Re: what to check for loaded plugin?

From:
Le Chaud Lapin <jaibuduvin@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 8 Jul 2007 07:45:09 CST
Message-ID:
<1183835526.580023.143160@22g2000hsm.googlegroups.com>
On Jun 23, 5:40 pm, Lukasz Michalski <l...@zork.pl> wrote:

Hi,

I have library that defines some interface, and plugins contains
implementations for that interface. Plugins are loaded by main library
at runtime.

My question is what should I check to be pretty safe that loaded plugin
will not crash application that uses my library. I don't care about
checking if particular plugin _can_ be loaded by main library, I want to
raise error when _already loaded_ plugin will crash program because of
different build configuration between plugin and library.


Well, you could do what COM does on Window, which is check every
single interface against a GUID. But as you probably imagined, there
is really nothing you can do. It would be nice if your library could
do a frisk of the plug-in before using it, but of course, software is
not human. Anything can happen.

Obviously I need to check ABI of library against ABI of plugin, which I
version myself. I need to check build configuration's that I support
(debug, release for VC++ at least).

What else should be checked?
Should I check compiler version or is it safe to ignore it?


Checking the compiler version would be "yucky" from an engineering
point of view.

My library aims to be cross-platform, but currently I support only gcc
and VC compilers.

Many thanks for any help or references to articles regarding this topic,


You already know that there is no way that you can keep the plug-in
from crashing your application. Beyond that, for each interface, you
can pick a large, pseudo-random 128-bit (or even 64-bit) number and
compare what your library expects with what the plug-in provide. A
Nonce class will help:

struct Nonce
{
   char buffer[16];
   Nonce ()
   {
     // Randomize buffer.
   }
   bool operator == (Nonce &that);
   bool operator != (Nonce &that);
   // etc.
} ;

-Le Chaud Lapin-

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