动态分配的控制台I / O的Visual Studio 2015问题

Question

I have recently upgraded a project to VS2015. The application is a Windows executable based on some platform independent libraries which are using stdout, stderr. These are redirected by the application to separate pipes used in separate threads which forward the messages to the debugger, syslog, file or to the console (which is dynamically allocated on Windows) according to user options.

The problem is that the new CRT in VC2015 does not support stdio redirection the usual way:

FILE *fp = _fdopen(new_stdout_handle, "w");
*stdout = *fp;
setvbuf(stdout, NULL, _IONBF, 0);

Examining CRT source, the only way to redirect stdout indeed is freopen, which is good to redirect stdout to file or to CONOUT$ but not to pipe. _dup2 is also not a solution because the internal file handle of stdout and stderr are both set to -2 in Windows executables. So, it seems there is no way to redirect stdout, stderr to pipe any more.

Does anybody has a clue, how to redirect stdout, stderr to pipe? Any comment is appreciated.

Answer 1

I have had this issue after moving to VS 2015. The solution is to use the WriteFile() function. This redirects output to stdout. Replace the code all around _open_osfhandle() and _fdopen() with WriteFile(). Here an example

HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
if (hStdout != INVALID_HANDLE_VALUE)
{
   DWORD dwWritten;
   char buf[32];
   sprintf(buf, " WOW! I have been redirected to stdout!");
   long len = (long)strlen(buf);
   BOOL bSuccess = WriteFile(hStdout, buf, len, &dwWritten, NULL);
  //if bSuccess = 1, then you succeeded!
}