Dynamic array implementation in pure C23. Type agnostic and macro based.

da_macro.c

#include <stdio.h>
#include <stdlib.h>

#define DA_INIT_CAP 256U // Initial Capacity

// Define the structure
#define DA_DEFINE(name, type)                   \
    typedef struct {                            \
        type *items;                            \
        size_t count;                           \
        size_t capacity;                        \
    } name



// Initialize the structure members
#define da_init(xp)                             \
    do {                                        \
        (xp)->items = nullptr;                  \
        (xp)->count = 0;                        \
        (xp)->capacity = 0;                     \
    } while (0)

// Next Capacity: increase by 1.5 for smaller size & for bigger increases by 2
#define next_capacity(curr)  ((curr) ? (((curr) < 1024) ? ((curr) * 3/2) : (curr) << 1): DA_INIT_CAP)

// da_append: append to the dynamic array
#define da_append(xp, x)                                                \
    do {                                                                \
        if ((xp)->count >= (xp)->capacity) {                            \
            (xp)->capacity = next_capacity((xp)->capacity);             \
            void *ptr = realloc((xp)->items, (xp)->capacity * (sizeof(*(xp)->items))); \
            if (ptr == nullptr) {                                       \
                fprintf(stderr, "Memory allocation failed!\n");         \
                exit(EXIT_FAILURE);                                     \
            }                                                           \
            (xp)->items = ptr;                                          \
        }                                                               \
        (xp)->items[(xp)->count++] = (x);                               \
    } while (0)

// Free Dynamic Array
#define da_free(xp)                             \
    do {                                        \
        free((xp)->items);                      \
        (xp)->items = nullptr;                  \
        (xp)->count = 0;                        \
        (xp)->capacity = 0;                     \
    } while (0)

DA_DEFINE(Integer, int);

int main(void)
{
    Integer xs = {};
    da_init(&xs);
    for (int i = 0; i < 10; i++) {
        da_append(&xs, i);
    }

    for (size_t i = 0; i < xs.count; i++) {
        printf("%d\n", xs.items[i]);
    }
    da_free(&xs);
    return 0;
}