Double pointer to function

Question

I need to create this function:

void lpLoadFileFunc(int (*loadFile)(char *filename, FILE **file))

To do this I must first create this function:

int loadFile (char *filename, FILE **file))

This function should upload a file and return if the load was successful.

But I fail to understand why using double pointer.

Can you help?

Perhaps with a given filename, a search may yield multiple files? The FILE **file would allow you to retrieve an array of pointers, each pointing to a different file. — ryyker, Apr 23 '15 at 15:41
or the loadFile function is 'returning' the FILE * pointer of the open file. We need to see the source of loadFile — pm100, Apr 23 '15 at 16:06

2501 · Answer 1 · 2015-04-23T15:58:36.360

C is a pass by value. When you pass a variable to a function it gets copied and a change of that copy will not change the original variable. You can however pass an address of a variable, the function will get a pointer to that variable, which enables you to change it. Don't forget that a pointer is still a variable and if you want to change a pointer you need a double pointer.

void Test( int value , int* pointer )
{
    value = 1 ;
    *pointer = 1 ;
}

int one = 0 ;
int two = 0 ;

Test( one , &two ) ;

printf( "%d %d\n" , one , two ) ;

As you can see, one did not change.

Double pointer to function

1 Answers1