Writing to mmaped region cause segfault

[Alexey Suslikov]

Hello t...@.

On OpenBSD/amd64, doing something like
    char *buf = mmap(NULL, len + 1, PROT_READ | PROT_WRITE,
MAP_PRIVATE, some.fd, 0);
    buf[len] = '\0';
causes segfault on buf[len] = '\0' assignment if len = 16384.

However doing
    char *buf = mmap(NULL, len + 1, PROT_READ | PROT_WRITE,
MAP_PRIVATE, some.fd, 0);
    char *nbuf = malloc(len + 1);
    memcpy(nbuf, buf, len);
    nbuf[len] = '\0';
does not lead to a crash.

Is it expected behavior of mmap (alignment?) or usage of mmap is wrong?

Thanks.

Alexey