modbender Quick Reference
| Topic | File |
|---|---|
| malloc/free, leaks, double free | memory.md |
| Null, dangling, pointer arithmetic | pointers.md |
| Null terminator, buffer overflow | strings.md |
| Integer overflow, signed/unsigned | types.md |
| Macro traps, include guards | preprocessor.md |
| Common undefined behavior | undefined.md |
Critical Rules
mallocreturnsvoid*— cast required in C++, optional in C but check for NULLfree(ptr); ptr = NULL;— always null after free to prevent double-freesizeof(array)in function gives pointer size, not array size — pass length separatelychar str[5] = "hello";— no room for null terminator, UB when used as stringstrcpydoesn't check bounds — usestrncpyand manually null-terminate- Signed overflow is UB — compiler can optimize assuming it never happens
i++ + i++is UB — no sequence point between modifications- Returning pointer to local variable — dangling pointer, UB on use
#define SQUARE(x) x*x—SQUARE(1+2)=1+2*1+2= 5, not 9memcpywith overlapping regions — usememmoveinstead- Uninitialized variables — contain garbage, UB if used
- Array out of bounds — no runtime check, silent corruption or crash