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False error: a local declared inside try is "not found" at a call in finally

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#406 0 comentarios 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
20/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
java
Área
compilers

Línea de trabajo

Start by reproducing the report: save the Repro class from the issue and run LiquidJava on it to see the Not Found Error at input.close() in the finally. The cause is that the state of input recorded at the end of the try still mentions the block-local length, which is out of scope when the finally checks close(). Done means the repro passes verification and the change does not break the existing tests.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

bug

With the Barista BufferedInputStream spec (read() returns _ >= -1; read(byte[], int, int) refines its length):

import java.io.*;

public class Repro {
    static int load(InputStream raw, boolean known) throws IOException {
        BufferedInputStream input = new BufferedInputStream(raw);
        try {
            int cost = 0;
            if (known) {
                int length = input.read();
                if (length >= 0) {
                    byte[] nonce = new byte[length];
                    input.read(nonce, 0, length);
                }
            }
            return cost;
        } finally {
            input.close();
        }
    }
}

On main 1c6807be (and 321a7321):

Not Found Error: Variable 'length' could not be found
  input.close();   (in the finally)

length is a block-local of the try; the state of input recorded in the try (after read(nonce, 0, length)) mentions it, and when the finally checks close() against that state, length is out of scope. Expected: Correct! Passed Verification. (out-of-scope locals should be eliminated or kept as fresh variables when the state flows into the finally / after the block).

Found in a real-code example (secrets-for-android FileUtils, a length-prefixed read in try/finally). Since #366 the example's earlier workaround (guarding with a block instead of an early return) no longer avoids it.

Lenguaje dominante
Java
Estrellas
69
Forks
36
Merge medio
2 d 1 h
PR fusionados (30 d)
35

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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