Question

Good Morning.

I’ve got the following definition (this program was created by the guy who worked here before me) on a Visual Studio 2008 solution with c++:

[DllImport("msvcr70.dll", CallingConvention = CallingConvention::Cdecl)]
extern int _fpreset();

This line works perfect and I can call the _fpreset on the code.

Since we need to implement this as a 64 bits application I installed the Visual Studio 2010. Once we download the solution from the repository it ask me to do a conversion in order to work. I click yes and when I try to compile the program I get the following error:

error C2556:'int _fpreset(void)': overloaded functions only differ by return type with 'void _fpreset(void)'

When I try again in visual studio 2008 it works perfectly…

Any ideas why it doesn’t work on 2010?

Answer 1

The declaration is just wrong. You are now being reminded about it because some other VS2010 .h file you #include pulls in float.h, the header file that declares _fpreset(). Which gives the proper declaration of this CRT function with a return type of void.

You should delete this [DllImport] declaration, not just because it is wrong but it also gives your program a dependency on the ancient VS2002 CRT (msvcr70.dll). Add this to whatever source code file that actually calls _fpreset():

 #include <float.h>

Calling _fpreset() in managed code is pretty iffy, only do so when you are calling native code that messes up the FPU control word.