Re: [PATCH] Update newlib so that it passes libc++'s tests

[Craig Howland <howland at LGSInnovations dot com>]

On 12/18/2013 04:53 PM, JF Bastien wrote:
> Thanks for pointing this out, I wasn't aware of this latest glibc fix.
> Here's an updated definition (for both stdint.h and wchar.h). If it
> looks good I'll update the patch, assuming the rest of the ongoing
> discussion doesn't change this snippet further. To summarize other
> discussions, the code first relies on the compiler's own defines
> (__WCHAR_{MIN,MAX}__) and stdint.h/wchar.h includes (which could
> define WCHAR_{MIN,MAX}) to do the right thing. If that fails then
> AFAICT we're stuck with making an educated guess as to what the
> "right" value is, and in some cases that guess will necessarily be
> wrong because we can't use casts. Newlib's current guess (before my
> patch) is 32-bits, so I decided to stick to that and I don't think
> going with 16-bits is any better (it's also wrong in some cases, but
> now it's also different from what previous newlib versions used to
> guess!).
>
> I'm of course open to suggestions here, but I'm not seeing a better
> solution and hope someone else sees one.
There is a better way than guessing, but it is ugly:  add a configure-time check 
that determines what the value is and puts it into the generated newlib.h (in a 
manner analogous to how _LDBL_EQ_DBL is, for example).
> #ifndef WCHAR_MIN
> #ifdef __WCHAR_MIN__
> #define WCHAR_MIN __WCHAR_MIN__
> #elif defined(__WCHAR_UNSIGNED__) || (L'\0' - 1 > 0)
> #define WCHAR_MIN (0 + L'\0')
> #else
> #define WCHAR_MIN (-0x7fffffff - 1 + L'\0')
> #endif
> #endif
>
> #ifndef WCHAR_MAX
> #ifdef __WCHAR_MAX__
> #define WCHAR_MAX __WCHAR_MAX__
> #elif defined(__WCHAR_UNSIGNED__) || (L'\0' - 1 > 0)
> #define WCHAR_MAX (0xffffffffu + L'\0')
> #else
> #define WCHAR_MAX (0x7fffffffu + L'\0')
> #endif
The present wchar.h is broken in this manner already for WCHAR_MAX, so it might 
not be unreasonable to do this for wchar.h now and follow up with a fix for the 
existing MAX issue.  It probably is not good, however, to add the breakage to 
stdint.h.