The Windows SDK defines some string functions that provide special processing for buffer handling, with the goal of reducing security issues that involve buffer overruns. These functions are defined in the <StrSafe.h> header. If you are unfamiliar with them, a quick introduction can be found here.
Some of these functions include a parameter for locale information. These locale-aware StrSafe functions have an _l suffix, for example: StringCbPrintf_l.
However, if you try to use the aforementioned function in your Windows C++ code after including <StrSafe.h>, the compiler will complain with an error message like:
error C3861: ‘StringCbPrintf_l’: identifier not found
After some spelunking in the gigantic <StrSafe.h> header with the help of some search tool, you will discover that these locale-aware functions are excluded by default, and you have to explicitly enable them, #defining the preprocessor macro STRSAFE_LOCALE_FUNCTIONS.
This doesn’t seem mentioned in the MSDN documentation for these functions (at least, I was unable to find a note about that).
I would have preferred a different policy of enabling them by default, and if for some reasons these functions would conflict with some existing code bases, those could be disabled defining a macro like STRSAFE_NO_LOCALE_FUNCTIONS (just like the existing approach of explicitly disabling functions with the STRSAFE_NO_CB_FUNCTIONS and STRSAFE_NO_CCH_FUNCTIONS macros).