CODEWITHSUNDEEP
arrayscfunctionpointersimplicit-conversion
MrBit
MrBit

Reputation: 300

A pointer to array of pointers to function

Let's say I have a function

int foo(void)
{
    printf("Hello world");
}

And I want to use a pointer to a function to point to foo().

typedef int (*f_ptr)(void);

Which one of those cases would I use for that purpose?

(A) f_ptr my_ptr = foo;
    my_ptr();

(B) f_ptr * my_ptr = foo;
    my_ptr();

Now if I have 10 functions foo1(), foo2() .. foo10() and I want to put them in an array and iterate through the array using a pointer to function, how would I do it?

f_ptr my_functions[10] =
{
    foo1,
    foo2,
    ..
    foo10,
};

(A) f_ptr my_ptr = my_functions;   
(B) f_ptr * my_ptr = my_functions;

    for (int x = 0; x < 10; x++)
    {
        my_ptr();
        my_ptr++;
    }

Upvotes: 1

Views: 71

Answers (1)

Vlad from Moscow
Vlad from Moscow

Reputation: 310980

For starters pay attention to that though this function

int foo(void)
{
    printf("Hello world");
}

has the return type int it returns nothing. Instead you could write for example

int foo(void)
{
    return printf("Hello world");
}

Nevertheless an array designator used in expressions with rare exceptions is converted to pointer to its first element.

So if the element type of the array

f_ptr my_functions[10];

is f_ptr then a pointer to elements of the array will look like

f_ptr * my_ptr = my_functions;

So for example you can write a loop using the pointer like

for ( size_t i = 0; i < 10; i++ )
{
    my_ptr[i]();
}

Or

for ( f_ptr *my_ptr = my_functions; my_ptr != my_functions + 10; ++my_ptr )
{
    ( *my_ptr )();
}

Upvotes: 1

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