/CLRSUPPORTLASTERROR (Preserve Last Error Code for PInvoke Calls)

The latest version of this topic can be found at -CLRSUPPORTLASTERROR (Preserve Last Error Code for PInvoke Calls).

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. A system DLL is defined as one of the following:

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

To set this linker option in the Visual Studio development environment

1. Open the project's Property Pages dialog box. For details, see Setting Visual C++ Project Properties.

2. Click the Linker folder.

3. Click the Command Line property page.

4. Type the option into the Additional Options box.

To set this linker option programmatically

• See AdditionalOptions.

Example

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));  
}  

Example

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).  

See Also

Setting Linker Options
Linker Options