On targets where wchar_t is unsigned we get warnings during the
libstdc++ build:
ctype_members.cc: In member function ‘virtual char
std::ctype<wchar_t>::do_narrow(wchar_t, char) const’:
ctype_members.cc:224:14: warning: comparison of unsigned expression in ‘>= 0’
is always true [-Wtype-limits]
224 | 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:247:21: warning: comparison of unsigned expression in ‘>= 0’
is always true [-Wtype-limits]
247 | if (*__lo >= 0 && *__lo < 128)
| ~~~~~~^~~~
This introduces a helper function that converts the wchar_t to an
unsigned type and then does the comparison. This means the comparison is
not target-dependent, and there's no more warning.
libstdc++-v3/ChangeLog:
* config/locale/gnu/ctype_members.cc (use_table): New function.
(ctype<wchar_t>::do_narrow): Use use_table.
---
Tested x86_64-linux and aarch64-linux.
libstdc++-v3/config/locale/gnu/ctype_members.cc | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/config/locale/gnu/ctype_members.cc
b/libstdc++-v3/config/locale/gnu/ctype_members.cc
index 183babb6c3f6..b34446a61ee1 100644
--- a/libstdc++-v3/config/locale/gnu/ctype_members.cc
+++ b/libstdc++-v3/config/locale/gnu/ctype_members.cc
@@ -217,11 +217,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __hi;
}
+ // True if c can be looked up in _M_narrow.
+ [[gnu::always_inline]]
+ static inline bool
+ use_table(wchar_t c)
+ {
+ using U = std::make_unsigned<wchar_t>::type;
+ return U(c) < 128;
+ }
+
char
ctype<wchar_t>::
do_narrow(wchar_t __wc, char __dfault) const
{
- if (__wc >= 0 && __wc < 128 && _M_narrow_ok)
+ if (use_table(__wc) && _M_narrow_ok)
return _M_narrow[__wc];
#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2)
__c_locale __old = __uselocale(_M_c_locale_ctype);
@@ -244,7 +253,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (_M_narrow_ok)
while (__lo < __hi)
{
- if (*__lo >= 0 && *__lo < 128)
+ if (use_table(*__lo))
*__dest = _M_narrow[*__lo];
else
{
--
2.52.0
