Microsoft _stprintf warning

Question

Why I get the following warning for the following code :)

Code:

_stprintf(m_szFileNamePath,_T("%s"),strFileName);

warning C4996: '_swprintf': swprintf has been changed to conform with the ISO C standard, adding an extra character count parameter. To use traditional Microsoft swprintf, set _CRT_NON_CONFORMING_SWPRINTFS.

I know _strprintf is a macro which if _UNICODE is defined will evaluate to _swprintf else it will be sprintf.

Now what is this _swprintf. There is a function swprintf, but why is _stprintf evaluating to _swprintf instead of swprintf.

What is the difference b/w the _xxx and xxx functions?

EDIT:

Okay there are two definitions for the UNICODE version of _stprintf, which one is included?

The one in tchar.h or strsafe.h?

Answer 1

http://msdn.microsoft.com/en-us/library/ybk95axf%28VS.80%29.aspx

swprintf is a wide-character version of sprintf; the pointer arguments to swprintf are wide-character strings. Detection of encoding errors in swprintf may differ from that in sprintf. swprintf and fwprintf behave identically except that swprintf writes output to a string rather than to a destination of type FILE, and swprintf requires the count parameter to specify the maximum number of characters to be written. The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current thread locale.

In Visual C++ 2005, swprintf conforms to the ISO C Standard, which requires the second parameter, count, of type size_t. To force the old nonstandard behavior, define _CRT_NON_CONFORMING_SWPRINTFS. In a future version, the old behavior may be removed, so code should be changed to use the new conformant behavior.

Answer 2

Microsoft provides its own extension of CRT _swprintf - is not compatible (for example) with unix

Answer 3

Microsoft (used to?) prefix otherwise widely available non-win32 functions that were not part of the C standard with underscore.

Answer 4

_stprintf(m_szFileNamePath,256,_T("%s"),strFileName);