Why does printf work with managed Strings?

Question

we are currently digging through some really old C++/CLI-Code (Old Syntax .NET Beta) and were a bit surprised to see something like this:

System::String ^sou         


        

Answer 1

I believe it is because the compiler is turning it into this IL:

call vararg int32 modopt([mscorlib]System.Runtime.CompilerServices.CallConvCdecl) printf(int8 modopt([mscorlib]System.Runtime.CompilerServices.IsSignUnspecifiedByte) modopt([mscorlib]System.Runtime.CompilerServices.IsConst)*, ..., string)

Which ends up as a pinvoke call to printf, so the runtime is being a little sneaky by marshalling it for you. You are still in a managed runtime, and the runtime will provide marhsalling as a service when it's needed.

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Some notes:

It seems that clr!GenericPInvokeCalliHelper is doing this lifting on the x86 .NET 4 Workstation CLR.

the following doesn't work

That's because that is straight C++. It has no chance to go through marshalling because it isn't needed.