[committed] libstdc++: Prevent unwanted ADL in std::to_array [PR111512]
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Commit Message
Tested x86_64-linux. Pushed to trunk.
-- >8 --
As noted in PR c++/111512, GCC does ADL for __builtin_memcpy if it is
unqualified, which can cause errors for template argument types which
cannot be completed.
Casting the memcpy arguments to void* prevents ADL from considering the
problem type.
libstdc++-v3/ChangeLog:
PR libstdc++/111511
PR c++/111512
* include/std/array (to_array): Cast memcpy arguments to void*.
* testsuite/23_containers/array/creation/111512.cc: New test.
---
libstdc++-v3/include/std/array | 4 ++--
.../23_containers/array/creation/111512.cc | 24 +++++++++++++++++++
2 files changed, 26 insertions(+), 2 deletions(-)
create mode 100644 libstdc++-v3/testsuite/23_containers/array/creation/111512.cc
@@ -432,7 +432,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
array<remove_cv_t<_Tp>, _Nm> __arr;
if (!__is_constant_evaluated() && _Nm != 0)
- __builtin_memcpy(__arr.data(), __a, sizeof(__a));
+ __builtin_memcpy((void*)__arr.data(), (void*)__a, sizeof(__a));
else
for (size_t __i = 0; __i < _Nm; ++__i)
__arr._M_elems[__i] = __a[__i];
@@ -461,7 +461,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
array<remove_cv_t<_Tp>, _Nm> __arr;
if (!__is_constant_evaluated() && _Nm != 0)
- __builtin_memcpy(__arr.data(), __a, sizeof(__a));
+ __builtin_memcpy((void*)__arr.data(), (void*)__a, sizeof(__a));
else
for (size_t __i = 0; __i < _Nm; ++__i)
__arr._M_elems[__i] = __a[__i];
new file mode 100644
@@ -0,0 +1,24 @@
+// { dg-do compile { target c++20 } }
+
+// Bug libstdc++/111511 - Incorrect ADL in std::to_array in GCC 11/12/13
+// Bug c++/111512 - GCC's __builtin_memcpy can trigger ADL
+
+#include <array>
+#include <utility>
+
+struct incomplete;
+
+template<class T>
+struct holder {
+ T t; // { dg-bogus "'holder<T>::t' has incomplete type" }
+};
+
+// A complete type that cannot be used as an associated type for ADL.
+using adl_bomb = holder<incomplete>*;
+
+int main()
+{
+ adl_bomb a[1]{};
+ (void) std::to_array(a);
+ (void) std::to_array(std::move(a));
+}