source: vendor/python/2.5/Python/asdl.c

#include "Python.h"
#include "asdl.h"

asdl_seq *
asdl_seq_new(int size, PyArena *arena)
{
        asdl_seq *seq = NULL;
        size_t n = sizeof(asdl_seq) +
                        (size ? (sizeof(void *) * (size - 1)) : 0);

        seq = (asdl_seq *)PyArena_Malloc(arena, n);
        if (!seq) {
                PyErr_NoMemory();
                return NULL;
        }
        memset(seq, 0, n);
        seq->size = size;
        return seq;
}

asdl_int_seq *
asdl_int_seq_new(int size, PyArena *arena)
{
        asdl_int_seq *seq = NULL;
        size_t n = sizeof(asdl_seq) +
                        (size ? (sizeof(int) * (size - 1)) : 0);

        seq = (asdl_int_seq *)PyArena_Malloc(arena, n);
        if (!seq) {
                PyErr_NoMemory();
                return NULL;
        }
        memset(seq, 0, n);
        seq->size = size;
        return seq;
}