Message-ID: <0a2be546e57d6088acf734f8d6a308a984e7171b.camel@cybertec.at>
Subject: Re: How to properly fix memory leak
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Igor Korot <ikorot01@gmail.com>, "pgsql-generallists.postgresql.org"
	 <pgsql-general@lists.postgresql.org>
Date: Sat, 26 Apr 2025 22:30:28 +0200
In-Reply-To: <CA+FnnTyR9AoJx-3zuvgudeYmUTiNcfpAucUh0ZTcs=Ajy49qVA@mail.gmail.com>
References: 
	<CA+FnnTyR9AoJx-3zuvgudeYmUTiNcfpAucUh0ZTcs=Ajy49qVA@mail.gmail.com>
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On Fri, 2025-04-25 at 22:24 -0500, Igor Korot wrote:
> Hi, ALL,
>=20
> [code]
>     auto res =3D PQexec( m_db, m_pimpl->m_myconv.to_bytes( query.c_str()
> ).c_str() );      /* ask for binary results */
>     if( PQresultStatus( res ) !=3D PGRES_TUPLES_OK )
>     {
>         auto err =3D m_pimpl->m_myconv.from_bytes( PQerrorMessage( m_db )=
 );
>         errorMsg.push_back( L"Update validation table: " + err );
>         result =3D 1;
>     }
>     else
>     {
>         for( int i =3D 0; i < PQntuples( res ); i++ )
>         {
>             auto temp1 =3D m_pimpl->m_myconv.from_bytes( PQgetvalue(
> res, i, 1 ) );
>             m_tablespaces.push_back( temp1 );
>         } // this line gives a leak according to VLD
>     }
>     PQclear( res );
>     return result;
> [/code]
>=20
> I ran this code on MSVC 2017  with VLD and according to the VLD report I =
have
> a memory leak on the line indicated.
>=20
> Should I call PQclear() on every iteration of the loop?
>=20
> And I hope I handle the error cae properly...

No, PQclear() would cause an error (double free).

If it is not a spurious complaint, the leak would have to be in m_tablespac=
es.push_back().

Yours,
Laurenz Albe