example of simple type generics in C

List.h

#ifndef LIST_H
#define LIST_H

#define LIST IntList
#define TYPE int
#include "ListImpl.h"
#undef LIST
#undef TYPE

#define LIST Vec2List
#define TYPE Vec2
#include "ListImpl.h"
#undef LIST
#undef TYPE

#define LIST FloatList
#define TYPE float
#include "ListImpl.h"
#undef LIST
#undef TYPE

#endif

ListImpl.h

#include <stdlib.h>

struct LIST {
    TYPE * data;
    size_t len;
    size_t max;
}

inline LIST LIST ## _create(size_t reserve) {
    LIST l = {};
    l.data = (TYPE *) malloc(reserve * sizeof(TYPE));
    l.max = reserve;
    l.len = 0;
    return l;
}

inline LIST LIST ## _add(LIST l, TYPE t) {
    if (l.len == l.max) {
        l.max *= 2;
        l.data = (TYPE *) realloc(l.data, l.max * sizeof(TYPE));
    }

    l.data[l.len] = t;
    ++l.len;

    return l;
}

inline LIST LIST ## _remove(LIST l, size_t index) {
    --l.len;
    for (int i = index; i < l.len; ++i) {
        l.data[i] = l.data[i + 1];
    }

    return l;
}

//removes elements in range [first, last)
inline LIST LIST ## _remove(LIST l, size_t first, size_t last) {
    size_t range = last - first;
    l.len -= range;
    for (int i = first; i < l.len; ++i) {
        l.data[i] = l.data[i + range];
    }

    return l;
}

inline LIST LIST ## _shrink_to_fit(LIST l) {
    l.data = (TYPE *) realloc(l.data, l.len * sizeof(TYPE));
}

inline LIST LIST ## _destroy(LIST l) {
    free(l.data);
}