[erlang-bugs] Hipe/native and reloading modules

[Bjorn Gustavsson]

We are aware that native code does not follow the usual rules for code reloading.
For technical reasons, in releases up to R11B it was not possible to correct this
deficiency. In R12B it will be possible, but the correction will be probably be done
in a later R12B release, not in the initial R12B-0 release.

/Björn

"Philip Smolen" <erlang@REDACTED> writes:

> I noticed something strange when I use the "native" option to compile my
> code.  Code reloading doesn't work the same way as when I don't specify
> "native".  Here's some sample code.
> 
>  
> 
> -module(reload).
> 
> -export([show/0, loop/0, version/0]).
> 
>  
> 
> show() -> spawn(fun loop/0).
> 
>  
> 
> loop() ->
> 
>   io:format("This process: ~p, Most current version: ~p ~n",
> 
>             [version(), reload:version()]),
> 
>   receive
> 
>     reload -> reload:loop();
> 
>     exit -> void
> 
>   after 5000 ->
> 
>     loop()
> 
>   end.
> 
>  
> 
> %% Change this each time:
> 
> version() -> 22.
> 
>  
> 
> When I don't use the native mode, it works as documented.  When I change the
> version number and say "c(reload)" the first version number stays the same
> and the second version number is incremented.
> 
>  
> 
> If I say "c(reload, native)" then it acts strange.  In that case both
> version numbers change to the latest one.  More precisely:
> 
> *	The recursive call to loop() always calls the original version of
> the code, as it should.  (Change the io:format statement if you want to
> verify that.)
> *	The recursive call to reload:loop() always calls the most recent
> version of the code, as it should.
> *	The call to reload:version() always calls the most recent version of
> the code, as it should.
> *	The call to version() works differently in different cases.  If you
> compiled without the native switch, it calls the original version of the
> code, as it should.  If you compiled with the native switch, it incorrectly
> calls the latest version.
> 
>  
> 
> I noticed something else that was strange, although I'm not sure if it's a
> bug or a feature.  When I don't use the "native" switch, I can see that
> there are only two versions of the code.  Erlang kills my process if it's
> using code that's too old, exactly as documented.  However, if I compile
> with the "native" switch then Erlang never kills my old code.
> 
>  
> 
> I'm running otp_src_R11B-5.tar.gz on Fedora.
> 
>  
> 
> PS The native option makes things work much faster!
> 
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-- 
Björn Gustavsson, Erlang/OTP, Ericsson AB