So that mean __STDC_ISO_10646__ defined may not be UCS4 but UCS2 or UTF-16, right?
Nelson H. F. Beebe wrote on 3/3/2004, 1:49 PM: > "Frank Yung-Fong Tang" <[EMAIL PROTECTED]> asks on Wed, 3 Mar 2004 > 12:38:49 > -0500: > > >> Does it also mean wchar_t is 4 bytes if __STDC_ISO_10646__ is > defined? > >> or does it only mean wchar_t hold the character in ISO_10646 > >> (which mean it could be 2 bytes, 4 bytes or more than that?) > > Here is the exact text from > > INTERNATIONAL ISO/IEC STANDARD 9899 > Second edition > 1999-12-01 > Programming languages -- C > > >> ... > >> __STDC_ISO_10646__ An integer constant of the form yyyymmL (for > >> example, 199712L), intended to indicate > >> that values of type wchar_t are the coded > >> representations of the characters defined > >> by ISO/IEC 10646, along with all amendments > >> and technical corrigenda as of the > >> specified year and month. > >> ... > > It says nothing more about the size of wchar_t, or what encodings are > used: note the vague language "coded representations...". This means > effectively that the implementation, not the Standard, decides. > > Very few current Unix C or C++ compilers even define the symbol > __STDC_ISO_10646__; the C/C++ feature test package at > > ftp://ftp.math.utah.edu/pub/features > http://www.math.utah.edu/pub/features > > probes that macro value, and many others. > > My logs of its runs in about 90 build environments show definitions > with values 200009 for GNU gcc versions 3.x (all platforms), Intel icc > versions 7.x and 8.0 (Intel IA-32 and IA-64), and Portland Group pgcc > versions 4.x and 5.x (Intel IA-32). On all of these, it reports that > sizeof(wchar_t) = 4, but of course, that says nothing whatever about > the encoding. > > ------------------------------------------------------------------------------- > > - Nelson H. F. Beebe Tel: +1 801 581 > 5254 - > - University of Utah FAX: +1 801 581 > 4148 - > - Department of Mathematics, 110 LCB Internet e-mail: > [EMAIL PROTECTED] - > - 155 S 1400 E RM 233 [EMAIL PROTECTED] > [EMAIL PROTECTED] - > - Salt Lake City, UT 84112-0090, USA URL: > http://www.math.utah.edu/~beebe - > ------------------------------------------------------------------------------- > >
