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Verifier crashes on a `for` loop whose body is an empty statement (`for (...) ;`)

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1-3 小时
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82/100
Issue 类型
缺陷
描述清晰度
描述清楚
活跃度
活跃
技术栈
java
领域
tooling

调研方向

崩溃位于 src/main/java/liquidjava/processor/refinement_checker/RefinementTypeChecker.java 中的 visitCtFor,其中一个 lambda 在大约第 628 行对 CtFor.getBody() 调用了 getElements;同一路径在大约第 658 行经过 visitLoop。先阅读那里如何消费循环体,然后运行 issue 中的复现示例,它的循环体为空 ;。当该复现示例输出 Correct! Passed Verification.,并且现有的循环测试仍然通过时,即完成。

由索引模型根据 Issue 内容生成。

描述

bug

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 ad055b49 (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.

主要语言
Java
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