av_push, as documented, takes ownership of one reference count. If you mortalise the scalars, their refcnt will be reduced to zero even though the array still hold a reference to them. Bug. Don't mortalise them. 

AV* return_an_array() 
{
    AV* av = newAV();
    av_push( av, newSViv( 7  ) );
    av_push( av, newSviv( 42 ) );
    return av;
}

[download]

The thing is, Perl has a bug of its own. The output typemap for AV*

  1. Creates a reference to the AV.
  2. Increases the refcount of the AV (REFCNT=2: BUG!!!)
  3. Mortalises the reference.

So the AV and thus its content leak. Avoid it by using the following: 

SV* return_an_array() 
{
    AV* av = newAV();
    av_push( av, newSViv( 7  ) );
    av_push( av, newSviv( 42 ) );
    return newRV_noinc(av);
}

[download]

The output typemap for SV* will mortialise the reference.

In reply to Re: When to (and not to) use sv_2mortal() [first question only] by ikegami
in thread When to (and not to) use sv_2mortal() by davido

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