From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Mon, 20 Mar 2023 20:19:24 +0000 (-0600)
Subject: Use a feature test macro to check for std::type_identity.
X-Git-Tag: v9.5.0-rc1~445^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F14915%2Fhead;p=dealii.git

Use a feature test macro to check for std::type_identity.
---

diff --git a/cmake/checks/check_01_cxx_features.cmake b/cmake/checks/check_01_cxx_features.cmake
index b6b9a0b28a..0bd45a0b1d 100644
--- a/cmake/checks/check_01_cxx_features.cmake
+++ b/cmake/checks/check_01_cxx_features.cmake
@@ -81,6 +81,10 @@ macro(_test_cxx20_support)
     #  error \"insufficient support for C++20\"
     #endif
 
+    #if !(defined __cpp_type_identity) || (__cpp_lib_type_identity < 201806)
+    #  error \"insufficient support for C++20\"
+    #endif
+
 
     // Test concepts and requires clauses
     template <int dim, int spacedim>