/**
* Whenever the outgoing frame situation of an InstructionContext changes, all its successors are
* put [back] into the queue [as if they were unvisited]. The proof of termination is about the
* existence of a fix point of frame merging.
*/
private void circulationPump(
ControlFlowGraph cfg,
InstructionContext start,
Frame vanillaFrame,
InstConstraintVisitor icv,
ExecutionVisitor ev) {
final Random random = new Random();
InstructionContextQueue icq = new InstructionContextQueue();
start.execute(
vanillaFrame,
new ArrayList(),
icv,
ev); // new ArrayList() <=> no Instruction was executed before
// => Top-Level routine (no jsr call before)
icq.add(start, new ArrayList());
// LOOP!
while (!icq.isEmpty()) {
InstructionContext u;
ArrayList ec;
if (!DEBUG) {
int r = random.nextInt(icq.size());
u = icq.getIC(r);
ec = icq.getEC(r);
icq.remove(r);
} else {
u = icq.getIC(0);
ec = icq.getEC(0);
icq.remove(0);
}
ArrayList oldchain = (ArrayList) (ec.clone());
ArrayList newchain = (ArrayList) (ec.clone());
newchain.add(u);
if ((u.getInstruction().getInstruction()) instanceof RET) {
// System.err.println(u);
// We can only follow _one_ successor, the one after the
// JSR that was recently executed.
RET ret = (RET) (u.getInstruction().getInstruction());
ReturnaddressType t =
(ReturnaddressType) u.getOutFrame(oldchain).getLocals().get(ret.getIndex());
InstructionContext theSuccessor = cfg.contextOf(t.getTarget());
// Sanity check
InstructionContext lastJSR = null;
int skip_jsr = 0;
for (int ss = oldchain.size() - 1; ss >= 0; ss--) {
if (skip_jsr < 0) {
throw new AssertionViolatedException("More RET than JSR in execution chain?!");
}
// System.err.println("+"+oldchain.get(ss));
if (((InstructionContext) oldchain.get(ss)).getInstruction().getInstruction()
instanceof JsrInstruction) {
if (skip_jsr == 0) {
lastJSR = (InstructionContext) oldchain.get(ss);
break;
} else {
skip_jsr--;
}
}
if (((InstructionContext) oldchain.get(ss)).getInstruction().getInstruction()
instanceof RET) {
skip_jsr++;
}
}
if (lastJSR == null) {
throw new AssertionViolatedException(
"RET without a JSR before in ExecutionChain?! EC: '" + oldchain + "'.");
}
JsrInstruction jsr = (JsrInstruction) (lastJSR.getInstruction().getInstruction());
if (theSuccessor != (cfg.contextOf(jsr.physicalSuccessor()))) {
throw new AssertionViolatedException(
"RET '"
+ u.getInstruction()
+ "' info inconsistent: jump back to '"
+ theSuccessor
+ "' or '"
+ cfg.contextOf(jsr.physicalSuccessor())
+ "'?");
}
if (theSuccessor.execute(u.getOutFrame(oldchain), newchain, icv, ev)) {
icq.add(theSuccessor, (ArrayList) newchain.clone());
}
} else { // "not a ret"
// Normal successors. Add them to the queue of successors.
InstructionContext[] succs = u.getSuccessors();
for (int s = 0; s < succs.length; s++) {
InstructionContext v = succs[s];
if (v.execute(u.getOutFrame(oldchain), newchain, icv, ev)) {
icq.add(v, (ArrayList) newchain.clone());
}
}
} // end "not a ret"
// Exception Handlers. Add them to the queue of successors.
// [subroutines are never protected; mandated by JustIce]
ExceptionHandler[] exc_hds = u.getExceptionHandlers();
for (int s = 0; s < exc_hds.length; s++) {
InstructionContext v = cfg.contextOf(exc_hds[s].getHandlerStart());
// TODO: the "oldchain" and "newchain" is used to determine the subroutine
// we're in (by searching for the last JSR) by the InstructionContext
// implementation. Therefore, we should not use this chain mechanism
// when dealing with exception handlers.
// Example: a JSR with an exception handler as its successor does not
// mean we're in a subroutine if we go to the exception handler.
// We should address this problem later; by now we simply "cut" the chain
// by using an empty chain for the exception handlers.
// if (v.execute(new Frame(u.getOutFrame(oldchain).getLocals(), new OperandStack
// (u.getOutFrame().getStack().maxStack(), (exc_hds[s].getExceptionType()==null?
// Type.THROWABLE : exc_hds[s].getExceptionType())) ), newchain), icv, ev){
// icq.add(v, (ArrayList) newchain.clone());
if (v.execute(
new Frame(
u.getOutFrame(oldchain).getLocals(),
new OperandStack(
u.getOutFrame(oldchain).getStack().maxStack(),
(exc_hds[s].getExceptionType() == null
? Type.THROWABLE
: exc_hds[s].getExceptionType()))),
new ArrayList(),
icv,
ev)) {
icq.add(v, new ArrayList());
}
}
} // while (!icq.isEmpty()) END
InstructionHandle ih = start.getInstruction();
do {
if ((ih.getInstruction() instanceof ReturnInstruction) && (!(cfg.isDead(ih)))) {
InstructionContext ic = cfg.contextOf(ih);
Frame f =
ic.getOutFrame(
new ArrayList()); // TODO: This is buggy, we check only the top-level return
// instructions this way. Maybe some maniac returns from a method
// when in a subroutine?
LocalVariables lvs = f.getLocals();
for (int i = 0; i < lvs.maxLocals(); i++) {
if (lvs.get(i) instanceof UninitializedObjectType) {
this.addMessage(
"Warning: ReturnInstruction '"
+ ic
+ "' may leave method with an uninitialized object in the local variables array '"
+ lvs
+ "'.");
}
}
OperandStack os = f.getStack();
for (int i = 0; i < os.size(); i++) {
if (os.peek(i) instanceof UninitializedObjectType) {
this.addMessage(
"Warning: ReturnInstruction '"
+ ic
+ "' may leave method with an uninitialized object on the operand stack '"
+ os
+ "'.");
}
}
}
} while ((ih = ih.getNext()) != null);
}
