From 21ae83adf679151715aa61518b6226dd7ad8e8e9 Mon Sep 17 00:00:00 2001
From: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>
Date: Fri, 18 Mar 2022 10:47:25 +0100
Subject: [PATCH 1/2] Only set Fortran arguments for Fortran compiler

---
 CMakeLists.txt            | 32 +++++------------------
 config/DefaultFlags.cmake | 54 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 25 deletions(-)
 create mode 100644 config/DefaultFlags.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 17efb8e27..0b78699e8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,8 @@
 cmake_minimum_required(VERSION 3.14.0)
+
+# Include overwrites before setting up the project
+set(CMAKE_USER_MAKE_RULES_OVERRIDE ${CMAKE_CURRENT_SOURCE_DIR}/config/DefaultFlags.cmake)
+
 project(fortran_stdlib
         LANGUAGES Fortran
         DESCRIPTION "Community driven and agreed upon de facto standard library for Fortran"
@@ -22,31 +26,9 @@ include(${PROJECT_SOURCE_DIR}/cmake/stdlib.cmake)
 # --- CMake specific configuration and package data export
 add_subdirectory(config)
 
-# --- compiler options
-if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU)
-  if(CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 9.0)
-    message(FATAL_ERROR "GCC Version 9 or newer required")
-  endif()
-  add_compile_options(-fimplicit-none)
-  add_compile_options(-ffree-line-length-132)
-  add_compile_options(-fno-range-check) # Needed for gfortran 9 and
-  # earlier for hash functions 
-  add_compile_options(-Wall)
-  add_compile_options(-Wextra)
-  add_compile_options(-Wimplicit-procedure)
-  # -pedantic-errors triggers a false positive for optional arguments of elemental functions,
-  # see test_optval and https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95446
-  if(CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 11.0)
-    add_compile_options(-pedantic-errors)
-  endif()
-  add_compile_options(-std=f2018)
-elseif(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")
-  if(WIN32)
-    set(fortran_flags /stand:f18 /warn:declarations,general,usage,interfaces,unused)
-  else()
-    set(fortran_flags -stand f18 -warn declarations,general,usage,interfaces,unused)
-  endif()
-  add_compile_options("$<$<COMPILE_LANGUAGE:Fortran>:${fortran_flags}>")
+# --- compiler selection
+if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU AND CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 9.0)
+  message(FATAL_ERROR "GCC Version 9 or newer required")
 endif()
 
 # --- compiler feature checks
diff --git a/config/DefaultFlags.cmake b/config/DefaultFlags.cmake
new file mode 100644
index 000000000..b07a170ee
--- /dev/null
+++ b/config/DefaultFlags.cmake
@@ -0,0 +1,54 @@
+if(CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+  set(
+    CMAKE_Fortran_FLAGS_INIT
+    "-fimplicit-none"
+    "-ffree-line-length-132"
+    "-fno-range-check"
+  )
+  set(
+    CMAKE_Fortran_FLAGS_RELEASE_INIT
+  )
+  set(
+    CMAKE_Fortran_FLAGS_DEBUG_INIT
+    "-Wall"
+    "-Wextra"
+    "-Wimplicit-procedure"
+    "-std=f2018"
+  )
+elseif(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")
+  set(
+    CMAKE_Fortran_FLAGS_INIT
+  )
+  set(
+    CMAKE_Fortran_FLAGS_RELEASE_INIT
+  )
+  if(WIN32)
+    set(
+      CMAKE_Fortran_FLAGS_DEBUG_INIT
+      "/stand:f18"
+      "/warn:declarations,general,usage,interfaces,unused"
+    )
+  else()
+    set(
+      CMAKE_Fortran_FLAGS_RELEASE_INIT
+    )
+    set(
+      CMAKE_Fortran_FLAGS_DEBUG_INIT
+      "-stand f18"
+      "-warn declarations,general,usage,interfaces,unused"
+    )
+  endif()
+else()
+  set(
+    CMAKE_Fortran_FLAGS_INIT
+  )
+  set(
+    CMAKE_Fortran_FLAGS_RELEASE_INIT
+  )
+  set(
+    CMAKE_Fortran_FLAGS_DEBUG_INIT
+  )
+endif()
+string(REPLACE ";" " " CMAKE_Fortran_FLAGS_INIT "${CMAKE_Fortran_FLAGS_INIT}")
+string(REPLACE ";" " " CMAKE_Fortran_FLAGS_RELEASE_INIT "${CMAKE_Fortran_FLAGS_RELEASE_INIT}")
+string(REPLACE ";" " " CMAKE_Fortran_FLAGS_DEBUG_INIT "${CMAKE_Fortran_FLAGS_DEBUG_INIT}")

From 5cc198b735e03c792e16ce6125702c8bafda97a7 Mon Sep 17 00:00:00 2001
From: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>
Date: Fri, 18 Mar 2022 15:25:49 +0100
Subject: [PATCH 2/2] Remove superfluous CMAKE_Fortran_FLAGS_RELEASE_INIT

---
 config/DefaultFlags.cmake | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/config/DefaultFlags.cmake b/config/DefaultFlags.cmake
index b07a170ee..f8c8d5367 100644
--- a/config/DefaultFlags.cmake
+++ b/config/DefaultFlags.cmake
@@ -29,9 +29,6 @@ elseif(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")
       "/warn:declarations,general,usage,interfaces,unused"
     )
   else()
-    set(
-      CMAKE_Fortran_FLAGS_RELEASE_INIT
-    )
     set(
       CMAKE_Fortran_FLAGS_DEBUG_INIT
       "-stand f18"