Add null checks to fix SEGV

[k-raina]

Overview

This PR fixes segmentation fault (SEGV) issues that occur when Kafka client methods are called on uninitialized instances. The fix addresses issue #1590

Problem

When a class is derived from Producer, Consumer, or AdminClient and doesn't call super().__init__(), the internal self->rk pointer in the C code remains NULL. Calling methods on such instances causes segmentation faults because these methods attempt to use self->rk without checking if it's NULL.

Example Crash Scenario

class MyProducer(Producer):
    def __init__(self, config):
        # Missing: super().__init__(config)
        # This leaves self->rk as NULL in the C code
        pass

producer = MyProducer({'bootstrap.servers': 'localhost:9092'})
producer.flush()  # CRASH: rd_kafka_flush(NULL, ...) → SEGV

Solution

Null Checks Added

Added null checks before operations in all affected methods using a consistent pattern:

if (!self->rk) {
    PyErr_SetString(PyExc_RuntimeError, ERR_MSG_*_CLOSED);
    return NULL;  // or goto err; for methods with cleanup
}

The checks are placed:

• After argument parsing (to avoid unnecessary work)
• Before any use of self->rk (to prevent NULL dereference)

Changes

Producer (src/confluent_kafka/src/Producer.c)

Added null checks to 7 methods that were missing them:

• Producer_produce_batch() - Added check before rd_kafka_topic_new()
• Producer_init_transactions() - Added check before rd_kafka_init_transactions()
• Producer_begin_transaction() - Added check before rd_kafka_begin_transaction()
• Producer_send_offsets_to_transaction() - Added check with proper cleanup of cgmd and c_offsets
• Producer_commit_transaction() - Added check before rd_kafka_commit_transaction()
• Producer_abort_transaction() - Added check before rd_kafka_abort_transaction()
• Producer_purge() - Added check before rd_kafka_purge()

Consumer (src/confluent_kafka/src/Consumer.c)

Added null checks to all Consumer methods that were missing them:

• Consumer_commit()
• Consumer_committed()
• Consumer_position()
• Consumer_seek()
• Consumer_get_watermark_offsets()
• Consumer_store_offsets()
• Consumer_offsets_for_times()
• Consumer_consumer_group_metadata()
• And other methods

AdminClient (src/confluent_kafka/src/Admin.c)

Added null checks to all AdminClient methods:

• Admin_create_topics()
• Admin_delete_topics()
• Admin_create_partitions()
• Admin_describe_configs()
• Admin_alter_configs()
• Admin_incremental_alter_configs()
• Admin_create_acls()
• Admin_delete_acls()
• Admin_describe_acls()
• Admin_list_consumer_groups()
• Admin_describe_consumer_groups()
• And all other Admin API methods

Test Coverage

Producer Tests (tests/test_Producer.py)

Consumer Tests (tests/test_Consumer.py)

AdminClient Tests (tests/test_Admin.py)

All tests verify that:

1. Methods raise RuntimeError instead of crashing
2. Error messages are consistent and descriptive
3. No segmentation faults occur

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[Copilot]

Pull Request Overview

This PR adds null checks to prevent segmentation faults when Kafka client methods are called on uninitialized instances (where super().__init__() was not called). The fix addresses issue #1590 by checking if the internal self->rk handle is NULL before operations and raising appropriate RuntimeError exceptions.

Key changes:

• Added standardized error message constants for closed/uninitialized client states
• Added NULL checks before operations in Producer, Consumer, and AdminClient methods
• Added comprehensive test coverage for all affected methods

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/confluent_kafka/src/confluent_kafka.h	Defines error message constants for uninitialized/closed client states
src/confluent_kafka/src/Producer.c	Adds NULL checks to Producer methods and uses standardized error messages
src/confluent_kafka/src/Consumer.c	Adds NULL checks to Consumer methods and uses standardized error messages
src/confluent_kafka/src/Admin.c	Adds NULL checks to AdminClient methods and uses standardized error messages
src/confluent_kafka/src/Metadata.c	Updates metadata methods to use standardized error message constants
tests/test_Producer.py	Adds test coverage for uninitialized Producer instance behavior
tests/test_Consumer.py	Adds test coverage for uninitialized Consumer instance behavior
tests/test_Admin.py	Adds test coverage for uninitialized AdminClient instance behavior

---

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[Copilot]

The cleanup of cgmd and c_offsets before the NULL check creates resource management complexity. Consider moving the NULL check before argument parsing to avoid unnecessary resource allocation and cleanup when the producer is uninitialized.

[Copilot]

Extra blank line should be removed to maintain consistent spacing with other test functions.

Suggested change

[sonarqube-confluent]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube