From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 19 Jan 2024 12:28:30 +0000 (+0000)
Subject: libstdc++: Fix P2255R2 dangling checks for std::tuple in C++17 [PR108822]
X-Git-Tag: basepoints/gcc-15~1847
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=502a3c03e40e8920afb734c077b045f6c5efd087;p=thirdparty%2Fgcc.git

libstdc++: Fix P2255R2 dangling checks for std::tuple in C++17 [PR108822]

I accidentally used && in a fold-expression instead of || which meant
that in C++17 the tuple(UElements&&...) constructor only failed its
debug assertion if all tuple elements were dangling references. Some
missing tests (noted as "TODO") meant this wasn't tested.

This fixes the fold expression and adds the missing tests.

libstdc++-v3/ChangeLog:

	PR libstdc++/108822
	* include/std/tuple (__glibcxx_no_dangling_refs) [C++17]: Fix
	wrong fold-operator.
	* testsuite/20_util/tuple/dangling_ref.cc: Check tuples with one
	element and three elements. Check allocator-extended
	constructors.
---

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 7a045b3e6a13..be92f1eb973d 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -1299,7 +1299,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // Error if construction from U... would create a dangling ref.
 # if __cpp_fold_expressions
 #  define __glibcxx_dangling_refs(U) \
-  (__reference_constructs_from_temporary(_Elements, U) && ...)
+  (__reference_constructs_from_temporary(_Elements, U) || ...)
 # else
 #  define __glibcxx_dangling_refs(U) \
   __or_<__bool_constant<__reference_constructs_from_temporary(_Elements, U) \
diff --git a/libstdc++-v3/testsuite/20_util/tuple/dangling_ref.cc b/libstdc++-v3/testsuite/20_util/tuple/dangling_ref.cc
index 74fdc2423493..b2dcf3594385 100644
--- a/libstdc++-v3/testsuite/20_util/tuple/dangling_ref.cc
+++ b/libstdc++-v3/testsuite/20_util/tuple/dangling_ref.cc
@@ -7,6 +7,7 @@
 
 #if __cplusplus >= 202002L
 // For C++20 and later, constructors are constrained to disallow dangling.
+static_assert(!std::is_constructible_v<std::tuple<const int&>, long>);
 static_assert(!std::is_constructible_v<std::tuple<const int&, int>, long, int>);
 static_assert(!std::is_constructible_v<std::tuple<int, const int&>, int, long>);
 static_assert(!std::is_constructible_v<std::tuple<const int&, int>,
@@ -30,76 +31,137 @@ static_assert(!std::is_constructible_v<std::tuple<int, const int&>,
 void
 test_ary_ctors()
 {
-  std::tuple<const int&, int> t1(1L, 2);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 33 }
-  // { dg-error "use of deleted function" "" { target c++20 } 33 }
+  std::tuple<const int&> t1(1L);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 34 }
+  // { dg-error "use of deleted function" "" { target c++20 } 34 }
 
-  std::tuple<int, const int&> t2(1, 2L);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 37 }
-  // { dg-error "use of deleted function" "" { target c++20 } 37 }
+  std::tuple<const int&, int> t2(1L, 2);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 38 }
+  // { dg-error "use of deleted function" "" { target c++20 } 38 }
 
-  std::tuple<const int&, const int&> t3(1L, 2L);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 41 }
-  // { dg-error "use of deleted function" "" { target c++20 } 41 }
+  std::tuple<int, const int&> t3(1, 2L);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 42 }
+  // { dg-error "use of deleted function" "" { target c++20 } 42 }
 
-  std::tuple<const int&, const int&> t4(std::pair<long, int>{});
-  // { dg-error "here" "" { target { c++17_down && hosted } } 45 }
-  // { dg-error "use of deleted function" "" { target c++20 } 45 }
+  std::tuple<const int&, const int&> t4(1L, 2L);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 46 }
+  // { dg-error "use of deleted function" "" { target c++20 } 46 }
 
-  std::pair<int, long> p;
-  std::tuple<const int&, const int&> t5(p);
+  std::tuple<const int&, const int&> t5(std::pair<long, int>{});
   // { dg-error "here" "" { target { c++17_down && hosted } } 50 }
   // { dg-error "use of deleted function" "" { target c++20 } 50 }
+
+  std::pair<int, long> p;
+  std::tuple<const int&, const int&> t6(p);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 55 }
+  // { dg-error "use of deleted function" "" { target c++20 } 55 }
+
+  std::tuple<const int&, int, int> t7(1L, 2, 3);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 59 }
+  // { dg-error "use of deleted function" "" { target c++20 } 59 }
 }
 
 void
 test_converting_ctors()
 {
-  std::tuple<long, long> t0;
+  std::tuple<long> t10;
+
+  std::tuple<const int&> t11(t10);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 69 }
+  // { dg-error "use of deleted function" "" { target c++20 } 69 }
+
+  std::tuple<const int&> t12(std::move(t10));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 73 }
+  // { dg-error "use of deleted function" "" { target c++20 } 73 }
 
-  std::tuple<const int&, int> t1(t0);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 60 }
-  // { dg-error "use of deleted function" "" { target c++20 } 60 }
+  std::tuple<long, long> t20;
 
-  std::tuple<int, const int&> t2(t0);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 64 }
-  // { dg-error "use of deleted function" "" { target c++20 } 64 }
+  std::tuple<const int&, int> t21(t20);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 79 }
+  // { dg-error "use of deleted function" "" { target c++20 } 79 }
 
-  std::tuple<const int&, const int&> t3(t0);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 68 }
-  // { dg-error "use of deleted function" "" { target c++20 } 68 }
+  std::tuple<int, const int&> t22(t20);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 83 }
+  // { dg-error "use of deleted function" "" { target c++20 } 83 }
 
-  std::tuple<const int&, int> t4(std::move(t0));
-  // { dg-error "here" "" { target { c++17_down && hosted } } 72 }
-  // { dg-error "use of deleted function" "" { target c++20 } 72 }
+  std::tuple<const int&, const int&> t23(t20);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 87 }
+  // { dg-error "use of deleted function" "" { target c++20 } 87 }
 
-  std::tuple<int, const int&> t5(std::move(t0));
-  // { dg-error "here" "" { target { c++17_down && hosted } } 76 }
-  // { dg-error "use of deleted function" "" { target c++20 } 76 }
+  std::tuple<const int&, int> t24(std::move(t20));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 91 }
+  // { dg-error "use of deleted function" "" { target c++20 } 91 }
 
-  std::tuple<const int&, const int&> t6(std::move(t0));
-  // { dg-error "here" "" { target { c++17_down && hosted } } 80 }
-  // { dg-error "use of deleted function" "" { target c++20 } 80 }
+  std::tuple<int, const int&> t25(std::move(t20));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 95 }
+  // { dg-error "use of deleted function" "" { target c++20 } 95 }
+
+  std::tuple<const int&, const int&> t26(std::move(t20));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 99 }
+  // { dg-error "use of deleted function" "" { target c++20 } 99 }
 
   std::pair<long, long> p0;
-  std::tuple<const int&, int> t7(p0);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 85 }
-  // { dg-error "use of deleted function" "" { target c++20 } 85 }
+  std::tuple<const int&, int> t27(p0);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 104 }
+  // { dg-error "use of deleted function" "" { target c++20 } 104 }
 
-  std::tuple<int, const int&> t8(p0);
-  // { dg-error "here" "" { target { c++17_down && hosted } } 89 }
-  // { dg-error "use of deleted function" "" { target c++20 } 89 }
+  std::tuple<int, const int&> t28(p0);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 108 }
+  // { dg-error "use of deleted function" "" { target c++20 } 108 }
 
-  std::tuple<const int&, int> t9(std::move(p0));
-  // { dg-error "here" "" { target { c++17_down && hosted } } 93 }
-  // { dg-error "use of deleted function" "" { target c++20 } 93 }
+  std::tuple<const int&, int> t29(std::move(p0));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 112 }
+  // { dg-error "use of deleted function" "" { target c++20 } 112 }
 
-  std::tuple<int, const int&> t10(std::move(p0));
-  // { dg-error "here" "" { target { c++17_down && hosted } } 97 }
-  // { dg-error "use of deleted function" "" { target c++20 } 97 }
+  std::tuple<int, const int&> t210(std::move(p0));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 116 }
+  // { dg-error "use of deleted function" "" { target c++20 } 116 }
 }
 
-// TODO: test allocator-extended ctors
-// TODO: test 1-tuple or 3-tuple, not just 2-tuple
+#include <memory>
+
+void
+test_allocator_extended_ctors()
+{
+  std::allocator<int> a;
+
+  std::tuple<const int&> t1(std::allocator_arg, a, 1L);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 128 }
+  // { dg-error "use of deleted function" "" { target c++20 } 128 }
+
+  std::tuple<const int&, int> t2(std::allocator_arg, a, 1L, 2);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 132 }
+  // { dg-error "use of deleted function" "" { target c++20 } 132 }
+
+  std::tuple<long> tl;
+
+  std::tuple<const int&> t3(std::allocator_arg, a, tl);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 138 }
+  // { dg-error "use of deleted function" "" { target c++20 } 138 }
+
+  std::tuple<const int&> t4(std::allocator_arg, a, std::move(tl));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 142 }
+  // { dg-error "use of deleted function" "" { target c++20 } 142 }
+
+  std::tuple<long, long> tll;
+
+  std::tuple<const int&, int> t5(std::allocator_arg, a, tll);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 148 }
+  // { dg-error "use of deleted function" "" { target c++20 } 148 }
+
+  std::tuple<const int&, int> t6(std::allocator_arg, a, std::move(tll));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 152 }
+  // { dg-error "use of deleted function" "" { target c++20 } 152 }
+
+  std::pair<long, long> pll;
+
+  std::tuple<const int&, int> t7(std::allocator_arg, a, pll);
+  // { dg-error "here" "" { target { c++17_down && hosted } } 158 }
+  // { dg-error "use of deleted function" "" { target c++20 } 158 }
+
+  std::tuple<const int&, int> t8(std::allocator_arg, a, std::move(pll));
+  // { dg-error "here" "" { target { c++17_down && hosted } } 162 }
+  // { dg-error "use of deleted function" "" { target c++20 } 162 }
+}
 
 // { dg-error "static assert.* dangling reference" "" { target { c++17_down && hosted } } 0 }