Question

I’m writing a program for a “Set” data structure in C.

It’s working fine when one instance of Set is present, but it doesn’t work when two instances of Set are present.

Also my code for removing an element is not working when the candidate is the first element.

Can someone help me?

Here is the code:

• Set.h

• Set.c

• Test.c

Answer 1

First of all you passes pointer to set by value. I.e. instead of

void Set_Create (Set* set) {
     set = malloc(...); // Malloc here leads to memory-leak.
     //...
}

int main() {
     Set *set; // Some value like 0xdeadbeef pointing somewhere
     Set_Create (set);
     // set have still undefined value
}

use

Set *Set_Create () {
     Set *set = malloc(...);
     /// ...
     return set;
}

int main() {
     Set *set; // Some value like 0xdeadbeef pointing somewhere
     set = Set_Create ();
     // set point to new memory
}

or:

void Set_Create (Set *set) {
     // No malloc
     /// ...
     return set;
}

int main() {
     Set set; // Create on stack
     Set_Create (&set); // Initialize
     // ...
}

I’d advice re-reading chapter on pointers (don’t worry – they are considered hard but they are must for C programmers).