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

  • Artikel

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.