libstdc++: Fix std::__uninitialized_default_n for constant evaluation [PR110542]

libstdc++-v3/ChangeLog:

	PR libstdc++/110542
	* include/bits/stl_uninitialized.h (__uninitialized_default_n):
	Do not use std::fill_n during constant evaluation.

(cherry picked from commit 83cae6c4b788544635a71748e1881c150f42efef)

diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h b/libstdc++-v3/include/bits/stl_uninitialized.h
index 7ed69f53f7d8f04963303c7170f3723ab176ab9b..88e003a30335d8f1a4795d053cebc877d23fad6a 100644 (file)
--- a/libstdc++-v3/include/bits/stl_uninitialized.h
+++ b/libstdc++-v3/include/bits/stl_uninitialized.h
@@ -690,6 +690,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline _ForwardIterator
     __uninitialized_default_n(_ForwardIterator __first, _Size __n)
     {
+#ifdef __cpp_lib_is_constant_evaluated
+      if (std::is_constant_evaluated())
+       return __uninitialized_default_n_1<false>::
+                __uninit_default_n(__first, __n);
+#endif
+
       typedef typename iterator_traits<_ForwardIterator>::value_type
        _ValueType;
       // See uninitialized_fill_n for the conditions for using std::fill_n.