The towupper() function has as a domain a type wint_t,
the value of which the application shall ensure is a
character representable as a wchar_t, and a wide-character code
corresponding to a valid character in the current locale or
the value of WEOF. If the argument has any other value, the behavior
is undefined. If the argument of towupper() represents
a lowercase wide-character code, and there exists a corresponding
uppercase wide-character code (as defined by character type
information in the program locale category LC_CTYPE ), the result
shall be the corresponding uppercase wide-character code.
All other arguments in the domain are returned unchanged.
Upon successful completion, towupper() shall return the uppercase
letter corresponding to the argument passed. Otherwise,
it shall return the argument unchanged.
No errors are defined.
The following sections are informative.
setlocale() , the Base Definitions volume of IEEE Std 1003.1-2001,
Chapter 7, Locale, <wctype.h>, <wchar.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at