fix(memory_pool): add thread safety, overflow checks, and double-free protection

[0xfullex]

Summary

• Add pthread_mutex to protect all public functions for thread safety
• Add integer overflow check before chunk size multiplication to prevent memory corruption
• Add double-free detection using magic number at end of node
• Align node_size to max_align_t for proper memory alignment
• Fix format string argument order in memory_pool_check_node()
• Add NULL pointer check in memory_pool_free()

Changes

Thread Safety

• Added pthread_mutex_t mutex to MEMORY_POOL struct
• Initialize mutex in memory_pool_init(), destroy in memory_pool_cleanup()
• Lock/unlock mutex in memory_pool_alloc() and memory_pool_free()

Integer Overflow Protection

• Check node_count_per_chunk > SIZE_MAX / node_size before multiplication in memory_pool_add_chunk()

Double-Free Detection

• Added magic number constants MEMORY_POOL_MAGIC_ALLOCATED and MEMORY_POOL_MAGIC_FREE
• Check and set magic number in memory_pool_free() to detect double-free attempts

Memory Alignment

• Added align_size() helper function to align node_size to max_align_t

Bug Fixes

• Fixed format string argument order in memory_pool_check_node() log message
• Added NULL check for p_node parameter in memory_pool_free()

Test Plan

• Compile verification passed
• Manual testing with existing application
• Concurrent access testing

🤖 Generated with Claude Code

[leafok88]

This memory pool is used in multi-process application. Therefore, pthread_mutex is not a proper solution for concurrency control.