Re: Lua 5.3 and C++ exceptions

[Ahmed Charles <acharles@...>]

In my experience, compiling lua as C++ is sufficient to make it exception safe. Exceptions and setjmp/longjmp require the same considerations with regard to cleaning up resources.

Besides, this should be fairly easy to test/verify.


On Mar 13, 2015, at 2:03 PM, Colin Hirsch <lua@colin-hirsch.net> wrote:

>> On 13 March 2015 at 16:21 Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
>> 
>>> That does look interesting, although we’d have to check whether it
>>> is possible for us to switch to LuaJIT. The last time I looked at it
>>> that was not possible for lack of 64bit integer support (unfortunately
>>> Lua’s default numeric type “double” is not at all appropriate
>>> to our applications, and our Lua 5.1 is configured to use int64_t
>>> instead, something that Lua is well designed to handle). However it
>>> seems that in the meantime LuaJIT has gained support for some boxed
>>> 64bit integers, which might be good enough if well integrated…
>> 
>> (Out of topic) Can you give a brief explanation about why you need
>> 64bit integer support? (I am writing something about the introduction
>> of integers in Lua 5.3, and it would be good to have some more concrete
>> examples of why people need 64bit integers.)
> 
> We have multiple places where 32bit integers are not sufficient, for example time values (think microseconds since 1970), some
> statistics where 32bits can easily overflow, and some network protocols that we access from Lua have 64bit integer fields.
> 
> (And while some of these integer use cases could fit into 64bit floating point variables, we really don't want to start using
> floating point to model integer values, in particular in an application that doesn't use floating point anywhere else.)
> 
> After give-or-take a decade of working on 64bit machines I don't even want to think about whether something fits into 32bits :-)
> 
> 
> Now regarding my initial question, do you have any intuition regarding how much is missing for making Lua exception safe? Is it just
> some small detail that could be fixed with a small change, or does it require extensive reworking?
> 
> I have studied the Lua source code on various occasions, and successfully changed a few things, but haven't grokked some of the
> overall concepts sufficiently well to answer this question myself.
> 
> Thanks, Colin
>