Re: ctype_members.cc Comparison Always True

[Martin Sebor]

On 08/03/2015 12:35 PM, Joel Sherrill wrote:

Hi

Just noticed this building the head for arm-rtems4.11. Should
the first comparison be eliminated and, maybe, a comment added?

ctype_members.cc:216:14: warning: comparison of unsigned expression >= 0
is always true [-Wtype-limits]
      if (__wc >= 0 && __wc < 128 && _M_narrow_ok)
               ^
ctype_members.cc: In member function 'virtual const wchar_t*
std::ctype<wchar_t>::do_narrow(const wchar_t*, const wchar_t*, char,
char*) const':
ctype_members.cc:230:14: warning: comparison of unsigned expression >= 0
is always true [-Wtype-limits]
     if (*__lo >= 0 && *__lo < 128)

Unconditionally removing the test alone wouldn't be right for targets
where wchar_t is a signed type. But casting the result to an unsigned
type with as much precision as wchar_t should make it possible to
remove it safely.

Martin