Function Pointers

[johnnymckinney2]

Hello. I haven't had much trouble with function pointers in the past, but now they are a major pain. Could anyone tell me what I am doing wrong in the below code and give a fixed version please. I get a compiler error that I will also post below. Thanks in advance.

int test(int x)
{
    return 0;
}

int function(char* string)
{
    //...
    return test; // Returns the address of test.  
}

int main(void)
{
    int (*pointer) (int);
    pointer = (void *)function("Hello World"); 
    //...
}

Error

 error: invalid conversion from `int' to `int (*)(int)'

How would I fix this. Its really giving me a headache. I've been trying to figure this out for hours now.

[Salem]

http://www.newty.de/fpt/index.html

The first thing I would suggest is always create typedefs for your function pointer types. They get pretty hairy at times, and there's always an excess of ( ) to deal with.

typedef int (*fnType)(int);

int test(int x)
{
    return 0;
}

fnType function(char* string)
{
    //...
    return test; // Returns the address of test.  
}

int main(void)
{
    fnType pointer;
    pointer = function("Hello World");
    return 0;
}

[brewbuck]

int main(void)
{
    int (*pointer) (int);
    pointer = (void *)function("Hello World"); 
    //...
}

You call function(). This returns an int. You cast this to a void * for some reason, then try to stick it in a function pointer. No wonder it doesn't work.

int main(void)
{
    int (*pointer)(int);
    pointer = (int (*)(int))function;
}

Try that.

[matsp]

And of course, assuming that an int is the same size as a pointer may not work right on all systems. It would be better to return a pointer of some type - perhaps a function pointer type - using typedef like Salem suggested, or like this:

int test(int x)
{
    return 0;
}

int (*)(int) function(char* string)
{
    //...
    return test; // Returns the address of test.  
}

int main(void)
{
    int (*pointer) (int);
    pointer = function("Hello World"); 
    //...
}

--
Mats