On Wed, 04 Feb 2026 at 13:44 +0000, Jonathan Wakely wrote:
On Sun, 27 Jul 2025 at 21:27 +0100, Caolán McNamara wrote:
From: Caolán McNamara <[email protected]>
libstdc++-v3/ChangeLog:
* include/bits/regex.tcc (__collatenames): Make array const.
Thanks for the patch. This arrived while I was (mostly) offline for a
month in the summer and I missed it.
The change is good, and I think it's safe to push now. I'll take care
of it.
Signed-off-by: Caolán McNamara <[email protected]>
---
libstdc++-v3/include/bits/regex.tcc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/bits/regex.tcc
b/libstdc++-v3/include/bits/regex.tcc
index b94fe4490f7..84c15597436 100644
--- a/libstdc++-v3/include/bits/regex.tcc
+++ b/libstdc++-v3/include/bits/regex.tcc
@@ -125,7 +125,7 @@ namespace __detail
typedef std::ctype<char_type> __ctype_type;
const __ctype_type& __fctyp(use_facet<__ctype_type>(_M_locale));
- static const char* __collatenames[] =
+ static const char* const __collatenames[] =
{
"NUL",
"SOH",
--
2.49.0
I've pushed this to trunk now, thanks again.
For GCC 17 I think we should refactor that function so that we don't
repeat that static array for every instantiation of regex_traits<C>,
something like this:
template<typename _Ch_type>
template<typename _Fwd_iter>
typename regex_traits<_Ch_type>::string_type
regex_traits<_Ch_type>::
lookup_collatename(_Fwd_iter __first, _Fwd_iter __last) const
{
// TODO Add digraph support:
// http://boost.sourceforge.net/libs/regex/doc/collating_names.html
if constexpr (is_same<_CharT, char>::value)
{
string __s(__first, __last);
__detail::__lookup_collatename(__s);
return __s;
}
else
{
typedef std::ctype<char_type> __ctype_type;
const __ctype_type& __fctyp(use_facet<__ctype_type>(_M_locale));
string __s;
for (; __first != __last; ++__first)
__s += __fctyp.narrow(*__first, 0);
__detail::__lookup_collatename(__s);
if (!__s.empty())
return string_type(1, __fctyp.widen(__s[0]));
}
return string_type();
}
Where __detail::__lookup_collatename is a non-template function like
this:
inline void
__lookup_collatename(string& __name)
{
static const char* const __collatenames[] =
{
"NUL",
"SOH",
...
"tilde",
"DEL",
};
for (const auto& __it : __collatenames)
if (__s == __it)
{
__s.assign(1, static_cast<char>(&__it - __collatenames));
return;
}
__s.clear();
}
This way we only call narrow/widen when we don't already have a string
of char, and we only emit that array of strings into the binary once.
