René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"coredump in `TryCopyLastError`","articleBody":"### Describe the bug, including details regarding any error messages, version, and platform.\n\nIf `Consumer` throws exception, `TryCopyLastError` would copy exception message to C buffer. `TryCopyLastError` assume the string(byte[]) returned by `lastError` is '\\0' terminated and test the length of the string by `strlen` which result in invalid memory access. In actually, `lastError` is a UTF8 encoded buffer(byte[]).\n\nThe code of `TryCopyLastError`:\n\n```c\n  jobject error_data =\n      env-\u003eGetObjectField(private_data-\u003ej_private_data_, kPrivateDataLastErrorField);\n  ...\n  auto arr = reinterpret_cast\u003cjbyteArray\u003e(error_data);\n  jbyte* error_bytes = env-\u003eGetByteArrayElements(arr, nullptr);\n  if (!error_bytes) {\n    private_data-\u003elast_error_.clear();\n    return;\n  }\n\n  char* error_str = reinterpret_cast\u003cchar*\u003e(error_bytes);\n  private_data-\u003elast_error_ = std::string(error_str, std::strlen(error_str));\n```\n\nThe code below shows how `lastError` be setted:\n```java\nprivate int setLastError(Throwable err) {\n      // Do not let exceptions propagate up to JNI\n      try {\n        StringWriter buf = new StringWriter();\n        PrintWriter writer = new PrintWriter(buf);\n        err.printStackTrace(writer);\n        lastError = buf.toString().getBytes(StandardCharsets.UTF_8);\n      } catch (Throwable e) {\n        // Bail out of setting the error message - we'll still return an error code\n        lastError = null;\n      }\n      return 5; // = EIO\n    }\n```","author":{"url":"https://github.com/hnwyllmm","@type":"Person","name":"hnwyllmm"},"datePublished":"2025-05-20T03:57:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/759/arrow-java/issues/759"}