Re: [BUG] Assertion failures when unloading and reloading the "ffi" package
- From: Mike Pall <mike-1305@xxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 31 May 2013 23:28:34 +0200
agentzh wrote:
> package.loaded["ffi"] = nil
This isn't the proper way to unload a module, nor is it documented
as such. Certainly not for core modules.
[Actually, there's no safe way to unload arbitrary modules, even
for plain Lua. C modules may depend on each other and unloading
them in the wrong order will wreak havoc. And if there's still a
userdata with a __gc C function around and you remove the shared
library from the address space with the above method ... guess
what happens.]
> We really need this usage because it is handy to reload an external
> FFI-based Lua module without destroying and recreating the "world"
> (i.e., the whole Lua VM) during either Lua code development or hot
> code replacement in production. Or do you have better suggestions?
Sorry, but I guess unloading the FFI module would never work well.
There may still be cdata objects around, there may be JIT-compiled
code that depends on the FFI module, there are tons of internal
dependencies, etc.
I guess recreating the whole VM is the safest bet.
[That might still get you into trouble even without the FFI: it
unloads/reloads the binding libraries, but might not unload the
underlying C libraries (e.g. lua-zip + libzip). And even if you
manage to do that, some C libs do not take it well if they are
unloaded (though libzip is probably ok -- just an example).]
--Mike
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