From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 22 May 2024 15:49:31 +0000 (+0100)
Subject: libstdc++: Optimize __try_use_facet for const types
X-Git-Tag: basepoints/gcc-16~6420
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=952e67c0d131300f263d729a0fe07bc3655dad27;p=thirdparty%2Fgcc.git

libstdc++: Optimize __try_use_facet for const types

LWG 436 confirmed that const-qualified types are valid arguments for
Facet template parameters (but volatile-qualified types are not). Use the
fast path in std::use_facet and std::has_facet for const T as well as T.

libstdc++-v3/ChangeLog:

	* include/bits/locale_classes.tcc (__try_use_facet): Also avoid
	dynamic_cast for const-qualified facet types.
---

diff --git a/libstdc++-v3/include/bits/locale_classes.tcc b/libstdc++-v3/include/bits/locale_classes.tcc
index c79574e58de..d5ef1911057 100644
--- a/libstdc++-v3/include/bits/locale_classes.tcc
+++ b/libstdc++-v3/include/bits/locale_classes.tcc
@@ -110,7 +110,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // We know these standard facets are always installed in every locale
       // so dynamic_cast always succeeds, just use static_cast instead.
 #define _GLIBCXX_STD_FACET(...) \
-      if _GLIBCXX_CONSTEXPR (__is_same(_Facet, __VA_ARGS__)) \
+      if _GLIBCXX_CONSTEXPR (__is_same(const _Facet, const __VA_ARGS__)) \
 	return static_cast<const _Facet*>(__facets[__i])
 
       _GLIBCXX_STD_FACET(ctype<char>);