[gcc r10-10212] libstdc++: Implement LWG 3422 for std::seed_seq

[gcc r10-10212] libstdc++: Implement LWG 3422 for std::seed_seq

[Jonathan Wakely]

https://gcc.gnu.org/g:e7274af45795b450268d7769ddae06f774db4dc9

commit r10-10212-ge7274af45795b450268d7769ddae06f774db4dc9
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 22 18:05:11 2021 +0100

    libstdc++: Implement LWG 3422 for std::seed_seq
    
    This ensures that the std::seed_seq initializer-list constructor will
    not be used for list-initialization unless the initializers in the list
    are integers. This allows list-initialization syntax to be used with a
    pair of pointers and for that to use the appropriate constructor.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/random.h (seed_seq): Constrain initializer-list
            constructor.
            * include/bits/random.tcc (seed_seq): Add template parameter.
            * testsuite/26_numerics/random/seed_seq/cons/default.cc: Check
            for noexcept.
            * testsuite/26_numerics/random/seed_seq/cons/initlist.cc: Check
            constraints.
    
    (cherry picked from commit 6c63cb231e4cf99552bb7904ebe402f7adcafda4)

Diff:
---
 libstdc++-v3/include/bits/random.h                                 | 2 +-
 libstdc++-v3/include/bits/random.tcc                               | 2 +-
 libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/default.cc | 4 +++-
 .../testsuite/26_numerics/random/seed_seq/cons/initlist.cc         | 7 +++++++
 4 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 2bcac1b41b1..2bd6bc1e120 100644
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -6071,7 +6071,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : _M_v()
     { }
 
-    template<typename _IntType>
+    template<typename _IntType, typename = _Require<is_integral<_IntType>>>
       seed_seq(std::initializer_list<_IntType> __il);
 
     template<typename _InputIterator>
diff --git a/libstdc++-v3/include/bits/random.tcc b/libstdc++-v3/include/bits/random.tcc
index a921b9bf815..d7503ee7094 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -3197,7 +3197,7 @@ namespace __detail
     }
 
 
-  template<typename _IntType>
+  template<typename _IntType, typename>
     seed_seq::seed_seq(std::initializer_list<_IntType> __il)
     {
       for (auto __iter = __il.begin(); __iter != __il.end(); ++__iter)
diff --git a/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/default.cc b/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/default.cc
index 73a4390da26..3c4e38a7408 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/default.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/default.cc
@@ -25,6 +25,9 @@
 #include <random>
 #include <testsuite_hooks.h>
 
+static_assert( std::is_nothrow_default_constructible<std::seed_seq>::value,
+	       "LWG 3422" );
+
 void
 test01()
 {
@@ -34,7 +37,6 @@ test01()
   seq.generate(foo.begin(), foo.end());
 
   VERIFY( seq.size() == 0 );
-  //VERIFY();
 }
 
 int
diff --git a/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/initlist.cc b/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/initlist.cc
index 1e2a88d32ff..396141e9c4e 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/initlist.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/seed_seq/cons/initlist.cc
@@ -36,6 +36,13 @@ test01()
   VERIFY( seq.size() == 10 );
 }
 
+void
+lwg3422()
+{
+  int i[32] = { };
+  std::seed_seq ss{i, i+32}; // LWG 3422
+}
+
 int main()
 {
   test01();