从dll使用Pantheios日志记录框架

Question

我正在尝试从c++动态链接库内部使用pantheios日志记录框架。我已经成功地构建了动态链接库，并且它通过我的测试应用程序(C++ MFC应用程序)执行。

我使用了隐式链接，如下所示：

#include <pantheios/implicit_link/core.h>
#include <pantheios/implicit_link/fe.simple.h>
#include <pantheios/implicit_link/be.console.h>

我的DllMain使用以下调用初始化pantheios：

extern "C" const char PANTHEIOS_FE_PROCESS_IDENTITY[] = "FinishingLineController";

BOOL APIENTRY DllMain( HMODULE hModule,
                   DWORD  ul_reason_for_call,
                   LPVOID lpReserved)
    {
        switch (ul_reason_for_call)
        {
        case DLL_PROCESS_ATTACH:
            {
            int panres =  pantheios::pantheios_init(); 

            if(panres < 0)
            {
                fprintf(stderr, "Failed to initialise the Pantheios libraries: %s\n", 
                        pantheios::pantheios_getInitErrorString(panres));

                return FALSE;
            }
            }
            break;
        case DLL_THREAD_ATTACH:
            break;
        case DLL_THREAD_DETACH:
            break;
        case DLL_PROCESS_DETACH:
            pantheios::pantheios_uninit();
            break;
        }
        return TRUE;
    }

当我执行下面的代码时，我得到一个

Microsoft C++ exception: stlsoft::winstl_project::windows_exception at memory location 0x0013da84

pantheios::log_DEBUG("Test logging");

我尝试使用显式链接，但没有任何结果。

Answer 1

一些进一步的测试表明，如果我将dll链接到控制台应用程序而不是windows应用程序，则来自dll的日志记录可以正常工作。如果我将后端改为" file“而不是"console”，windows应用程序会正确地记录到该文件中。所以问题似乎是windows应用程序没有“控制台”。

解决方案是将标准输出/输入管道重定向到新的控制台。必须为win32应用程序执行此操作，因为默认情况下不会创建控制台。

void RedirectIOToConsole()
{
    int hConHandle;
    long lStdHandle;
    CONSOLE_SCREEN_BUFFER_INFO coninfo;
    FILE *fp;

    // allocate a console for this app
    AllocConsole();

    // set the screen buffer to be big enough to let us scroll text
    GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &coninfo);
    coninfo.dwSize.Y = MAX_CONSOLE_LINES;

    SetConsoleScreenBufferSize(GetStdHandle(STD_OUTPUT_HANDLE), coninfo.dwSize);

    // redirect unbuffered STDOUT to the console
    lStdHandle = (long)GetStdHandle(STD_OUTPUT_HANDLE);
    hConHandle = _open_osfhandle(lStdHandle, _O_TEXT);
    fp = _fdopen( hConHandle, "w" );
    *stdout = *fp;
    setvbuf( stdout, NULL, _IONBF, 0 );

    // redirect unbuffered STDIN to the console
    lStdHandle = (long)GetStdHandle(STD_INPUT_HANDLE);
    hConHandle = _open_osfhandle(lStdHandle, _O_TEXT);
    fp = _fdopen( hConHandle, "r" );
    *stdin = *fp;
    setvbuf( stdin, NULL, _IONBF, 0 );

    // redirect unbuffered STDERR to the console
    lStdHandle = (long)GetStdHandle(STD_ERROR_HANDLE);
    hConHandle = _open_osfhandle(lStdHandle, _O_TEXT);
    fp = _fdopen( hConHandle, "w" );
    *stderr = *fp;
    setvbuf( stderr, NULL, _IONBF, 0 );

    // make cout, wcout, cin, wcin, wcerr, cerr, wclog and clog
    // point to console as well
    std::ios::sync_with_stdio();
}

然后从DllMain调用此函数。

BOOL APIENTRY DllMain( HMODULE hModule,
                   DWORD  ul_reason_for_call,
                   LPVOID lpReserved
                 )
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:
    {
        RedirectIOToConsole();

        int panres =  pantheios::pantheios_init();  

        if(panres < 0)
        {
            fprintf(stderr, "Failed to initialise the Pantheios libraries: %s\n", 
                    pantheios::pantheios_getInitErrorString(panres));

            return FALSE;
        }

        // Set the file name for all back-ends.
        //pantheios_be_file_setFilePath("output.log");
    }
    break;
case DLL_THREAD_ATTACH:
    break;
case DLL_THREAD_DETACH:
    break;
case DLL_PROCESS_DETACH:
    pantheios::pantheios_uninit();
    break;
}
return TRUE;
}

Answer 2

AFAICT，你的代码看起来是完整和正确的，但很难知道你是如何使用它的，从哪里，以及何时你得到了异常。我认为你应该提供更多的信息。

我要说的一件事是:您可能想要使用Pantheios的内部日志"bailout“功能--我想是日志。

fprintf(stderr, "Failed to initialise the Pantheios libraries: %s\n",
    pantheios::pantheios_getInitErrorString(panres));

会更好地写成

pantheios::util::onBailOut(pantheios::emergency,
    "Failed to initialise the Pantheios libraries",
    PANTHEIOS_FE_PROCESS_IDENTITY,
    pantheios::getInitErrorString(panres));

这样，日志初始化失败本身就会被记录下来。