From ad0b9cf1a076fb9a802d9ba7fa2223aa3166dca2 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 22 Mar 2023 11:10:38 +0000
Subject: [PATCH] libstdc++: Make std::istream_iterator copy ctor constexpr
(LWG 3600)
As explained in LWG 3600, we never implemented a C++0x change that made
the copy constructor of std::istream_iterator defined as defaulted. That
would be an ABI break, so the resolution of LWG 3600 is to not require
it to be trivial, but just constexpr and conditionally noexcept. This
applies that resolution.
libstdc++-v3/ChangeLog:
* include/bits/stream_iterator.h (istream_iterator): Add
constexpr to copy constructor, as per LWG 3600.
* testsuite/24_iterators/istream_iterator/cons/constexpr.cc:
Check copy construction.
---
libstdc++-v3/include/bits/stream_iterator.h | 1 +
.../24_iterators/istream_iterator/cons/constexpr.cc | 5 +++++
2 files changed, 6 insertions(+)
diff --git a/libstdc++-v3/include/bits/stream_iterator.h b/libstdc++-v3/include/bits/stream_iterator.h
index 298d4406afdd..9dc4a550be60 100644
--- a/libstdc++-v3/include/bits/stream_iterator.h
+++ b/libstdc++-v3/include/bits/stream_iterator.h
@@ -80,6 +80,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _M_stream(std::__addressof(__s)), _M_ok(true)
{ _M_read(); }
+ _GLIBCXX_CONSTEXPR
istream_iterator(const istream_iterator& __obj)
_GLIBCXX_NOEXCEPT_IF(is_nothrow_copy_constructible<_Tp>::value)
: _M_stream(__obj._M_stream), _M_value(__obj._M_value),
diff --git a/libstdc++-v3/testsuite/24_iterators/istream_iterator/cons/constexpr.cc b/libstdc++-v3/testsuite/24_iterators/istream_iterator/cons/constexpr.cc
index 824cd93ecbe3..95fda572d8e1 100644
--- a/libstdc++-v3/testsuite/24_iterators/istream_iterator/cons/constexpr.cc
+++ b/libstdc++-v3/testsuite/24_iterators/istream_iterator/cons/constexpr.cc
@@ -24,5 +24,10 @@ int main()
{
__gnu_test::constexpr_default_constructible test;
test.operator()<std::istream_iterator<char>>();
+
+ // LWG 3600. Making istream_iterator copy constructor trivial is an ABI break
+ __gnu_test::constexpr_single_value_constructible test2;
+ test2.operator()<std::istream_iterator<char>, std::istream_iterator<char>>();
+
return 0;
}
--
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