Question

I developed a mechanism for function callback. This is my function.

int function_root(var1,var2, int(*callback)(), ...);

so if var1=var2 then callback(va_arg list);

For example:

function_root(a,b,fun_clbck,x,y,z); //if a=b
we will get this: fun_clbk(x, y, z);

Problem is. When my function callback have at least one argument. I get a warning incompatibility with prototype

I think the problem is in my function root. I declared int(*callback)() with zero parameter and once I do a callback like fun_clbck(int,int,int); it triggers that problem.

Answer 1

i declared int(*callback)() with zero parameter

That’s not true. int(*callback)() is not a C89/C99 prototype; it declares a function pointer to something returning int, without specifying types of parameters. The proper declaration for a function pointer with no arguments would be

int (*callback)(void)

and once i do a callback like fun_clbck(int,int,int); it trigger that problem

Obviously. The parameter types declared for the callback function must match that in the call. Rethink your design, e.g. use a variable number of arguments:

int (*callback)(unsigned, ...)

and pass the number of actual arguments as the first parameter.