C++ interop & P/Invoke


R

Raj

I want to understand why C++ interop has better performance than P/Invoke.
Can someone explain in detail.

Thanks
 
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B

Ben Voigt [C++ MVP]

Raj said:
I want to understand why C++ interop has better performance than P/Invoke.
Can someone explain in detail.

Because P/Invoke does a lot of extra stuff (pinning, blitting, error
checking, etc.)

C++ interop just pushes the parameters on the stack and calls the function.
Ok, some things still need to be converted or pinned, but with C++ interop
you can convert once and call a whole bunch of APIs, with P/Invoke EVERY
parameter passed by address gets pinned and unpinned on EVERY call, copied
and copied back, etc. Or C++ interop can avoid the pinning problem entirely
by creating POD structures on the native heap where they never move around.

Plus the C++/CLI compiler inherited a lot of very complicated optimization
logic that .NET hasn't duplicated yet.
 

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