Why can't I write to MFC GUI console?
Posted on 1997-04-22
I've developed a C++ Delaunay/Voronoi triangulation library which runs fine on several flavors of Unix as well as in NT
and Win95 console applications. The debug version of the library writes error and diagnastic information to STDOUT and STDERR as formatted text through cout and cerr.
Now I have an MFC GUI application to visualize the triangulations. I want to be able to allocate a console and have the diagnostic output from the triangulation library go to the console window without having to modify the library (so it still runs on Unix).
The application is a standard MFC app created with AppWizard. I can create the console window using AllocConsole() ( in InitInstance() in the App ), but nothing gets written to it.
I tried to redirect STD_OUTPUT_HANDLE and STD_ERROR_HANDLE using SetStdHandle() but can't seem to get a handle to the newly created console's standard output and standard error. The docs for CreateFile() say to use CON and CONOUT&. What the hell are they? I grepped and searched for these but turned up nothing. What's going on here?
I noticed that before I created the console, GetStdHandle() returned 0 (no console) and after the call to AllocConsole() STD_OUTPUT_HANDLE was 7 (0x00000007). Is this a valid handle? (Doesn't work if it is!)
The docs for AllocConsole() say that the call sets up
(redirects) the std io handles. Why doesn't it work?
I include iostream.h header in the library so that it works with Unix and in console applications. When I build the MFC application I have to use the /NODEFAULTLIB switch to get it to link properly. I also noticed that when I run it from the build menu in devstudio, there are 2 io libraries loaded and one is relocated in memory (forget the exact message). Could this be the problem?
What am I doing wrong? Am I going about this all wrong? Should I be using CreateProsess() instead?
Any help would be appreciated.