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Verifier crashes on a for loop whose body is an empty statement (for (...) ;) #395
Description
Impact: verification stops with an internal error on any for loop whose body is an empty statement (;).
Description
for (...; ...; ...) ; has no body block: CtFor.getBody() is null, and RefinementTypeChecker.visitCtFor calls getElements on it (RefinementTypeChecker.java:628). Nothing in the loop needs a refinement, so an empty body could be checked as an empty block.
Minimal reproducer
public class Repro {
static int total(int[] counts) {
int total = 0;
for (int i = 0; i < counts.length; total += counts[i], i++)
;
return total;
}
}Expected
Correct! Passed Verification.
Actual
Exception in thread "main" java.lang.RuntimeException:
Error while checking CtMethodImpl
on total(int[] counts) {
at Repro.java:2
with
Error while checking CtBlockImpl
on {
at Repro.java:2
with
Error while checking CtForImpl
on for (int i = 0; i < counts.length; total += counts[i], i++)
at Repro.java:4
with Cannot invoke "spoon.reflect.code.CtStatement.getElements(spoon.reflect.visitor.Filter)" because the return value of "spoon.reflect.code.CtFor.getBody()" is null
...
Caused by: java.lang.NullPointerException: Cannot invoke "spoon.reflect.code.CtStatement.getElements(spoon.reflect.visitor.Filter)" because the return value of "spoon.reflect.code.CtFor.getBody()" is null
at liquidjava.processor.refinement_checker.RefinementTypeChecker.lambda$visitCtFor$4(RefinementTypeChecker.java:628)
at liquidjava.processor.refinement_checker.RefinementTypeChecker.visitLoop(RefinementTypeChecker.java:658)
at liquidjava.processor.refinement_checker.RefinementTypeChecker.visitCtFor(RefinementTypeChecker.java:623)
Reproduced on main at ad055b4 (liquidjava-verifier 0.0.35).
Real-world file that hits it
for (int i = 0; i < updateCount.length; cnt += updateCount[i], i++) ;— tejeswarp/tungsten-replicator (file)
Context
Found while running LiquidJava on the original repository files of 53 real-world typestate and refinement bugs (the files our study exercises were simplified from). Each file is verified on its own, as a user would verify one file of a project, so the project's other classes and its dependencies are not on the classpath.
Activity
Fix crashes on unresolved types and on empty for bodies (#432)