Re: [Enigma-devel] crashes on linux gcc exception handling

[Ronald Lamprecht]

Hi,

Daniel Heck wrote:
> > So currently there are three types of errors:
> > 1. Lua code internally raises an error. (Dispatch internally with
> > longjmp or c++ exceptions. If not caught by internally with a pcall, is
> > handed to Enigma which converts it to an exception and throws it.)
> > 2. C code raises a lua_error. This is handled exactly like the above.
> > 3. Enigma raises a C++ excepetion.
> I only want to make sure that errors that could (or should) be handled
> inside the Lua scripts _can_ be handled inside the Lua scripts.  For
> example, GetNamedObject() should probably continue to return nil if it
> is called with an unknown object name and not raise an error.  Error
> handling inside the levels should not suffer from the fact that we start
> to use exceptions more extensively inside the C++ engine.

Agreed. For common uncritical errors that do not leave the engine in an 
unconsistent state the usage of special return values is preferrable.

> > Note that this bug is affecting type 3 errors only. I suspect it is
> > potentially possible to use only type 2's. That would solve the problem
> > on Linux
> > and would allow lua scripts to trap errors.
> >
> > The only downside is that a lua program would trap an error that it is
> > incapable of handing. If it fails to rethrow the error in such a case it
> > would be bad. It could either crash, or it could result in the usefull
> > error message being replaced with a less useful one created by lua's
> > internals.

Currently only "enigma.SendMessage()" converts type 3 to type 2. With a 
proper use of the catch-statement in luaconf.h and perhaps 2 different 
runtime exceptions, one for fatal and one for uncritical exceptions, 
Daniel's proposal should be feasible.

> Agreed.  And I don't think there is any need for immediate action; but
> error handling inside the level code is something we should definitely
> keep in mind.

O.k. - let us switch the configure option to enable-cxxlua as default 
for all OS and keep in mind the possible improvement.

- Ronald