Can I preserve the last-error code before TraceMessage is called?

By default, TraceMessage is called by using the WPP_TRACE macro. In versions of Windows earlier than Windows Vista, the last-error code was overwritten by TraceMessage.

Starting with Windows Vista, you can preserve the last-error code by defining a custom WPP_TRACE macro. You must define your version of this macro before you include the trace message header (.tmh) file in the source file of your trace provider, such as a kernel-mode driver or user-mode application..

The following examples show how you can preserve the last-error code before you call TraceMessage:

• Make a wrapper to TraceMessage that is called from the WPP_TRACE macro. You can then call TraceMessageVa, from the wrapper function.

  The following example shows how to write a wrapper to TraceMessage:

  #define WPP_TRACE WppTraceMessageWrapper
  DWORD
  WppTraceMessageWrapper(
      __in TRACEHANDLE LoggerHandle,
      __in ULONG MessageFlags,
      __in LPCGUID MessageGuid,
      __in USHORT Message Number,
      ...)
  {
      DWORD TraceError = ERROR_SUCCESS;
      DWORD LastError = ERROR_SUCCESS;
      va_list Args = NULL;
  
      LastError = GetLastError();
  
      va_start(Args, Message Number);
      TraceError = TraceMessageVa(LoggerHandle, MessageFlags, MessageGuid, Message Number, Args);
      va_end(Args);
  
      SetLastError(LastError);
   return TraceError;
  }
  

• Modify the WPP_TRACE macro, as shown in the following example:

  #define WPP_TRACE(...)                              \
   do                                              \
      {                                               \
          DWORD LastError = GetLastError();           \
          TraceMessage(__VA_ARGS__);                  \
          SetLastError(LastError);                    \
      }                                               \
   while (FALSE, FALSE)
  

  Note   This method increases the code size of your binary files because the same code will be generated for each WPP_SF function.