How to call DLL exported functions with @<number> at end of function name from C

Question

I am trying to call functions from ntvdm.lib in Visual Studio 2019 using the Visual Studio 2017 - Windows XP (v141_XP) platform toolset, with the following defined:

#define _WIN32_WINNT 0x0501
#define i386

running dumpbin /exports on the LIB file I get the following output:

Microsoft (R) COFF/PE Dumper Version 14.29.30037.0
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file ntvdm.lib

File Type: LIBRARY

     Exports

       ordinal    name

                  _BlockWOWIdle@4
                  _CurrentMonitorTeb
                  _DBGNotifyDebugged@4
                  _DBGNotifyNewTask@8
                  _DBGNotifyRemoteThreadAddress@8
                  _DispatchInterrupts@0
                  _Dos_Flag_Addr
                  _DpmiSetIncrementalAlloc@4
                  _ExpLdt
                  _FlatAddress
                  _GetDOSAppName@4
                  _InitialVdmDbgFlags
                  _InitialVdmTibFlags
                  _IsCdRomFile@4
                  _MGetVdmPointer@12
                  _RedirectLongFileName@12
                  _RedirectShortFileName@12
                  _RegisterWOWIdle@0
                  _ResumeTimerThread@0
                  _SelectorLimit
                  _SetShadowDescriptorEntries@8
                  _ShortPathEnvVar@4
                  _Sim32pGetVDMPointer@8
                  _SoftPcEoi@8
                  _SuspendTimerThread@0
                  _VDDAllocMem@12
                  _VDDAllocateDosHandle@12
                  _VDDAssociateNtHandle@12
                  _VDDDeInstallIOHook@12
                  _VDDDeInstallMemoryHook@12
                  _VDDDeInstallUserHook@4
                  _VDDExcludeMem@12
                  _VDDFreeMem@12
                  _VDDIncludeMem@12
                  _VDDInstallIOHook@16
                  _VDDInstallMemoryHook@16
                  _VDDInstallUserHook@20
                  _VDDQueryDMA@12
                  _VDDReleaseDosHandle@8
                  _VDDReleaseIrqLine@8
                  _VDDRequestDMA@16
                  _VDDReserveIrqLine@8
                  _VDDRetrieveNtHandle@16
                  _VDDSetDMA@16
                  _VDDSimulate16@0
                  _VDDTerminateVDM@0
                  _VdmDbgAttach@0
                  _VdmGetParametersInfoError@0
                  _VdmMapFlat@12
                  _VdmParametersInfo@12
                  _VdmTraceEvent@12
                  _WOWSysErrorBox@20
                  _WaitIfIdle@0
                  _call_ica_hw_interrupt@12
                  _cmdCheckTemp@4
                  _cmdCheckTempInit@0
                  _cpu_createthread@8
                  _demClientErrorEx@12
                  _demFileDelete@4
                  _demFileFindFirst@12
                  _demFileFindNext@4
                  _demGetFileTimeByHandle_WOW@4
                  _demGetPhysicalDriveType@4
                  _demIsShortPathName@8
                  _demLFNCleanup@0
                  _demLFNGetCurrentDirectory@8
                  _demSetCurrentDirectoryGetDrive@8
                  _demWOWLFNAllocateSearchHandle@4
                  _demWOWLFNCloseSearchHandle@4
                  _demWOWLFNEntry@4
                  _demWOWLFNGetSearchHandle@4
                  _demWOWLFNInit@4
                  _fSeparateWow
                  _getAF@0
                  _getAH@0
                  _getAL@0
                  _getAX@0
                  _getBH@0
                  _getBL@0
                  _getBP@0
                  _getBX@0
                  _getCF@0
                  _getCH@0
                  _getCL@0
                  _getCS@0
                  _getCX@0
                  _getDF@0
                  _getDH@0
                  _getDI@0
                  _getDL@0
                  _getDS@0
                  _getDX@0
                  _getEAX@0
                  _getEBP@0
                  _getEBX@0
                  _getECX@0
                  _getEDI@0
                  _getEDX@0
                  _getEFLAGS@0
                  _getEIP@0
                  _getES@0
                  _getESI@0
                  _getESP@0
                  _getFS@0
                  _getGS@0
                  _getIF@0
                  _getIP@0
                  _getIntelRegistersPointer@0
                  _getMSW@0
                  _getOF@0
                  _getPF@0
                  _getSF@0
                  _getSI@0
                  _getSP@0
                  _getSS@0
                  _getZF@0
                  _host_CreateThread@24
                  _host_ExitThread@4
                  _host_com_close@4
                  _host_direct_access_error@4
                  _host_simulate@0
                  _pDeviceChain
                  _setAF@4
                  _setAH@4
                  _setAL@4
                  _setAX@4
                  _setBH@4
                  _setBL@4
                  _setBP@4
                  _setBX@4
                  _setCF@4
                  _setCH@4
                  _setCL@4
                  _setCS@4
                  _setCX@4
                  _setDF@4
                  _setDH@4
                  _setDI@4
                  _setDL@4
                  _setDS@4
                  _setDX@4
                  _setEAX@4
                  _setEBP@4
                  _setEBX@4
                  _setECX@4
                  _setEDI@4
                  _setEDX@4
                  _setEFLAGS@4
                  _setEIP@4
                  _setES@4
                  _setESI@4
                  _setESP@4
                  _setFS@4
                  _setGS@4
                  _setIF@4
                  _setIP@4
                  _setMSW@4
                  _setOF@4
                  _setPF@4
                  _setSF@4
                  _setSI@4
                  _setSP@4
                  _setSS@4
                  _setZF@4

  Summary

          BD .debug$S
          14 .idata$2
          14 .idata$3
           4 .idata$4
           4 .idata$5
           A .idata$6

The function definition I'm trying to call in VDDSVC.h is:

#define GetVDMPointer(Address, Size, Mode) Sim32GetVDMPointer(\
                        Address, Size, Mode)

However visual studio error is:

Error   LNK2019 unresolved external symbol _MGetVdmPointer referenced in function _VddDispatch

_MGetVdmPointer is in the lib file but referenced as _MGetVdmPointer@12

• I reviewed the options here but couldn't determine which one might apply in my scenario https://learn.microsoft.com/en-us/cpp/error-messages/tool-errors/linker-tools-error-lnk2019?view=msvc-170
• In Linker -> General -> Show Progress I tried setting /VERBOSE although no additional information was generated in the logs
• I tried changing calling convention to "__stdcall" in C/C++ -> Advanced Calling Convention
• I've tried changing files from .C to .CPP although get similar error (Although the symbol looked for is a c++ mangled style name)

Answer 1

The issue was calling convention needs to be modified to "__stdcall" in C/C++ -> Advanced Calling Convention

Which I had tried, however Visual Studio 2019 project properties was defaulting to configuration for "Release" build and not the current build type "Debug(Active)" which effectively made my initial change of that setting ineffective.

As suggested in comments by IInspectable:

When changing global project properties, always make sure the "Configuration" is set to "All Configurations" and "Platform" is set to "All Platforms"