4 ms·

Code that does things like strcat(strcat(strcat(strcpy(...), ...), ...), ...)

• jonathrg 4y ago
  If I understand the implementation section of the proposal correctly, the preprocessor will just add ome cast to (const char*) per function call (assuming the innermost argument is const). Nothing exponential
  • lifthrasiir 4y ago
    For the ease of discussion here is the relevant piece of code: #define IS_POINTER_CONST(P) _Generic(1 ? (P) : (void *)(P) \ , void const *: 1 \ , default : 0) #define STATIC_IF(P, T, E) _Generic (&(char [!!(P) + 1]) {0} \ , char (*) [2] : T \ , char (*) [1] : E) #define _STRING_SEARCH_QP(T, F, S, ...) \ STATIC_IF (IS_POINTER_CONST ((S)) \ , (T const *) (F) ((S), __VA_ARGS__) \ , (T *) (F) ((S), __VA_ARGS__)) #define memchr(S, C, N) _STRING_SEARCH_QP(void, memchr, (S), (C), (N)) #define strchr(S, C) _STRING_SEARCH_QP(char, strchr, (S), (C)) #define strpbrk(S1, S2) _STRING_SEARCH_QP(char, strpbrk, (S1), (S2)) #define strrchr(S, C) _STRING_SEARCH_QP(char, strrchr, (S), (C)) #define strstr(S1, S2) _STRING_SEARCH_QP(char, strstr, (S1), (S2)) Here `IS_POINTER_COST` expands `P` twice so `_STRING_SEARCH_QP` expands `T`, `F`, `S` and each variadic argument 2, 2, 4 and 2 times respectively. Note that only `S` and variadic arguments are expressions and evaluated only once, but the number of expanded tokens can blow up exponentially.