c++ - Array size at run time without dynamic allocation is allowed? -

i've been using c++ few years, , today saw code, how can legal?

int main(int argc, char **argv) {     size_t size;     cin >> size;     int array[size];     for(size_t = 0; < size; i++)     {         array[i] = i;         cout << << endl;     }      return 0; } 

^{compiled under gcc.}

how can size determined @ run-time without new or malloc?

just double check, i've googled , similar codes mine claimed give storage size error.

even deitel's c++ how program p. 261 states under common programming error 4.5:

only constants can used declare size of automatic , static arrays.

enlight me.

this valid in c99.

c99 standard supports variable sized arrays on stack. compiler has chosen support construct too.

note different malloc , new. gcc allocates array on stack, int array[100] adjusting stack pointer. no heap allocation done. it's pretty _alloca.