Why does _tfopen_s() return an error value of 13 or 2?

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in my MFC application, I set a timer and do something at timer, writting something realtime data; the code is:

//MyApplication.cpp  
OnTimer() FILE* pfile = NULL; 
errno_t errRet = _tfopen_s( &pfile, _T("process.txt"), _T("a") ); 
if ( 0!=errRet && NULL == pfile ) 
{ 
TRACE(_T("errRet=%d, pfile=%p, LastErr=%d\n"), errRet, pfile, GetLastError() );
 } 
//end

sometimes(just very low chance to see it), the if condition is FALSE, and trace is :"errRet=13,pfile=0x00000000, LastErr=183" in my application, there is just one thread(UI main thread) operating this file, so no synchronization. please somebody give me some explain about this BUG!!! thanks!

Posted 26-Nov-09 16:04pm

Leonard Liu

Updated 26-Nov-09 16:59pm

Shog⁹

v3

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Shog⁹ · Answer 1 · 2009-11-26T17:11:00

It doesn't matter if nothing else in your app is accessing the file. If anything holds an open handle on the file then your app will fail to open it. A text editor, log viewer, indexing service maybe... It's outside of your control.

There are other reasons why this might be failing as well. For starters, you aren't specifying a location for the file. Either you're setting the CWD explicitly elsewhere, or you're relying on it being a location you can actually write to... Check both of these assumptions.

Christian Graus · Answer 2 · 2009-11-26T16:09:00

Solution 1

Why did you post this three times ? Is this C, or C++ ? If it's C++, why on earth are you using a FILE* and not iostreams ? If it''s C, why is your code file .cpp ? Whatever the underlying issue, there is no reason I can see to use C file handling in C++, except ignorance.

Posted 26-Nov-09 16:09pm

Christian Graus