nginx.org C Module Debugging Best Practices

Comprehensive debugging guide for nginx C modules, derived from the official nginx development documentation and production debugging experience. Contains 45 rules across 8 categories, prioritized by impact to guide systematic diagnosis of crashes, memory bugs, and behavioral issues in nginx modules.

Companion skills: This skill complements nginx-c-module-best-practices (correctness) and nginx-c-module-perf-reliability (performance). This skill covers debugging and diagnosis.

When to Apply

Reference these guidelines when:

• Diagnosing nginx worker crashes (segfaults, SIGABRT, SIGSEGV)
• Finding memory bugs (use-after-free, leaks, pool corruption, buffer overruns)
• Setting up GDB and core dump analysis for nginx
• Tracing request flow through phases, subrequests, and filter chains
• Instrumenting nginx modules with debug logging and dynamic tracing tools

Rule Categories by Priority