Simple vector implementation in C

vector.c

#include <stdlib.h>
#include "vector.h"

vector make_vector() {
    vector vec = {
        (int*)malloc(BUFSIZE*sizeof(int)),
        BUFSIZE,
        0
    };
    return vec;
}

void reallocate(vector* vec) {
    int* new_buf = (int*)malloc(2*vec->bufsize*sizeof(int));
    for (int i = 0; i < vec->bufsize; i++)
        new_buf[i] = vec->buffer[i];
    vec->bufsize *= 2;
    free(vec->buffer);
    vec->buffer = new_buf;
}

void push(vector* vec, int el) {
    vec->buffer[vec->ptr++] = el;
    if (vec->ptr == vec->bufsize)
        reallocate(vec);
}

int pop(vector* vec) {
    return vec->buffer[--vec->ptr];
}

int size(vector* vec) {
    return vec->ptr;
}

int peek(vector* vec) {
    return vec->buffer[vec->ptr-1];
}

int empty(vector* vec) {
    return size(vec) == 0;
}

vector.h

typedef struct
{
    int* buffer;
    int bufsize;
    int ptr;
} vector;

vector make_vector();
void push(vector* vec, int el);
int pop(vector* vec);
int size(vector* vec);
int peek(vector* vec);