Thread: Using function pointer within a struct

Dear,

I have an issue with function pointer in a struct

Consider, I have a struct

Code:

struct MyStruct {
int a;
void (*function1) ();
}

I have another function which use a function pointer as an argument:

Code:

void function2(void (*function) ());

Now, I create an instance of a struct:

Code:

MyStruct* struct1;

I also call malloc for struct1.

Now, I want to pass function1 of struct1 to function2. How can I do it?

I tried:

Code:

function2(struct1->function1);
or
function2(&(struct1->function1));
or even
function2(*(struct1->function1));

but all of them are error and gcc reports "dereferencing pointer incomplete type".

Please help me.
Thank you

Dear laserlight,

Thanks for your help.

I modified as you describe, but the error still happen.

Did you remember to assign the function pointer before trying to pass it?

Code:

struct1->function1 = testfn;

Still I can't duplicate a dereferencing error exactly.

Dear,

This is my source code:

Code:

//file: test2.c
#include "test2.h"

struct Person2 {
	Person* corePerson; //another struct, don't need to care
	unsigned int height;
	void (*notify_age) ();
};




void	person2_notify_person_age () { //focus to this function, please
	printf ("I am person2 and I received a notification\n");
	return;
}


Person2*	person2_create (unsigned int age, unsigned int height) {
	Person2*	tempPerson2;
	tempPerson2 = malloc (sizeof (Person2));
	tempPerson2->corePerson = person_create (age);
	tempPerson2->height = height;
	printf ("I am a 2nd newcomer with age: %d and height: %d\n", person_get_age(tempPerson2->corePerson),tempPerson2->height);
	
	tempPerson2->notify_age = person2_notify_person_age; //assign the function pointer to real function
	
	return tempPerson2;
}


//...
//some other functions

And this is my test:

Code:

#include "test2.h"
#include "test3.h"

int main () 
{
	struct Person2* testPerson2;
	struct Person2* tempPerson2;
	int i = 0;

	
	Person* testPerson;
	testPerson = person_create (20);
	
	testPerson2 = person2_create (30, 50);
	
	person_set_age (testPerson, 20, testPerson2->notify_age); //call function pointer, ERROR here
		
	
	return 0;
}

I defined struct Person2 in test2.c, and in test2.h, I called:
typedef struct Person2 Person2;

Dear laserlight

Can you guide me to solve this issue?

I tried to add the get function in test2.c:

Code:

void*	person2_get_function_pointer (Person2* person2) {
	return (person2->notify_age);
}

and then, modified the function pointer call in main.c

Code:

person_set_age (testPerson, 20, person2_get_function_pointer (testPerson2));

Now, there is not error, but the function does not run. Maybe it is a NULL pointer (I guess).

Dear laserlight

It's done now, I fixed it.

Thank you very very much.