Difference between IJW and #pragma unmanaged ?

anti AS

Hi guys In C++/CLI what is the difference between using the concept of IJW (It Just Works) and using pragma directive as following:

#pragma managed(push,off)
UnmanagedFunc(){
…native code …
}
#pragma managed(pop)

Does IJW is enabled automatically (so just need to write our native code) or we need to do something to make it works..?? In other mean, what is the advantage of IJW over using pragma directive or the other way around??

Nish Nishant

IJW is just a term they used back in 2003/2004 to talk about how the managed-unmanaged transitions and marshaling were smoothly handled for you by the compiler. No one uses the term these days, and instead people just say C++ interop to refer to anything where mixed-mode code comes into play. #pragma unmanaged is a pre-compiler directive that tells the compiler that any code in that block must be compiled natively (meaning no msil at all). It's mostly used to ensure that frequently used code is compiled for better performance (which usually implies native code generation).

Regards, Nish

Latest article: Code Project Posts Analyzer for Windows Phone 7 My technology blog: voidnish.wordpress.com

anti AS

Thanx Nish If I use standard C function inside CPP/CLI code .. like for example:

ManagedFunction(){
..... Managed Code .....
..... Managed Code .....
printf("I am standard C function!\n");
..... Managed Code .....
..... Managed Code .....
}

Does MSIL do something with the printf() function! (Notice that i did NOT use #pragma umanaged directive!) If MSIL will do nothing with printf() so (as i think) printf() will be compiled as native??So why I need to use #pragma umanaged directive.

Nish Nishant

The call to printf will be emitted via msil. The printf method itself will execute as native code (there will be a managed to unmanaged jump during execution). Now instead of printf, assume you were calling your own global function Foo. Now if you did not put Foo's definition in a #pragma unmanaged block, Foo itself will be compiled as msil. That's a scenario where you'd actually want to use #pragma unmanaged, particularly if you think Foo is a time-intensive function.

Regards, Nish

Latest article: Code Project Posts Analyzer for Windows Phone 7 My technology blog: voidnish.wordpress.com

anti AS

:thumbsup: Great man... It is more clear now. Thank you.