From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 15 Jan 2024 16:51:39 +0000 (+0000)
Subject: libstdc++: Fix redefinition error in std::tuple [PR108822]
X-Git-Tag: basepoints/gcc-15~2883
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1e88a151f878e0a139bf55eb0cee2506fb903274;p=thirdparty%2Fgcc.git

libstdc++: Fix redefinition error in std::tuple [PR108822]

When using a compiler that doesn't define __cpp_conditional_explicit
there's a redefinition error for tuple::__nothrow_assignable. This is
because it's defined in different places for the pre-C++20 and C++20
implementations, which are controled by different preprocessor
conditions. For certain combinations of C++20 feature test macros it's
possible for both __nothrow_assignable definitions to be in scope.

Move the pre-C++20 __assignable and __nothrow_assignable definitions adjacent to
their use, so that only one set of definitions is visible for any given
set of feature test macros.

libstdc++-v3/ChangeLog:

	PR libstdc++/108822
	* include/std/tuple (__assignable, __is_nothrow_assignable):
	Move pre-C++20 definitions adjacent to their use.
---

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 5f4a393b532c..2f6e419ea5bf 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -1237,20 +1237,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  _TCC<_Cond>::template __is_explicitly_constructible<_Args...>(),
 	  bool>;
 
-      template<typename... _UElements>
-	static constexpr
-	__enable_if_t<sizeof...(_UElements) == sizeof...(_Elements), bool>
-	__assignable()
-	{ return __and_<is_assignable<_Elements&, _UElements>...>::value; }
-
-      // Condition for noexcept-specifier of an assignment operator.
-      template<typename... _UElements>
-	static constexpr bool __nothrow_assignable()
-	{
-	  return
-	    __and_<is_nothrow_assignable<_Elements&, _UElements>...>::value;
-	}
-
       // Condition for noexcept-specifier of a constructor.
       template<typename... _UElements>
 	static constexpr bool __nothrow_constructible()
@@ -1685,7 +1671,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	operator=(_UTuple&& __u) const;
 #endif // C++23
 
-#else // ! concepts
+#else // ! (concepts && consteval)
+
+    private:
+      template<typename... _UElements>
+	static constexpr
+	__enable_if_t<sizeof...(_UElements) == sizeof...(_Elements), bool>
+	__assignable()
+	{ return __and_<is_assignable<_Elements&, _UElements>...>::value; }
+
+      // Condition for noexcept-specifier of an assignment operator.
+      template<typename... _UElements>
+	static constexpr bool __nothrow_assignable()
+	{
+	  return
+	    __and_<is_nothrow_assignable<_Elements&, _UElements>...>::value;
+	}
+
+    public:
 
       _GLIBCXX20_CONSTEXPR
       tuple&
@@ -1728,7 +1731,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  this->_M_assign(std::move(__in));
 	  return *this;
 	}
-#endif // concepts
+#endif // concepts && consteval
 
       // tuple swap
       _GLIBCXX20_CONSTEXPR