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1# C++14 feature support detection
2
3include(CheckCXXSourceCompiles)
4include(CheckCXXCompilerFlag)
5
6if (NOT CMAKE_CXX_STANDARD)
7  set(CMAKE_CXX_STANDARD 11)
8endif()
9message(STATUS "CXX_STANDARD: ${CMAKE_CXX_STANDARD}")
10
11if (CMAKE_CXX_STANDARD EQUAL 20)
12  check_cxx_compiler_flag(-std=c++20 has_std_20_flag)
13  check_cxx_compiler_flag(-std=c++2a has_std_2a_flag)
14
15  if (has_std_20_flag)
16    set(CXX_STANDARD_FLAG -std=c++20)
17  elseif (has_std_2a_flag)
18    set(CXX_STANDARD_FLAG -std=c++2a)
19  endif ()
20elseif (CMAKE_CXX_STANDARD EQUAL 17)
21  check_cxx_compiler_flag(-std=c++17 has_std_17_flag)
22  check_cxx_compiler_flag(-std=c++1z has_std_1z_flag)
23
24  if (has_std_17_flag)
25    set(CXX_STANDARD_FLAG -std=c++17)
26  elseif (has_std_1z_flag)
27    set(CXX_STANDARD_FLAG -std=c++1z)
28  endif ()
29elseif (CMAKE_CXX_STANDARD EQUAL 14)
30  check_cxx_compiler_flag(-std=c++14 has_std_14_flag)
31  check_cxx_compiler_flag(-std=c++1y has_std_1y_flag)
32
33  if (has_std_14_flag)
34    set(CXX_STANDARD_FLAG -std=c++14)
35  elseif (has_std_1y_flag)
36    set(CXX_STANDARD_FLAG -std=c++1y)
37  endif ()
38elseif (CMAKE_CXX_STANDARD EQUAL 11)
39  check_cxx_compiler_flag(-std=c++11 has_std_11_flag)
40  check_cxx_compiler_flag(-std=c++0x has_std_0x_flag)
41
42  if (has_std_11_flag)
43    set(CXX_STANDARD_FLAG -std=c++11)
44  elseif (has_std_0x_flag)
45    set(CXX_STANDARD_FLAG -std=c++0x)
46  endif ()
47endif ()
48
49set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG})
50
51# Check if variadic templates are working and not affected by GCC bug 39653:
52# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39653
53# Can be removed once gcc 4.4 support is dropped.
54check_cxx_source_compiles("
55  template <class T, class ...Types>
56  struct S { typedef typename S<Types...>::type type; };
57  int main() {}" SUPPORTS_VARIADIC_TEMPLATES)
58if (NOT SUPPORTS_VARIADIC_TEMPLATES)
59  set (SUPPORTS_VARIADIC_TEMPLATES OFF)
60endif ()
61
62# Check if user-defined literals are available
63check_cxx_source_compiles("
64  void operator\"\" _udl(long double);
65  int main() {}"
66  SUPPORTS_USER_DEFINED_LITERALS)
67if (NOT SUPPORTS_USER_DEFINED_LITERALS)
68  set (SUPPORTS_USER_DEFINED_LITERALS OFF)
69endif ()
70
71# Check if <variant> is available
72set(CMAKE_REQUIRED_FLAGS -std=c++1z)
73check_cxx_source_compiles("
74  #include <variant>
75  int main() {}"
76  FMT_HAS_VARIANT)
77if (NOT FMT_HAS_VARIANT)
78  set (FMT_HAS_VARIANT OFF)
79endif ()
80
81set(CMAKE_REQUIRED_FLAGS )
82