c - Using right pointer type, dont want to cast with void * -

question regarding using correct pointer type in below code. when try initialize struct member function without type casting void *, got “initialization incompatible pointer type” warnings ?

problem solved typecasting want use right pointer type instead of casting void*.

code snippet:

#include <stdio.h> #include <string.h> #include <stdlib.h>   typedef void (*set_id)(int id); typedef void (*set_name)(char *name);  typedef struct prop {     set_id *cb_setting_id;     set_name *cb_setting_name; }prop;   prop *setting_id(int id) {     printf("id:%d\n", id);   }  prop *setting_name(char *in) {     char *name;     name = in;     printf("name:%s\n", name); } //here type casted void *, if not wrong pointer initalization  //error prop cb_prop = { .cb_setting_id=(void *)setting_id,                       .cb_setting_name=(void *)setting_name };  int main() {      prop *cb_event;      cb_event = &cb_prop;      cb_event->cb_setting_id = (void*)setting_id(2);     cb_event->cb_setting_name = (void*)setting_name("/dev/ttys1");      return 0;    } 

without type casting, warning are:

struct_callback.c:25:33: warning: initialization incompatible pointer type [-wincompatible-pointer-types]      prop cb_prop = { .cb_setting_id=setting_id,                                      ^ struct_callback.c:25:33: note: (near initialization ‘cb_prop.cb_setting_id’) struct_callback.c:32:26: warning: assignment incompatible pointer type [-wincompatible-pointer-types]   cb_event->cb_setting_id = setting_id(2); 

check definition of e.g. set_id type alias, pointer function taking int argument , not returning anything. compare setting_id function, function takes int arguments , returns pointer prop. 2 types not compatible. it's made worse because setting_id function declared return pointer prop doesn't return anything.

and not that, members in structure pointers e.g. set_id means cb_setting_id pointer pointer function.

later on do

cb_event->cb_setting_id = (void*)setting_id(2); 

this wrong because calls setting_id function, , tries assign returned value cb_event->cb_setting_id. setting_id function doesn't return anything.

the solution first problem make sure both set_id type , function setting_id equal.

the solution second problem not declare members pointers (since are), or changing set_id not pointer.

the solution third problem remove lines, since the first 2 solutions should solve initial initialization of cb_prop structure.