Re: How to properly fix memory leak

Hi, Lauren’s,

On Sat, Apr 26, 2025 at 3:30 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
wrote:

> On Fri, 2025-04-25 at 22:24 -0500, Igor Korot wrote:
> > Hi, ALL,
> >
> > [code]
> > auto res = PQexec( m_db, m_pimpl->m_myconv.to_bytes( query.c_str()
> > ).c_str() ); /* ask for binary results */
> > if( PQresultStatus( res ) != PGRES_TUPLES_OK )
> > {
> > auto err = m_pimpl->m_myconv.from_bytes( PQerrorMessage( m_db )
> );
> > errorMsg.push_back( L"Update validation table: " + err );
> > result = 1;
> > }
> > else
> > {
> > for( int i = 0; i < PQntuples( res ); i++ )
> > {
> > auto temp1 = 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]
> >
> > I ran this code on MSVC 2017 with VLD and according to the VLD report I
> have
> > a memory leak on the line indicated.
> >
> > Should I call PQclear() on every iteration of the loop?
> >
> > 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_tablespaces.push_back().

No, it is not spurious.
I’m getting it every time I run the program.

The m_tablespaces variable is declared as “std::vector<std::wstring>. No
pointer is involved.
I don’t see how it can produce the leak…

Thank you.

>
> Yours,
> Laurenz Albe
>