c-standards

name	c-standards
description	C coding standards with severity-tiered rules. Use when writing, reviewing, or generating C code.

C Standards

ERROR (mandatory)

• Check all return values from system calls and memory allocations
• No buffer overflows — validate all array indices and string operations
• Use snprintf over sprintf, strncpy over strcpy
• Free all dynamically allocated memory — no leaks
• No undefined behavior: no signed integer overflow, null pointer dereference, or use-after-free
• Initialize all variables before use
• No gets() — ever

WARNING (recommended)

• Use const for parameters and variables that don't change
• Prefer static for file-scoped functions and variables
• Use sizeof(variable) not sizeof(type) for allocations
• Maximum function length: 60 lines (excluding declarations)
• Use enum for related constants — avoid magic numbers
• Use static_assert (C11) for compile-time invariants
• Prefer stdint.h types (uint32_t) over platform-dependent types

RECOMMENDATION (optional)

• Use compound literals for struct initialization
• Consider _Generic for type-safe macros (C11)
• Use restrict qualifier for non-aliasing pointer parameters
• Structure packing: align members to minimize padding
• Use __attribute__((cleanup)) or RAII-like patterns for resource management

Memory Safety Checklist

• Every malloc/calloc/realloc has a corresponding free
• Pointers set to NULL after free
• Array bounds checked before access
• String buffers sized for content + null terminator
• No stack-allocated large arrays (>4KB on stack)

Testing

• Test boundary conditions: empty, max, off-by-one
• Memory leak detection: Valgrind, AddressSanitizer
• Undefined behavior: -fsanitize=undefined
• Fuzz testing for input parsing functions