From 8af633b1c3944cbd471cb1734e9bf80399281a6a Mon Sep 17 00:00:00 2001
From: Peter Urban <peter.urban@ugent.be>
Date: Tue, 17 Sep 2024 13:09:32 +0200
Subject: [PATCH] Use CC variable in the Makefile directly

---
 .../workflows/test-alternative-compilers.yml  | 57 +++++++++++--------
 Makefile                                      | 24 +++++++-
 TOOLS.gcc                                     |  9 +--
 TOOLS.ini                                     | 21 +++++--
 4 files changed, 73 insertions(+), 38 deletions(-)

diff --git a/.github/workflows/test-alternative-compilers.yml b/.github/workflows/test-alternative-compilers.yml
index 4f30d1a..f4e2e0b 100644
--- a/.github/workflows/test-alternative-compilers.yml
+++ b/.github/workflows/test-alternative-compilers.yml
@@ -14,55 +14,66 @@ jobs:
         include:
             - name: windows / clang-cl (c++)
               os: windows-latest
-              compiler: 'clang-cl /TP'
-              make_tool: "nmake"
+              compiler: 'clang-cl' # /TP forces the file to be compiled as C++
+              make_command: "nmake CC=$CC"
             - name: linux / g++ (c++)
               os: ubuntu-latest
-              compiler: 'g++ -x c++'
-              make_tool: "make"
+              compiler: 'g++'
+              extra_flags: '-x c++'
+              make_command: "make CC=$CC EXTRA_FLAGS=$EXTRA_FLAGS"
             - name: linux / clang (c)
               os: ubuntu-latest
               compiler: 'clang'
-              make_tool: "make"
+              make_command: "make CC=$CC"
             - name: linux / clang (c++)
               os: ubuntu-latest
-              compiler: 'clang -x c++'
-              make_tool: "make"
+              compiler: 'clang'
+              extra_flags: '-x c++'
+              make_command: "make CC=$CC EXTRA_FLAGS=$EXTRA_FLAGS"
             - name: macos / g++ (c++)
               os: macos-latest
-              compiler: 'g++ -x c++'
-              make_tool: "make"
+              compiler: 'g++'
+              extra_flags: '-x c++'
+              make_command: "make CC=$CC EXTRA_FLAGS=$EXTRA_FLAGS"
             - name: macos / clang (c)
               os: macos-latest
               compiler: 'clang'
-              make_tool: "make"
+              make_command: "make CC=$CC"
             - name: macos / clang (c++)
               os: macos-latest
-              compiler: 'clang -x c++'
-              make_tool: "make"
+              compiler: 'clang'
+              extra_flags: '-x c++'
+              make_command: "make CC=$CC EXTRA_FLAGS=$EXTRA_FLAGS"
       fail-fast: false
 
+    env:
+      CC: ${{ matrix.compiler }}
+      EXTRA_FLAGS: ${{ matrix.extra_flags }}
+
     steps:
     - uses: actions/checkout@v4
     - uses: ilammy/msvc-dev-cmd@v1
 
-    - name: Check COMPILER variable
+    - name: Check CC variable
       shell: bash
-      env:
-        COMPILER: ${{ matrix.compiler }}
       run: |
-        output=$(${{ matrix.make_tool }} name_compiler)
-        echo "$output"
-        if [[ "$output" != *"${{ matrix.compiler }}"* ]]; then
-          echo "COMPILER '${{ matrix.compiler }}'' variable not used by the make file!"
-          #exit 1
+        compiler=$(${{ matrix.make_command }} name_compiler)
+        extra_flags=$(${{ matrix.make_command }} name_extra_flags)
+        echo "compile command: $compiler $extra_flags"
+        if [[ "$compiler" != *"${{ matrix.compiler }}"* ]]; then
+          echo "CC '${{ matrix.compiler }}'' variable not used by the make file!"
+          exit 1
+        fi
+        if  [[ "${{ matrix.extra_flags }}" != "" ]]; then
+          if [[ "$extra_flags" != *"${{ matrix.extra_flags }}"* ]]; then
+            echo "CC '${{ matrix.extra_flags }}'' variable not used by the make file!"
+            exit 1
+          fi
         fi
 
     - name: Compile
       shell: bash
-      env:
-        COMPILER: ${{ matrix.compiler }}
-      run: ${{ matrix.make_tool }}
+      run: ${{ matrix.make_command }}
 
     - name: Tests
       shell: bash
diff --git a/Makefile b/Makefile
index 0b5b252..fcb0237 100644
--- a/Makefile
+++ b/Makefile
@@ -7,25 +7,43 @@ PROGRAM_SOURCES = gsw_check_functions.c\
 LIBRARY_SRCS    = gsw_oceanographic_toolbox.c \
                   gsw_saar.c
 
+# This includes TOOLS.gcc if make (unix) is used
+# The #\ logic causes the include to be ignored by nmake (windows)
+# nmake automatically includes TOOLS.ini
 # \
 !ifdef 0 #
 include TOOLS.gcc # \
 !endif # \
 #
 
+# --- NOTES ---:
+# (1) The default CC variable is defined in the TOOLS.gcc file (make) / Tools.ini (nmake) file.
+#     use (n)make CC=compiler_command_of_choice to override the default compiler.
+# (2) On windows the default CC variable is cl with the option /TP. This causes the project to be compiled
+#     as C++ code on windows. This is necessary because msvc does not support C99 style complex numbers.
+#     See also notes in TOOLS.ini.
+
+
 all: $(Program) $(Library)
 
 $(Program):
-		$(COMPILER) $(CRELEASE) $(PROGRAM_SOURCES) $(LIBS) $(OUT)$(Program)$(X)
+		$(CC) $(CRELEASE) $(PROGRAM_SOURCES) $(LIBS) $(OUT)$(Program)$(X)
 
 library: $(Library)
 $(Library):
-		$(COMPILER) $(LFLAGS) $(LIBRARY_SRCS) $(LIBS) $(OUT)$(Library)$(SHARED_POSTFIX)
+		$(CC) $(LFLAGS) $(LIBRARY_SRCS) $(LIBS) $(OUT)$(Library)$(SHARED_POSTFIX)
 
 clean:
 		$(RM) *.o *.obj *.ilk *.pdb *.tmp *.i *~
 		$(RM) $(Library)$(SHARED_POSTFIX)
 		$(RM) $(Program)$(X)
 
+# Print the the CC variable (for debugging purpose).
+# This is useful to check if the correct compiler is used with the specified commands.
 name_compiler:
-		@echo $(COMPILER_NAME)
+		@echo $(CC)
+
+# Print the the EXTRA_FLAGS variable (for debugging purpose).
+# This is useful to check if the correct extra flags are used with the specified commands.
+name_extra_flags:
+		@echo $(EXTRA_FLAGS)
diff --git a/TOOLS.gcc b/TOOLS.gcc
index 71a44e1..fa838b0 100644
--- a/TOOLS.gcc
+++ b/TOOLS.gcc
@@ -3,16 +3,13 @@ CDEBUG          = -g
 LDEBUG          =
 CRELEASE        = -O3
 LRELEASE        =
-CFLAGS          = $(CRELEASE)
-LFLAGS          = -fPIC -shared $(LRELEASE)
+EXTRA_FLAGS     =
+CFLAGS          = $(CRELEASE) $(EXTRA_FLAGS)
+LFLAGS          = -fPIC -shared $(LRELEASE) $(EXTRA_FLAGS)
 OUT             = -o
 RM              = rm -f
 CP              = cp
 CC              = gcc
-CPP             = gcc
 X               =
 O               = .o
 SHARED_POSTFIX  = .so
-
-# Optionally set the compiler using the environment variable COMPILER
-COMPILER ?= $(CPP)
diff --git a/TOOLS.ini b/TOOLS.ini
index 8736bb7..6459dac 100644
--- a/TOOLS.ini
+++ b/TOOLS.ini
@@ -4,16 +4,25 @@ CDEBUG          = /Zi
 LDEBUG          =
 CRELEASE        = /Ox
 LRELEASE        = /Ox
-CFLAGS          = $(CRELEASE)
-LFLAGS          = /LD $(LRELEASE)
+EXTRA_FLAGS     = /TP
+CFLAGS          = $(CRELEASE) $(EXTRA_FLAGS)
+LFLAGS          = /LD $(LRELEASE) $(EXTRA_FLAGS)
 OUT             = /Fe
 RM              = del /F /Q
 CP              = copy
 CC              = cl
-CPP             = $(CC) /TP
 X               = .exe
 O               = .obj
 SHARED_POSTFIX  = .dll
-# set the compiler using the environment variable COMPILER
-# to override with environment variable use nmake /E
-COMPILER = $(CPP)
+
+# Notes: The EXTRA_FLAGS /TP causes the compiler to treat all .c files as C++ files
+# This is necessary on windows because the msvc C compiler does not support
+# standard c99 complex numbers. However, msvc does support the c++ standard
+# version of complex numbers (<complex>). The project automatically detects
+# if it is compiled in c or c++ mode and uses the appropriate header file.
+
+# If you want to use a different compiler (e.g clang-cl), you can set the CC variable
+# using e.g. nmake CC=clang-cl.
+# If this compiler is not compatible with the msvc compiler, you may need
+# to remove the EXTRA_FLAGS /TP option by setting EXTRA_FLAGS to an empty string.
+# e.g. nmake CC=gcc EXTRA_FLAGS=