libstdc++: Mark some more algorithms constexpr for C++20

As per P0202.

libstdc++-v3/ChangeLog:

	* include/bits/stl_algo.h (for_each_n): Mark constexpr for C++20.
	(search): Likewise for the overload that takes a searcher.
	* testsuite/25_algorithms/for_each/constexpr.cc: Test constexpr
	std::for_each_n.
	* testsuite/25_algorithms/search/constexpr.cc: Test constexpr
	std::search overload that takes a searcher.

(cherry picked from commit f017952d31ba8fa965106505bed5844cc1a63b4b)

diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h
index 778a14be97f091b463f2af2ff32975eacff92b05..bfab5a06cdaae03283d14c829d7666c94b2c7a7c 100644 (file)
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -3854,6 +3854,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  If `__f` has a return value it is ignored.
   */
   template<typename _InputIterator, typename _Size, typename _Function>
+    _GLIBCXX20_CONSTEXPR
     _InputIterator
     for_each_n(_InputIterator __first, _Size __n, _Function __f)
     {
@@ -4273,6 +4274,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return @p __searcher(__first,__last).first
   */
   template<typename _ForwardIterator, typename _Searcher>
+    _GLIBCXX20_CONSTEXPR
     inline _ForwardIterator
     search(_ForwardIterator __first, _ForwardIterator __last,
           const _Searcher& __searcher)

diff --git a/libstdc++-v3/testsuite/25_algorithms/for_each/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/for_each/constexpr.cc
index 1bece35a0d9dc3cbe7de96cbc02e52720a6dc9d6..b3aca23eccc31c58cd22594ff23f5256b3cc91af 100644 (file)
--- a/libstdc++-v3/testsuite/25_algorithms/for_each/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/for_each/constexpr.cc
@@ -34,3 +34,15 @@ test()
 }
 
 static_assert(test());
+
+constexpr bool
+test_n()
+{
+  int tot = 0;
+  auto sum = [&total = tot](int i){ total += i; };
+  auto sum2 = std::for_each_n(ca0.begin(), std::size(ca0)-1, sum);
+
+  return tot == 55;
+}
+
+static_assert(test_n());

diff --git a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
index ba9437eced7b9b0f42f1a039c3496d9df268dda3..e34194cfc5db474ddfb5578edc16e0c5400d3602 100644 (file)
--- a/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/search/constexpr.cc
@@ -31,6 +31,10 @@ test()
                                 cam.begin(), cam.end(),
                                 std::equal_to<int>());
 
+  const auto outtt2
+    = std::search(ca0.begin(), ca0.end(),
+                 std::default_searcher(cam.begin(), cam.end()));
+
   return true;
 }