ctypes:Multiple library access problem

[Dave Angel]

Massi wrote:
> Hi everyone,
>
> in my script I need to execute multiple separated loading of the same
> dll library, in order to handle the internal variables with different
> threads.
> Consider the followin piece of code:
>
> lib1 = cdll.LoadLibrary("MyLib.dll"))
> lib2 = cdll.LoadLibrary("MyLib.dll"))
>
> lib1.var1 = 0
> lib2.var1 = 1
>
> Now, if I print the value of lib1.var1 I get 1, that is lib1 and lib2
> point to the same memory space. Is there a way to create "different
> instances" of the same library? Or, alternatively, does it exist any
> workaround to avoid lib1 and lib2 share the same memory space?
>
> Thanks in advance.
>
>   
Windows will not load the same DLL twice into the same process in two 
different places.  When it detects that it's the same one, it simply 
returns the same handle as the earlier one, without any loading or 
initializing.

With some DLL's, you might get away with copying it to a different 
filename, and then loading each as an independent item.  But unless you 
wrote it yourself, or it has been documented for that behavior, you're 
taking a big risk.

On the other hand, if the DLL was written with threading in mind, then 
it'll get notified for each new thread you create, and it can manage TLS 
(thread local storage) rather than using extern vars.  I have no idea 
how to get at those from Python, however.

DaveA