std::towupper (3) - Linux Man Pages
Defined in header <cwctype>
std::wint_t towupper( std::wint_t ch );
Converts the given wide character to uppercase, if possible.
If the value of ch is neither representable as a wchar_t nor equal to the value of the macro WEOF, the behavior is undefined.
ch - wide character to be converted
Uppercase version of ch or unmodified ch if no uppercase version is listed in the current C locale.
Only 1:1 character mapping can be performed by this function, e.g. the uppercase form of 'ß' is (with some exceptions) the two-character string "SS", which cannot be obtained by std::towupper.
ISO_30112 specifies which pairs of Unicode characters are included in this mapping.
The latin letter_'ſ'_(U+017F) is the alternative lowercase form of 'S' (U+0053)
// Run this code
toupper(std::locale) (function template)