Re: libpq error message deallocation

2012/12/4 icholy <ilia(dot)choly(at)gmail(dot)com>

> PQerrorMessage function return char const*
>
> char const* msg = PQerrorMessage(conn);
>
> Now since it's const, I don't think I should be deallocating it and I've
> never seen that done in any examples. But then, when and how does it get
> freed?
>
> At first I thought it gets deallocated once another error message is
> requested but that's not the case.
>
> // cause some error
> char const* msg1 = PQerrorMessage(pgconn);
>
> // cause another error
> char const* msg2 = PQerrorMessage(pgconn);
>
> // still works
> std::cout << msg1 << msg2 << std::endl;
>
> Can someone shed some light on this for me?

PQerrorMessage() returns pointer to the last allocated string
from the PGConn. The memory on this string will be deallocated
with PQfinish().
In the above case, msg1 is invalid pointer and you just got lucky.
Please, see description of PQerrorMessage() here
http://www.postgresql.org/docs/9.2/static/libpq-status.html

// Dmitriy.