Question

Is it possible to assign with cast to a function pointer a string or char array and then run it?

I have defined a few functions int f1();, int f2();, and so on

In the main() function I have read a string fct_name and declared a pointer to function int (*pv)();

I need to do something like this:

the fct_name can have values “f1” , “f2” and so on..

pv = (some sort of cast)fct_name;

pv();

My point is I want to avoid conditional instructions in favor of direct assignment (because I have a large number of functions in my program)

The code must obviously run.

Answer 1

Assuming you don’t have an external library and are trying to call functions declared in your executable, you can do a lookup yourself

#define REGISTER_FUNC(name)  {#name, name}

struct funclist
{
    const char* name;
    void (*fp)(void);  //or some other signature
};

struct funclist AllFuncs[] = {
    REGISTER_FUNC(f1),
    REGISTER_FUNC(f2),
    REGISTER_FUNC(f3),
    {NULL,NULL}  //LAST ITEM SENTINEL
 };

Now you can lookup your variable fct_name in AllFuncs. You can use a linear search if the number is small, or insert them all into a hash table for O(1) lookup.

Alternately, if your names really are f1, f2, etc. you can just do

   void (*FuncList)(void)[]  = {NULL, f1,f2,f3};
   ...
   int idx = atol(fct_name+1);
   if (idx && idx < MAX_FUNCS)  
       FuncList[idx]();