Question

So i thought this would be straight forward but i keep getting compile errors, which probably means i am doing something stupid.

So i am using C and i want to save a pointer to a function in a global variable.

As a test case i have three files. Test.c, Test.h and FunctionPtr.c

Test.h goes like this

void (*MyCallBack)(void);

int SetFunc( void (*CallBackArg)(void));
void CallFunc();

Test.c Goes like this

#include <stdio.h>
#include <stdlib.h>
#include "test.h"
void SetFunc( void (*CallBackArg)(void)){

    printf("Set CallBack\n");
    MyCallBack=CallBackArg;
}

void CallFunc(){
    printf("In Call Func\n");
    MyCallBack();
}

and FunctionTest.c goes like this

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


void MyFunc(){
    printf("Work!\n");
}
int main()
{
    SetFunc(MyFunc);
    CallFunc();

}

When i compile using gcc FunctionTest.c test.c test.h -o FunctionTest

I get the following error…

test.c:4: error: conflicting types for ‘SetFunc’
test.h:4: note: previous declaration of ‘SetFunc’ was here

I cant figure out what i am doing wrong? Perhaps i am not declaring the Global Pointer right?

Answer 1

int SetFunc( void (*CallBackArg)(void));

void SetFunc( void (*CallBackArg)(void))

The return types are different, that’s your problem. You have to declare it the same way in the header as in the .c file.