c - Why this line make my program segfault? -

i cut useless part of code make post clearer.

here problem, first , line in function init_dda() make programme segfault, don't understand how possible, if have explanation, you.

void    dda_algorithm(t_env *e) {     t_dda   *d;      d = null;     init_dda(e, d); }  void    init_dda(t_env *e, t_dda *d) {     d->map_x = 3; } 

here construction of structure t_dda:

typedef struct  s_dda {     int         map_x; }               t_dda; 

i have no compilation error warning flags enabled.

in init_dda() call, you're passing second argument d null.

then, inside init_dda(), you're trying de-reference pointer. (dereferencing null pointer, invalid pointer) invokes undefined behaviour. segmentation fault 1 of side effects.

solution: need allocate memory d before passing init_dda(). can malloc() , family of functions.