typed_array_union.c

typedef struct {
    void *data;
    size_t num_items;
    size_t max_items;
} array_t;

// ...

typedef struct {
    union {
        struct {
            // Alias the fields of the untyped array with typed pointers and appropriate names.
            char **files;
            size_t num_files;
        };
        array_t files_array;
    };
} file_list_t;

void file_list_init(file_list_t *file_list) {
    array_init(&file_list->files_array, sizeof(char *));
}

void file_list_add(file_list_t *file_list, char *filename) {
    array_add(&file_list->files_array, &filename, sizeof(char *));
}