On Feb 2 13:14, Corinna Vinschen wrote: > On Feb 2 12:29, Bruno Haible wrote: > > Hello Eric, > > > > > ... POSIX requires that 1 wchar_t corresponds to 1 character > > > ... > > > > What consequences does this have? > > > > > > > > 1) All code that uses the functions from <wctype.h> (wide character > > > > classification and mapping) or wcwidth() malfunctions on strings > > > > that > > > > contains Unicode characters outside the BMP, i.e. outside the range > > > > U+0000..U+FFFF. > > > > > > Not necessarily. Such code falls outside of POSIX, but it may still be > > > a well-behaved extension if given sane behavior for how to deal with > > > surrogates. > > > > No. Code that uses <wctype.h> and wcwidth() is written precisely according > > to POSIX. The problem is that this code cannot work correctly when wchar_t[] > > is in UTF-16 encoding. There simply is no way to define these functions > > in a reasonable way for surrogates. > > > > For example: > > U+1031E = 0xD800 0xDF1E is a letter (iswalpha should be true) > > U+10320 = 0xD800 0xDF20 is not a letter (iswalpha should be false) > > U+1D31E = 0xD834 0xDF1E is not a letter (iswalpha should be false) > > U+1D320 = 0xD834 0xDF20 is not a letter (iswalpha should be false) > > U+1D71E = 0xD835 0xDF1E is a letter (iswalpha should be true) > > U+1D720 = 0xD835 0xDF20 is a letter (iswalpha should be true) > > There is no way that a system can provide this information through a > > function 'iswalpha' that takes a single wchar_t argument. > > iswalpha takes wint_t, not wchar_t. Since sizeof (wint_t) is 4 byte, > the function can return the correct value, provided that the application > converts the UTF-16 surrogate to UTF-32 before calling iswalpha.
And, please note the wording in SUSv4, for instance in http://calimero.vinschen.de/susv4/functions/iswalpha.html The wc argument is a wint_t, the value of which the application shall ^^^^^^ ^^^^^^^^^^^ ensure is a wide-character code corresponding to a valid character in the current locale, or equal to the value of the macro WEOF. If the argument has any other value, the behavior is undefined. I don't see any words in that which would disallow to convert UTF-16 wchar_t surrogates to a wint_t UTF-32 value before calling one of the wctype functions. Just like you have to be careful not to call the ctype functions with a signed char. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
