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Re: wchar_t: signed or unsigned?

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On 22-Apr-14 05:21, Malcolm McLean wrote:
> On Monday, April 21, 2014 5:55:52 PM UTC+1, DSF wrote:
>> Hello, group!
>> 
>> Is wchar_t signed or unsigned?  Is it different in C++ than in C?
>> Or is it one of those things left up to the compiler writer?
>> 
>> I need to know because I'm dealing with an array of chars, but
>> they are treated by the outside world as ints.  EOFs and error
>> codes are expressed in negative values.  So I am using unsigned
>> chars for the array to avoid the possibility of one of the array
>> members being > 127 and being sign extended to a negative int.
>> 
>> I also have an array of wchar_t for dealing with Windows 16-bit 
>> Unicode.  I don't know if Unicode utilizes the fifteenth bit, but
>> I don't want to take any chances.  In my compiler, wchar_t is
>> defined as "unsigned short" so I don't expect any problems.  But
>> I'd like to know the official word on it.  I did Google the
>> question, but found page after page espousing which form of Unicode
>> is best.  Interesting reading, but not an answer.
> 
> It depends how portable you need to be.

Please don't encourage sloppy coding.

> 16 bits aren't enough to encode all the glyphs in every language in
> the world, so if you must support all of Unicode, you can't use
> Windows wchar_t at all. However the higher Unicode numbers are used
> for pretty marginal alphabets, 15 bits is enough for most purposes.

OTOH, there are many CJK ideographs outside the BMP, and the Chinese
govt specifically tests for handling of such characters; fail that test
and you can't legally import your software into one of the largest and
fastest growing markets in the world.

There are several other ranges outside the BMP as well:

10000 — 1007F  	Linear B Syllabary
10080 — 100FF  	Linear B Ideograms
10100 — 1013F  	Aegean Numbers
10300 — 1032F  	Old Italic
10330 — 1034F  	Gothic
10380 — 1039F  	Ugaritic
10400 — 1044F  	Deseret
10450 — 1047F  	Shavian
10480 — 104AF  	Osmanya
10800 — 1083F  	Cypriot Syllabary
1D000 — 1D0FF  	Byzantine Musical Symbols
1D100 — 1D1FF  	Musical Symbols
1D300 — 1D35F  	Tai Xuan Jing Symbols
1D400 — 1D7FF  	Mathematical Alphanumeric Symbols
20000 — 2A6DF  	CJK Unified Ideographs Extension B
2F800 — 2FA1F  	CJK Compatibility Ideographs Supplement
E0000 — E007F  	Tags

And more are added with each release of the Unicode Standard.

> Unicode defines a series of so-called "non-character code points" of
> which 0xFFFF is one, You can use these internally, but you can't export
> unicode sequences containing these reserved code points. I don't know
> if any Windows fonts actually use Unicode characters 0x7FFFF to 0xFFFFF.
> Obviously you won't be able to support them if you use bit 15 as an
> internal flag.

If you appropriate bit 15, you can't use the entire upper half of the
BMP (8000-FFFF), as well as the other planes (10000-10FFFF):

A000 — A48F  	Yi Syllables
A490 — A4CF  	Yi Radicals
AC00 — D7AF  	Hangul Syllables
D800 — DB7F  	High Surrogates
DB80 — DBFF  	High Private Use Surrogates
DC00 — DFFF  	Low Surrogates
E000 — F8FF  	Private Use Area
F900 — FAFF  	CJK Compatibility Ideographs
FB00 — FB4F  	Alphabetic Presentation Forms
FB50 — FDFF  	Arabic Presentation Forms-A
FE00 — FE0F  	Variation Selectors
FE20 — FE2F  	Combining Half Marks
FE30 — FE4F  	CJK Compatibility Forms
FE50 — FE6F  	Small Form Variants
FE70 — FEFF  	Arabic Presentation Forms-B
FF00 — FFEF  	Halfwidth and Fullwidth Forms
FFF0 — FFFF  	Specials

S

-- 
Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking

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Thread

wchar_t: signed or unsigned? DSF <notavalid@address.here> - 2014-04-21 12:55 -0400
  Re: wchar_t: signed or unsigned? Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2014-04-21 20:02 +0200
  Re: wchar_t: signed or unsigned? Seungbeom Kim <musiphil@bawi.org> - 2014-04-21 11:07 -0700
    Re: wchar_t: signed or unsigned? Keith Thompson <kst-u@mib.org> - 2014-04-21 11:24 -0700
      Re: wchar_t: signed or unsigned? Seungbeom Kim <musiphil@bawi.org> - 2014-04-21 11:57 -0700
        Re: wchar_t: signed or unsigned? James Kuyper <jameskuyper@verizon.net> - 2014-04-21 15:13 -0400
  Re: wchar_t: signed or unsigned? James Kuyper <jameskuyper@verizon.net> - 2014-04-21 14:31 -0400
  Re: wchar_t: signed or unsigned? Stephen Sprunk <stephen@sprunk.org> - 2014-04-21 15:28 -0500
    Re: wchar_t: signed or unsigned? James Kuyper <jameskuyper@verizon.net> - 2014-04-21 16:48 -0400
      Re: wchar_t: signed or unsigned? Keith Thompson <kst-u@mib.org> - 2014-04-21 14:08 -0700
  Re: wchar_t: signed or unsigned? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-22 03:21 -0700
    Re: wchar_t: signed or unsigned? Stephen Sprunk <stephen@sprunk.org> - 2014-04-22 10:48 -0500
    Re: wchar_t: signed or unsigned? Keith Thompson <kst-u@mib.org> - 2014-04-22 09:10 -0700
  Re: wchar_t: signed or unsigned? gordonb.8ql82@burditt.org (Gordon Burditt) - 2014-04-23 03:31 -0500
    Re: wchar_t: signed or unsigned? Stephen Sprunk <stephen@sprunk.org> - 2014-04-25 10:00 -0500
      Re: wchar_t: signed or unsigned? Keith Thompson <kst-u@mib.org> - 2014-04-25 09:00 -0700
        Re: wchar_t: signed or unsigned? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-25 10:27 -0700
        Re: wchar_t: signed or unsigned? Stephen Sprunk <stephen@sprunk.org> - 2014-04-25 16:43 -0500

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