/CLRSUPPORTLASTERROR (Preserve Last Error Code for PInvoke Calls)

Članak
08/03/2021
2 min. za čitanje

/CLRSUPPORTLASTERROR, which is on by default, preserves the last error code of functions called through the P/Invoke mechanism, which allows you to call native functions in DLLS, from code compiled with /clr.

Syntax

/CLRSUPPORTLASTERROR{:NO | SYSTEMDLL}

Remarks

Preserving the last error code implies a decrease in performance. If you do not want to incur the performance impact of preserving the last error code, link with /CLRSUPPORTLASTERROR:NO.

You can minimize the performance impact by linking with /CLRSUPPORTLASTERROR:SYSTEMDLL, which only preserves the last error code for functions in system DLLs.

Note

Preserving the last error is not supported for unmanaged functions that are consumed by CLR code, in the same module.

For more information, see /clr (Common Language Runtime Compilation).

To set this linker option in the Visual Studio development environment

Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Select the Configuration Properties > Linker > Command Line property page.
Enter the option into the Additional Options box.

To set this linker option programmatically

See AdditionalOptions.

Examples

The following sample defines a native DLL with one exported function that modifies last error.

// CLRSUPPORTLASTERROR_dll.cpp
// compile with: /LD
#include <windows.h>
#include <math.h>

#pragma unmanaged
__declspec(dllexport) double MySqrt(__int64 n) {
   SetLastError(DWORD(-1));
   return sqrt(double(n));
}

The following sample consumes the DLL, demonstrating how to use /CLRSUPPORTLASTERROR.

// CLRSUPPORTLASTERROR_client.cpp
// compile with: /clr CLRSUPPORTLASTERROR_dll.lib /link /clrsupportlasterror:systemdll
// processor: x86
#include <windows.h>
#include <wininet.h>
#include <stdio.h>
#include <math.h>

#pragma comment(lib, "wininet.lib")

double MySqrt(__int64 n);

#pragma managed
int main() {
   double   d = 0.0;
   __int64 n = 65;
   HANDLE  hGroup = NULL;
   GROUPID groupID;
   DWORD   dwSet = 127, dwGet = 37;

   SetLastError(dwSet);
   d = MySqrt(n);
   dwGet = GetLastError();

   if (dwGet == DWORD(-1))
      printf_s("GetLastError for application call succeeded (%d).\n",
             dwGet);
   else
      printf_s("GetLastError for application call failed (%d).\n",
             dwGet);

   hGroup = FindFirstUrlCacheGroup(0, CACHEGROUP_SEARCH_ALL,
                           0, 0, &groupID, 0);
   dwGet = GetLastError();
   if (dwGet == 183)
      printf_s("GetLastError for system call succeeded (%d).\n",
             dwGet);
   else
      printf_s("GetLastError for system call failed (%d).\n",
             dwGet);
}

GetLastError for application call failed (127).
GetLastError for system call succeeded (183).