[Lldb-commits] [PATCH] Fix showing children of synthetic providers for void*

Bruce Mitchener bruce.mitchener at gmail.com
Sun Jun 22 17:10:11 PDT 2014

On Sun, Jun 22, 2014 at 11:29 PM, Enrico Granata <egranata at apple.com> wrote:

> Bruce,
> your patch seems to essentially implement the algorithm "display children
> of pointer types if within the pointer depth OR there is a formatter that
> wants them shown"
> That's somewhat worrisome. The reason for having a pointer depth is that
> pointers potentially introduce recursion - i.e. you can have a pointer that
> points to itself. Limiting how deep you look into pointer values has the
> benefit that lldb will not hang in such situations trying to display an i
> infinitely recursive structure - which is especially useful if the infinite
> recursion was accidental and unexpected.

That isn't the case with my patch as I understand things.

Looking at the code, but stripped of comments:

ValueObjectPrinter::ShouldPrintChildren (bool is_failed_description,
                                         uint32_t& curr_ptr_depth)
    const bool is_ref = IsRef ();
    const bool is_ptr = IsPtr ();

    if (is_failed_description || m_curr_depth < options.m_max_depth)
        bool print_children = false;
        if (is_ptr || is_ref)
            AddressType ptr_address_type;
            if (m_valobj->GetPointerValue (&ptr_address_type) == 0)
                return false;

            else if (is_ref && m_curr_depth == 0 && curr_ptr_depth == 0)
                curr_ptr_depth = 1;

            print_children = (curr_ptr_depth > 0);

        TypeSummaryImpl* entry = GetSummaryFormatter();

        return (print_children || !entry ||
entry->DoesPrintChildren(m_valobj) || m_summary.empty());
    return false;

You can see that my change is squarely within the depth check, so it won't
allow infinite recursion.  If m_curr_depth >= options.m_max_depth, it will
still return false.

The only situation where my patch actually changes things with regards to
pointer depth is that now, a pointer at depth 0 will result in checking the
summary formatter.

 - Bruce
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