Re: How to check dll version?

"Alex Blekhman" <>
Fri, 20 Jul 2007 16:06:12 +0300
"bucher" wrote:

Now, if in main application, I only need to create an
interface for every dll. I don't have to write bunch of
"GetProcAddess". If I want to add more export functions, I
should update the interface class. What I worried about is
if I use the old dll, main application will not report any
errors when call "CreateInstance". It will report an error
when I call the new function. Is there any method to check
whether the dll is consistent with the interface file?

I should warn you that exporting classes from DLL, besides
the advantages you mentiond, has following drawbacks:

1. Both DLL and its client must use C++.

2. Both DLL and its client must use the same version of the
compiler in order to be compatible. There is no binary
compatibility for C++ code.

Regarding your versioning problem there is no ultimate
solution. Usually, once interface is published, it cannot
change (like in COM). Interface is a contract that you
cannot breach unilaterally. If you need to add new methods,
then make new interface. For example,

class IHardwareInterface2
    // all methods from IHardwareInterface

    // new methods
    virtual DWORD NewMethod() = 0;

So, old clients will continue to use `IHardwareInterface'
while new clients will be aware of new functionality and use
new interfaces.


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