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From: Dominique Devienne <ddevienne@gmail.com>
Date: Mon, 16 Mar 2026 11:25:15 +0100
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Subject: Re: libpq usage from C++
To: Igor Korot <ikorot01@gmail.com>
Cc: "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Sat, Mar 14, 2026 at 5:41=E2=80=AFAM Igor Korot <ikorot01@gmail.com> wro=
te:
> Does anybody use libpq from C++?

Yes

> C++ introduces STL.
> C++ introduces smart-pointers.
> Is there a simple way of using those writing libpq communication?
> Or should I just forget about them and use good old "dump pointers"?

Using an existing wrapper is simplest, of course.
We wrote our own. To each its own. E.g.

PS: Avoid the fwd-decl by using the actual libpq headers instead.

extern "C" {

struct pg_conn;
struct pg_result;
typedef struct pg_conn PGconn;
typedef struct pg_result PGresult;
typedef struct _PQconninfoOption PQconninfoOption;
typedef struct pgNotify PGnotify;
void PQfreemem(void *ptr);
void PQclear(PGresult* res);
void PQfinish(PGconn* conn);
void PQconninfoFree(PQconninfoOption* conn);

} // extern "C"

namespace acme::postgresql {

struct PGDeleterFunctor {
    void operator()(PGresult* r) {
        if (r !=3D nullptr) {
            PQclear(r);
        }
    }
    void operator()(PGconn* c) {
        if (c !=3D nullptr) {
            PQfinish(c);
        }
    }
    void operator()(PQconninfoOption* c) {
        if (c !=3D nullptr) {
            PQconninfoFree(c);
        }
    }
    void operator()(PGnotify* n) {
        if (n !=3D nullptr) {
            PQfreemem(n);
        }
    }
};
using PGresult_uptr     =3D std::unique_ptr<PGresult,         PGDeleterFunc=
tor>;
using PGconn_uptr       =3D std::unique_ptr<PGconn,           PGDeleterFunc=
tor>;
using PGconninfo_uptr   =3D std::unique_ptr<PQconninfoOption, PGDeleterFunc=
tor>;
using PGnotify_uptr     =3D std::unique_ptr<PGnotify,         PGDeleterFunc=
tor>;

...
}

Then we have higher-level wrappers that compose those RAII low-level ones. =
--DD