Returning function pointer type

Question

Often I find the need to write functions which return function pointers. Whenever I do, the basic format I use is:

typedef int (*function_type)(int,int);

fu         


        

Answer 1

int (*getFunc())(int, int) { … }

That provides the declaration you requested. Additionally, as ola1olsson notes, it would be good to insert void:

int (*getFunc(void))(int, int) { … }

This says that getFunc may not take any parameters, which can help avoid errors such as somebody inadvertently writing getFunc(x, y) instead of getFunc()(x, y).

Answer 2

You can write the following code(It only works in C++11 and above):

//C++11
auto func(...) {
    int (*fptr)(...) ret = ...
    //Do sth.
    return ret;//C++11 compiler will automatically deduce the return type for you
}

Or, if you do not like automatic return type deduction, you can specified the type at the end of the function(Same as above, only in C++11 and above):

//C++11
auto func(...) -> int (*)(...) { /* Do sth. */ }

Answer 3

You can probably do something like:

int foo (char i) {return i*2;}

int (*return_foo()) (char c)
{
   return foo;
}

but god, I hope I'll never have to debug you code....

Answer 4

I think you've got three options:

1. Stick with typedef. At the end of the day, it's typedef's job.
2. Return void* and the casting it.
3. Reconsider your software architecture. Perhaps you could share with us what you're trying to achieve and see if we can point you toward a better direction.

Answer 5

This is a stupid example, but it's simple and it does not give errors. It's just about declaring static functions:

#include <stdio.h>
#include <stdlib.h>

void * asdf(int);
static int * hjkl(char,float);

main() {
  int a = 0;
  asdf(a);
 }


void * asdf(int a) {return (void *)hjkl; }
static int * hjkl(char a, float b) {int * c; return c;}

Answer 6

ill leave this here since it was a bit trickier than answers already given, as it takes a function pointer

(int (__cdecl *)(const char *))

and returns a function pointer

(int (__cdecl *)(const char *))

#include <stdio.h>

int (*idputs(int (*puts)(const char *)))(const char *) {
    return puts;
}

int main(int argc, char **argv)
{
    idputs(puts)("Hey!");

    return 0;
}