sol2/docs/source/safety.rst

safety
======

Sol was designed to be correct and fast, and in the pursuit of both uses the regular ``lua_to{x}`` functions of Lua rather than the checking versions (``lua_check{X}``) functions. The API defaults to paranoidly-safe alternatives if you have a ``#define SOL_CHECK_ARGUMENTS`` before you include Sol, or if you pass the ``SOL_CHECK_ARGUMENTS`` define on the build command for your build system. By default, it is off and remains off unless you define this, even in debug mode. The same goes for ``#define SOL_SAFE_USERTYPE``.

Note that you can obtain safety with regards to functions you bind by using the :doc:`protect<api/protect>` wrapper around function/variable bindings you set into Lua.

``SOL_SAFE_USERTYPE`` triggers the following change:
	* If the userdata to a usertype function is nill, will trigger an error instead of letting things go through and letting the system segfault

``SOL_CHECK_ARGUMENTS`` triggers the following changes:
	* ``sol::stack::get`` (used everywhere) defaults to using ``sol::stack::check_get`` and dereferencing the argument. It uses ``sol::type_panic`` as the handler if something goes wrong.
	* ``sol::stack::call`` and its variants will, if no templated boolean is specified, check all of the arguments for a function call.
	* If ``SOL_SAFE_USERTYPE`` is not defined, it gets defined to turn it on

Remember that if you want these features, you must explicitly turn them on. Additionally, you can have basic boolean checks when using the API by just converting to a :doc:`sol::optional\<T><api/optional>` when necessary. Tests are compiled with this on to ensure everythign is going as expected.

Finally, some warnings that may help with errors when working with Sol:

.. warning::

	Do NOT save the return type of a :ref:`function_result<function-result>` with ``auto``, as in ``auto numwoof = woof(20);``, and do NOT store it anywhere. See :ref:`here<function-result-warning>`.