VS2013 C++ Compiler Mangling name defined with extern "C"

I'm trying to build a WIN32 console app that uses the current 2.12.28 ftd2xx.lib static library from FTDI. I'm using VS2013 and native unmanaged C++. My call looks like this.

#include "../ftd2xx.h"
 . . .
    DWORD port_count = 0;
    FT_STATUS status = FT_OK;
    status = FT_CreateDeviceInfoList(&port_count);

When I compile I get a link error

GetTopazVCP.obj : error LNK2019: unresolved external symbol __imp__FT_CreateDeviceInfoList@4 referenced in function "unsigned long __cdecl Get1stVirtualComPort(unsigned long *)" (?Get1stVirtualComPort@@YAKPAK@Z)

The unresolved symbol __imp__FT_CreateDeviceInfoList@4 appears to be a mangled name version of the FT_CreateDeviceInfoList function. So it's not being resolved in the ftd2xx.lib which uses C naming. What I don't understand is why the compiler mangled the name when the ftd2xx.h file has a conditional extern "C"

#ifdef __cplusplus
   extern "C" {
#endif
. . .
FTD2XX_API
    FT_STATUS WINAPI FT_CreateDeviceInfoList(
    LPDWORD lpdwNumDevs
    );
...
#ifdef __cplusplus
}
#endif

wrapping all the FT_??? declarations. I have confirmed that __cplusplus is defined during the compile. Any ideas what is causing the unexpected name mangling?

Solution

As ChronoKitsune pointed out in his comment there is no name mangling here. The problem was I was linking the static version of the FTDI library but the default for the ftd2xx.h header file is to declare the FT_??? functions as calls to the DLL version. When I replaced the ftd2xx.lib static version with the ftd2xx.lib DLL version it built successfully. FTDI only supplies one version of the ftd2xx.h header and looking closely inside it I discovered that if you want to use the static ftd2xx.lib you need to #define FTD2XX_STATIC before including ftd2xx.h

#define FTD2XX_STATIC
#include "ftd2xx.h"