check compatability of a shared library before dynamically loading it

I have a program and bunch of "plug-ins" (shared libraries) that the main program loads on request during the runtime.

The plug-ins can access all the internal global data-structures/functions of the program, so there is no option to keep version for each time the internal data-structures changed.

I'm seeking f开发者_运维技巧or a way, that the main program can check if the plug-in it tries to load is supported (uses the appropriate data-structures).

Is there a creative way you can think of, doing this?

Have a function in the plugin returns information about the version of the protocol its support (The protocol of a plugin isn't restricted to what it provides, it is also what is required from the calling program.)

AProgrammer's answer (or simply exporting a global variable with the version number) will work, but bear in mind that no solution is foolproof or safe against malicious plugin files. Loaded modules run in the same memory space as your program, with the same privileges, and unfortunately the dynamic loader will happily run global constructors in the plugin before you are able to query the version or perform any checking yourself. (Grumble anyone have a link to Global Constructors Considered Harmful?)

In any case, if the plugin architecture is your design, I would highly recommend you ban any use of global constructors in specification for plugins. Of course you can't enforce this at runtime, but at least then you can blame any plugin author who breaks things for violating the contract.