From b27a42207633beda9a9d02036c0ff8d941ebf882 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Tue, 17 Dec 2019 21:10:35 +0100
Subject: [PATCH] Preeliminary clang support added

---
 conanfile.py                            | 12 ++++----
 src/CMakeLists.txt                      | 15 +++++++---
 src/include/units/bits/external/hacks.h | 37 +++++++++++++++++--------
 3 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/conanfile.py b/conanfile.py
index fba6d3c0..d81d33e7 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -59,10 +59,12 @@ class UnitsConan(ConanFile):
         return tools.get_env("CONAN_RUN_TESTS", False)
 
     def configure(self):
-        if self.settings.compiler != "gcc":
-            raise ConanInvalidConfiguration("Library works only with gcc")
-        if Version(self.settings.compiler.version) < "9":
-            raise ConanInvalidConfiguration("Library requires at least gcc-9")
+        if self.settings.compiler != "gcc": # and self.settings.compiler != "clang":
+            raise ConanInvalidConfiguration("Library works only with gcc") # and clang")
+        if self.settings.compiler == "gcc" and Version(self.settings.compiler.version) < "9":
+            raise ConanInvalidConfiguration("Library requires at least g++-9")
+        if self.settings.compiler == "clang" and Version(self.settings.compiler.version) < "11":
+            raise ConanInvalidConfiguration("Library requires at least clang++-11")
         if self.settings.compiler.cppstd not in ["20", "gnu20"]:
             raise ConanInvalidConfiguration("Library requires at least C++20 support")
 
@@ -75,7 +77,7 @@ class UnitsConan(ConanFile):
         return cmake
 
     def requirements(self):
-        if Version(self.settings.compiler.version) < "10":
+        if self.settings.compiler == "clang" or Version(self.settings.compiler.version) < "10":
             self.requires("range-v3/0.10.0@ericniebler/stable")
 
     def build(self):
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0f0d6720..1c0e8430 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -60,12 +60,18 @@ target_include_directories(units
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
         $<INSTALL_INTERFACE:include>
 )
-if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
-    target_compile_options(units
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    target_link_libraries(units
         INTERFACE
-            -Wno-literal-suffix
-            -Wno-non-template-friend
+            CONAN_PKG::range-v3
     )
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(units
+    INTERFACE
+        -Wno-literal-suffix
+        -Wno-non-template-friend
+    )
+
     if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.0)
         target_compile_options(units
             INTERFACE
@@ -77,6 +83,7 @@ if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
         )
     endif()
 endif()
+
 add_library(mp::units ALIAS units)
 
 # installation info
diff --git a/src/include/units/bits/external/hacks.h b/src/include/units/bits/external/hacks.h
index c1bb861a..3539ae33 100644
--- a/src/include/units/bits/external/hacks.h
+++ b/src/include/units/bits/external/hacks.h
@@ -24,6 +24,13 @@
 
 #include <functional>
 
+#if __clang__
+#define COMP_CLANG __clang_major__
+#elif __GNUC__
+#define COMP_GCC __GNUC__
+#define COMP_GCC_MINOR __GNUC_MINOR__
+#endif
+
 #ifdef NDEBUG
 #define Expects(cond) (void)(cond);
 #else
@@ -31,23 +38,36 @@
 #define Expects(cond) assert(cond);
 #endif
 
-#if __GNUC__ < 10
+#if COMP_GCC >= 10 || COMP_CLANG >= 11
 
-#include <concepts/concepts.hpp>
-#define AUTO
-#define SAME_AS(T) T
+#include <concepts>
 
 #else
 
-#include <concepts>
+#include <concepts/concepts.hpp>
+
+#endif
+
+#if COMP_GCC >= 10 || COMP_CLANG >= 11
+
 #define AUTO auto
 #define SAME_AS(T) std::same_as<T>
 
+#else
+
+#define AUTO
+#define SAME_AS(T) T
+
 #endif
 
 namespace std {
 
-#if __GNUC__ < 10
+#if COMP_GCC >= 10
+
+  template<class T>
+  concept default_constructible = constructible_from<T>;
+
+#else
 
   // concepts
   using concepts::common_reference_with;
@@ -71,11 +91,6 @@ namespace std {
   template<class F, class... Args>
   concept regular_invocable = invocable<F, Args...>;
 
-#else
-
-template<class T>
-concept default_constructible = constructible_from<T>;
-
 #endif
 
 } // namespace std