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On Dec 18 14:52, Steven Abner wrote: > > On 17 Dec 2013, at 4:58 PM, Corinna Vinschen wrote: > > > On Dec 17 15:53, Craig Howland wrote: > >> > >> On 12/17/2013 04:42 AM, Corinna Vinschen wrote: > >>> On Dec 16 16:54, JF Bastien wrote: > >>>> +#ifndef WCHAR_MAX > >>>> #ifdef __WCHAR_MAX__ > >>>> #define WCHAR_MAX __WCHAR_MAX__ > >>>> +#elif defined(__WCHAR_UNSIGNED__) > >>>> +#define WCHAR_MAX 0xffffffffu > >>>> +#else > >>>> +#define WCHAR_MAX 0x7fffffffu > >>>> #endif > >>> and this is not quite ok. You're assuming that wchar_t is 4 bytes, but it > >>> isn't on all platforms. The fallbacks should take that into account, > >>> along the lines of > >>> > >>> #define WCHAR_MAX ((wchar_t)-1) > >>> > >>> > >> Unfortunately, this is not OK in general, as *_MAX defines are > >> required to be able to be used in preprocessor expressions, and > >> casts are not always allowed in them. > > > > Then it has to be done differently. The point is, you can't just set > > WCHAR_MAX to 0xffffffffu or 0x7fffffffu because it's wrong for some > > platforms. If the compiler doesn't provide the information, there has > > to be another way. > > Hi > I have a question. The original post was about compiling newlib as the > C library. I thought newlib supports UTF32 encodings? If so then why > can't newlib use 0xffffffff? I can see how an embedded system could > redefine to 0xff if they only use ASCII. So if the original question one > that the person compiled using LLVM's libc++ without an architecture > defining wchar_t ? Not the C lib defines the size of wchar_t, the underlying system and the compiler does. On Windows-based systems like Cygwin, for instance, wchar_t is 2 bytes since that matches the UTF-16 UNICODE representation of the underlying Windows. Cygwin's gcc returns: #define __WCHAR_MAX__ 65535 #define __WCHAR_MIN__ 0 #define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 2 #define __WCHAR_TYPE__ short unsigned int #define __SIZEOF_WCHAR_T__ 2 and the system designed of arbitrary embedded targets might do the same. Corinna -- Corinna Vinschen Cygwin Maintainer Red Hat
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