Initialize int array in struct in C - c

Question

I have written a type:
typedef struct
{
int Tape[TAPE_SIZE];
int *Head;
int Tape_Count;
int Loop_Start_Count;
} Tarpit;
I try to initialize this type with the following function:
void Tarpit_Initialize(Tarpit Tarpit)
{
Tarpit.Tape_Count = 0;
Tarpit.Loop_Start_Count = 0;
int Index;
for(Index = 0; Index < TAPE_SIZE; Index++)
{
Tarpit.Tape[Index] = INITIAL_SIZE;
}
}
However, it does not seem to work. If I run this:
Tarpit Foo;
Tarpit_Initialize(Foo);
printf("Tarpit Initialization Test: \n");
int index;
for(index = 0; index < TAPE_SIZE ; index++)
{
if(Foo.Tape[index] == INITIAL_SIZE)
{
printf("%d: %d \n", index, Foo.Tape[index]);
}
else
{
printf("%d: %d !ERROR \n", index, Foo.Tape[index]);
}
}
I get several non-zero values (I have set #define TAPE_SIZE 10000 and #define INITIAL_SIZE 0)
Moreover, if I run the test without running Tarpit_Initialize(Foo), I get exactly the same results. The initializer does not seem to work. Why/how could I implement it in an other way? I would like to set every element of Foo.Tape to zero.
Problem solved!

Answer 1

You are passing Tarpit by value:
void Tape_Initialize(Tarpit Tarpit)
That means it is only a copy of Tarpit. You have to pass a pointer to it to be able to modify it.
void Tape_Initialize(Tarpit* Tarpit)
and pass it as pointer (note the name of the function called!):
Tape_Initialize(&Foo);
and the use the -> operator to modify it. For instance:
Tarpit->Tape_Count = 0;
Moreover, as "Elias Van Ootegem" pointed out, you should not use sizeof(Tarpit.Tape) to get the size of the array but TAPE_LENGTH that you defined. Because sizeof() will give you a size in bytes not in elements.

Answer 2

Have you checked the function u are calling ??
Its "Tarpit_Initialize(Foo);"
But the Function u are using it to initialize "void Tape_Initialize(Tarpit Tarpit)".
I think even what u have implemented should work fine .