C String & Buffer Safety

When to use

• Writing C that copies user-controlled or variable-length strings into fixed buffers.
• Reviewing code that uses strncpy, snprintf, strcpy, strcat, sprintf, gets, memcpy, memset.
• Checking whether a buffer is large enough for what is copied into it.
• Reasoning about truncation: does the call report when the output was cut off?
• Porting code between BSD (strlcpy/strscpy), Linux kernel, and standard C11 environments.

When not to use

• Pure C++ code with std::string / std::vector — see raii-descriptor-types-api-design.
• Rust — ownership + bounds checks are compile-time; use rust-unsafe-reasoning for unsafe blocks.
• When the concern is a specific UB construct rather than string copying, route through c-undefined-behavior.
• Memory allocation correctness (leaks, double-free) — that is memory ownership, not buffer sizing.

What the agent often gets wrong