[Vm-dev] mantis http://bugs.squeak.org/view.php?id=7349

[Andreas Raab]

Igor Stasenko wrote:
> Interpreterproxy structure v.2.1 contains only 3 function pointers:
> 
> 	sqInt (*minorVersion)(void);
> 	sqInt (*majorVersion)(void);
> 
> /* IMPORTANT!!!
> *	The rest of functions can be obtained by plugin by calling a
> getVMFunctionPointerBySelector function.
> *	The need in defining additional functions in this struct is gone forever
> */
> 	void * (*getVMFunctionPointerBySelector)(char * selector);
> 
> 
> as you see, in case of Hydra, going past v.2.1. is quite pointless. :)

No, you're completely missing the point of the version identifier. It 
has two roles: One is to identify which set of functions a plugin can 
expect which allows us to provide compatibility functions since the 
proxy interface is documented. So one very good reason is documentation.

Second, there is a higher level notion of whether something is 
compatible or not - for example the return value from certain functions 
change in a 64 bit image accordingly (I don't even know how a 32 bit 
plugin is prevented from interacting with a 64 bit image today). 
Sometimes you really need a high-level bit that tells you that the world 
has changed even if the names stay the same.

It makes absolutely no sense to say "oh, we'll all just look it up and 
then somehow it's going to magically work". Version information is 
*critical* if you want to play things together in the long term - it has 
allowed us to have a very smooth ride for a very long time in this area 
and I wish Squeak would have more of that in general.

Cheers,
   - Andreas