Robin Gareus 3da07e6736 Special case Lua copy-construction of trackable instances ...

This fixes an crashing issue with ArdourUI.SelectionList a bug
introduced in 6dc3bdf252 and 35dcd46d7d.

Since removal of the special cases in 35dcd46d7d, when using
a C-pointer in a std::list<>,
  std::list<class*>::push_back(TypeListValue)
TypeListValues<>'s Head was expanded to  "class*& const"
implied by void ::push_back(const T& value);

This resulted in lifetime issues with a classes that derive
from sigc::trackable (e.g. Ardour's Selection).
The reference leaves scope and isn't duplicated when it is pushed back
to the std::list<>.

The script scripts/select_every_2nd_region.lua crashed because entries
in the SelectionList were no longer valid.

Previously (before 6dc3bdf252) TypeListValues explicitly
copy-constructed the value to work around the lifetime issue.
This new solution bypasses the issue by directly using the c-pointer
without dereferencing it.

2019-04-12 05:45:27 +02:00

45 KiB

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