pnstrdup considered armed and dangerous

Hi,

A colleage of me just wrote innocent looking code like       char *shardRelationName = pnstrdup(relationName,
NAMEDATALEN);
which is at the moment wrong if relationName isn't preallocated to
NAMEDATALEN size.

/** pnstrdup*        Like pstrdup(), but append null byte to a*        not-necessarily-null-terminated input string.*/
char *
pnstrdup(const char *in, Size len)
{char       *out = palloc(len + 1);
memcpy(out, in, len);out[len] = '\0';return out;
}

isn't that a somewhat weird behaviour / implementation? Not really like
strndup(), which one might believe to be analoguous...

Greetings,

Andres Freund