEL);
sub_leaders.add(all[0]);
// Tell the subroutines about their JsrInstructions.
// Note that there cannot be a JSR targeting the top-level
// since "Jsr 0" is disallowed in Pass 3a.
// Instructions shared by a subroutine and the toplevel are
// disallowed and checked below, after the BFS.
for (int i = 0; i < all.length; i++) {
Instruction inst = all[i].getInstruction();
if (inst instanceof JsrInstruction) {
InstructionHandle leader = ((JsrInstruction) inst).getTarget();
((SubroutineImpl) getSubroutine(leader)).addEnteringJsrInstruction(all[i]);
}
}
// Now do a BFS from every subroutine leader to find all the
// instructions that belong to a subroutine.
HashSet<InstructionHandle> instructions_assigned =
new HashSet<InstructionHandle>(); // we don't want to assign an instruction to two or more
// Subroutine objects.
Hashtable<InstructionHandle, Color> colors =
new Hashtable<
InstructionHandle,
Color>(); // Graph colouring. Key: InstructionHandle, Value: java.awt.Color .
iter = sub_leaders.iterator();
while (iter.hasNext()) {
// Do some BFS with "actual" as the root of the graph.
InstructionHandle actual = (InstructionHandle) (iter.next());
// Init colors
for (int i = 0; i < all.length; i++) {
colors.put(all[i], Color.white);
}
colors.put(actual, Color.gray);
// Init Queue
ArrayList<InstructionHandle> Q = new ArrayList<InstructionHandle>();
Q.add(actual); // add(Obj) adds to the end, remove(0) removes from the start.
/* BFS ALGORITHM MODIFICATION: Start out with multiple "root" nodes, as exception handlers are starting points of top-level code, too. [why top-level? TODO: Refer to the special JustIce notion of subroutines.]*/
if (actual == all[0]) {
for (int j = 0; j < handlers.length; j++) {
colors.put(handlers[j].getHandlerPC(), Color.gray);
Q.add(handlers[j].getHandlerPC());
}
}
/* CONTINUE NORMAL BFS ALGORITHM */
// Loop until Queue is empty
while (Q.size() != 0) {
InstructionHandle u = (InstructionHandle) Q.remove(0);
InstructionHandle[] successors = getSuccessors(u);
for (int i = 0; i < successors.length; i++) {
if (((Color) colors.get(successors[i])) == Color.white) {
colors.put(successors[i], Color.gray);
Q.add(successors[i]);
}
}
colors.put(u, Color.black);
}
// BFS ended above.
for (int i = 0; i < all.length; i++) {
if (colors.get(all[i]) == Color.black) {
((SubroutineImpl) (actual == all[0] ? getTopLevel() : getSubroutine(actual)))
.addInstruction(all[i]);
if (instructions_assigned.contains(all[i])) {
throw new StructuralCodeConstraintException(
"Instruction '"
+ all[i]
+ "' is part of more than one subroutine (or of the top level and a subroutine).");
} else {
instructions_assigned.add(all[i]);
}
}
}
if (actual != all[0]) { // If we don't deal with the top-level 'subroutine'
((SubroutineImpl) getSubroutine(actual)).setLeavingRET();
}
}
// Now make sure no instruction of a Subroutine is protected by exception handling code
// as is mandated by JustIces notion of subroutines.
for (int i = 0; i < handlers.length; i++) {
InstructionHandle _protected = handlers[i].getStartPC();
while (_protected
!= handlers[i]
.getEndPC()
.getNext()) { // Note the inclusive/inclusive notation of "generic API" exception
// handlers!
Enumeration subs = subroutines.elements();
while (subs.hasMoreElements()) {
Subroutine sub = (Subroutine) subs.nextElement();
if (sub
!= subroutines.get(all[0])) { // We don't want to forbid top-level exception handlers.
if (sub.contains(_protected)) {
throw new StructuralCodeConstraintException(
"Subroutine instruction '"
+ _protected
+ "' is protected by an exception handler, '"
+ handlers[i]
+ "'. This is forbidden by the JustIce verifier due to its clear definition of subroutines.");
}
}
}
_protected = _protected.getNext();
}
}
// Now make sure no subroutine is calling a subroutine
// that uses the same local variable for the RET as themselves
// (recursively).
// This includes that subroutines may not call themselves
// recursively, even not through intermediate calls to other
// subroutines.
noRecursiveCalls(getTopLevel(), new HashSet<Integer>());
}