[committed] libstdc++: Implement LWG 3422 for std::seed_seq

[Jonathan Wakely <jwakely@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 705 bytes --]

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.

Tested powerpc64le-linux. Committed to trunk.


[-- Attachment #2: patch.txt --]
[-- Type: text/plain, Size: 3088 bytes --]

commit 6c63cb231e4cf99552bb7904ebe402f7adcafda4
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 22 18:05:11 2021

    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.

diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 0da013c5f45..ed0d7a832f1 100644
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -6073,7 +6073,7 @@ _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 1357e181874..8e2b702b0be 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -3231,7 +3231,7 @@ 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 18f55e723f0..62434a66591 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 44b855e5627..1ed9eb784c3 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();