When a free/cleanup API may receive NULL (or an invalid handle), don’t rely on ad-hoc checks at call sites. Instead, define a NULL-safe wrapper/helper that: - No-ops when the argument is NULL (mirrors `free(NULL)` semantics). - Avoids double-evaluation (store the argument in a temporary). - Preserves compile-time type checking (use a correctly typed temporary; avoid unnecessary casts). - Is safe to use across versions when needed (e.g., macro wrapper vs direct symbol). - Also guard cleanup operations (e.g., `close`) to run only when the handle was actually acquired. Example pattern (C): ```c /* NULL-safe wrapper: evaluates arg once, type-checked, no-op on NULL */ #define Module_FreeStringSafe(ctx, str) \ do { \ RedisModuleString *_ms = (str); \ if (_ms) RedisModule_FreeString(ctx, _ms); \ } while (0) ``` Example guard (Tcl): ```tcl if {$fd ne {}} { catch {close $fd} } ``` Apply this rule consistently to any code path that frees/finalizes memory or resources that might be absent due to conditional logic or partial failures.