From a7de766c55577ba7c755b9b5e88201b5bca0d7c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christoph=20Gr=C3=BCninger?= <gruenich@dune-project.org>
Date: Thu, 12 Mar 2020 23:25:07 +0100
Subject: [PATCH] [cmake] Don't check for C++17 features which we require
anyway
Set the following variables always to 1:
DUNE_HAVE_CXX_CLASS_TEMPLATE_ARGUMENT_DEDUCTION
DUNE_HAVE_CXX_OPTIONAL
DUNE_HAVE_CXX_VARIANT
DUNE_SUPPORTS_CXX_THROW_IN_CONSTEXPR
DUNE_HAVE_C_ALIGNED_ALLOC
---
cmake/modules/CheckCXXFeatures.cmake | 102 ---------------------------
config.h.cmake | 26 +++----
2 files changed, 11 insertions(+), 117 deletions(-)
diff --git a/cmake/modules/CheckCXXFeatures.cmake b/cmake/modules/CheckCXXFeatures.cmake
index ba885874d..f0e791bbf 100644
--- a/cmake/modules/CheckCXXFeatures.cmake
+++ b/cmake/modules/CheckCXXFeatures.cmake
@@ -19,15 +19,6 @@
# :code:`HAS_ATTRIBUTE_DEPRECATED_MSG`
# True if attribute deprecated("msg") is supported
#
-# :code:`DUNE_HAVE_CXX_CLASS_TEMPLATE_ARGUMENT_DEDUCTION`
-# True if C++17's class template argument deduction is supported
-#
-# :code:`DUNE_HAVE_CXX_OPTIONAL`
-# True if C++17's optional implementation is supported
-#
-# :code:`DUNE_HAVE_CXX_VARIANT`
-# True if C++17's variant implementation is supported
-#
# .. cmake_variable:: DISABLE_CXX_VERSION_CHECK
#
# You may set this variable to TRUE to disable checking for
@@ -321,67 +312,6 @@ check_cxx_source_compiles("
" HAVE_IS_INDEXABLE_SUPPORT
)
-# support for C++17's class template deduction guides
-check_cxx_source_compiles("
- #include <type_traits>
-
- template<typename T1>
- struct A {
- A(T1) {}
-
- template<typename T2>
- A(T2, T2) {}
- };
-
- struct B {
- using type = bool;
- };
-
- template<typename T2>
- A(T2, T2)
- -> A<typename T2::type>;
-
- int main()
- {
- A a1(1);
- static_assert(std::is_same_v< decltype(a1), A<int> >);
-
- B b;
- A a2(b, b);
- static_assert(std::is_same_v< decltype(a2), A<bool> >);
- }
-" DUNE_HAVE_CXX_CLASS_TEMPLATE_ARGUMENT_DEDUCTION
- )
-
-
-# support for C++17's optional implementation
-check_cxx_source_compiles("
- #include <optional>
- #include <string>
-
- int main()
- {
- std::optional< std::string > a;
- std::string b = a.value_or( \"empty\" );
- }
-" DUNE_HAVE_CXX_OPTIONAL
- )
-
-
-# support for C++17's variant implementation
-check_cxx_source_compiles("
- #include <variant>
- #include <string>
-
- int main()
- {
- std::variant< int, std::string > a;
- a = \"stringvalue\";
- std::string b = std::get< std::string >(a);
- }
-" DUNE_HAVE_CXX_VARIANT
- )
-
# find the threading library
if(NOT DEFINED THREADS_PREFER_PTHREAD_FLAG)
@@ -475,38 +405,6 @@ if(NOT STDTHREAD_WORKS)
endif(NOT STDTHREAD_WORKS)
-# Check whether we can conditionally throw exceptions in constexpr context to
-# signal errors both at compile time and at run time - this does not work in GCC 5
-check_cxx_source_compiles("
- constexpr int foo(int bar)
- {
- if (bar < 0)
- throw bar;
- int r = 1;
- for (int i = 0 ; i < bar ; ++i)
- r += r;
- return r;
- }
-
- int main()
- {
- static_assert(foo(4) == 16, \"test failed\");
- return 0;
- }
-" DUNE_SUPPORTS_CXX_THROW_IN_CONSTEXPR
- )
-
-# Check whether the stadard library supports aligned_alloc()
-check_cxx_source_compiles("
- #include <cstdlib>
- int main()
- {
- int* p = static_cast<int*>(aligned_alloc(64, 64*sizeof *p));
- }
-" DUNE_HAVE_C_ALIGNED_ALLOC
- )
-
-
# ******************************************************************************
#
diff --git a/config.h.cmake b/config.h.cmake
index e5b462560..6abb0aea1 100644
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -29,21 +29,6 @@
/* does the compiler support __attribute__((unused))? */
#cmakedefine HAS_ATTRIBUTE_UNUSED 1
-/* does the compiler support C++17's class template argument deduction? */
-#cmakedefine DUNE_HAVE_CXX_CLASS_TEMPLATE_ARGUMENT_DEDUCTION 1
-
-/* does the compiler support C++17's optional? */
-#cmakedefine DUNE_HAVE_CXX_OPTIONAL 1
-
-/* does the compiler support C++17's variant? */
-#cmakedefine DUNE_HAVE_CXX_VARIANT 1
-
-/* does the compiler support conditionally throwing exceptions in constexpr context? */
-#cmakedefine DUNE_SUPPORTS_CXX_THROW_IN_CONSTEXPR 1
-
-/* does the standard library provides aligned_alloc()? */
-#cmakedefine DUNE_HAVE_C_ALIGNED_ALLOC 1
-
/* does the standard library provide <experimental/type_traits> ? */
#cmakedefine DUNE_HAVE_HEADER_EXPERIMENTAL_TYPE_TRAITS 1
@@ -135,6 +120,17 @@
/* end private */
+
+/* old feature support macros which were tested until 2.7, kept around for one more release */
+/* As these are now always supported due to the new compiler requirements, they are directly */
+/* defined without an explicit test. */
+#define DUNE_HAVE_CXX_CLASS_TEMPLATE_ARGUMENT_DEDUCTION 1
+#define DUNE_HAVE_CXX_OPTIONAL 1
+#define DUNE_HAVE_CXX_VARIANT 1
+#define DUNE_SUPPORTS_CXX_THROW_IN_CONSTEXPR 1
+#define DUNE_HAVE_C_ALIGNED_ALLOC 1
+
+
/* Define to 1 if the compiler properly supports testing for operator[] */
#cmakedefine HAVE_IS_INDEXABLE_SUPPORT 1
--
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