Support building on Windows with Clang MSVC target

ChangeLog

@@ -1,3 +1,14 @@
+2021-01-29  Frederik Seiffert <frederik@algoriddim.com>
+
+	* common.make:
+	* configure:
+	* m4/gs_cc_is_clang.m4:
+	* target.make:
+	Added support for building on Windows with Clang MSVC target.
+	Requires passing a host like --host=x86_64-pc-windows.
+	Removes the check for $GCC in gs_cc_is_clang.m4 as it will be false
+	when using the MSVC ABI due to __GNUC__ not being defined.
+
 2021-01-29  Frederik Seiffert <frederik@algoriddim.com>
 
 	* common.make:

Instance/library.make

@@ -200,9 +200,15 @@ endif
 else # BUILD_DLL
 
 # When you build a DLL, you have to install it in a directory which is
-# in your PATH.
+# in your PATH. On Windows MSVC we use the library directory that will
+# also contain other libraries like objc.dll. Otherwise (i.e. on MinGW)
+# we use the tools directory.
 ifeq ($(DLL_INSTALLATION_DIR),)
-  DLL_INSTALLATION_DIR = $(GNUSTEP_TOOLS)/$(GNUSTEP_TARGET_LDIR)
+  ifeq ($(GNUSTEP_TARGET_OS), windows)
+    DLL_INSTALLATION_DIR = $(FINAL_LIBRARY_INSTALL_DIR)
+  else
+    DLL_INSTALLATION_DIR = $(GNUSTEP_TOOLS)/$(GNUSTEP_TARGET_LDIR)
+  endif
 endif
 
 # When we build a DLL, we also pass -DBUILD_lib{library_name}_DLL=1 to
@@ -219,8 +225,13 @@ endif
 CLEAN_library_NAME = $(subst -,_,$(LIBRARY_NAME_WITH_LIB))
 SHARED_CFLAGS += -DBUILD_$(CLEAN_library_NAME)_DLL=1
 
-# LIBRARY_FILE is the import library, libgnustep-base.dll.a
-LIBRARY_FILE         = $(LIBRARY_NAME_WITH_LIB)$(DLL_LIBEXT)$(LIBEXT)
+# LIBRARY_FILE is the import library, i.e. gnustep-base.lib for Windows
+# MSVC, or libgnustep-base.dll.a for MinGW.
+ifeq ($(GNUSTEP_TARGET_OS), windows)
+  LIBRARY_FILE         = $(LIBRARY_NAME_WITHOUT_LIB)$(LIBEXT)
+else
+  LIBRARY_FILE         = $(LIBRARY_NAME_WITH_LIB)$(DLL_LIBEXT)$(LIBEXT)
+endif
 VERSION_LIBRARY_FILE = $(LIBRARY_FILE)
 SONAME_LIBRARY_FILE  = $(LIBRARY_FILE)
 
@@ -230,6 +241,9 @@ SONAME_LIBRARY_FILE  = $(LIBRARY_FILE)
 # INTERFACE_VERSION of the library; this works exactly in the same way
 # as under Unix.
 LIB_LINK_DLL_FILE    = $(DLL_PREFIX)$(LIBRARY_NAME_WITHOUT_LIB)-$(subst .,_,$(INTERFACE_VERSION))$(DLL_LIBEXT)
+ifeq ($(GNUSTEP_TARGET_OS), windows)
+  LIB_LINK_PDB_FILE  = $(DLL_PREFIX)$(LIBRARY_NAME_WITHOUT_LIB)-$(subst .,_,$(INTERFACE_VERSION))$(DLL_PDBEXT)
+endif
 endif # BUILD_DLL
 
 else # following code for static libs
@@ -326,6 +340,15 @@ internal-install-lib::
 	  $(INSTALL_PROGRAM) $(GNUSTEP_OBJ_DIR)/$(LIB_LINK_DLL_FILE) \
 	                     $(DLL_INSTALLATION_DIR) ; \
 	fi$(END_ECHO)
+
+ifeq ($(GNUSTEP_TARGET_OS), windows)
+# On Windows MSVC, also install the PDB file.
+internal-install-lib::
+	$(ECHO_INSTALLING)if [ -f $(GNUSTEP_OBJ_DIR)/$(LIB_LINK_PDB_FILE) ]; then \
+	  $(INSTALL_PROGRAM) $(GNUSTEP_OBJ_DIR)/$(LIB_LINK_PDB_FILE) \
+	                     $(DLL_INSTALLATION_DIR) ; \
+	fi$(END_ECHO)
+endif
 endif
 
 internal-library-uninstall_:: shared-instance-headers-uninstall shared-instance-pkgconfig-uninstall

configure

@@ -4474,10 +4474,8 @@ if ${_gs_cv_cc_is_clang+:} false; then :
   $as_echo_n "(cached) " >&6
 else
       _gs_cv_cc_is_clang="no"
-    if test x"${GCC}" = x"yes" ; then
-        if "${CC}" -v 2>&1 | grep -q 'clang version'; then
-            _gs_cv_cc_is_clang="yes";
-        fi
+    if "${CC}" -v 2>&1 | grep -q 'clang version'; then
+        _gs_cv_cc_is_clang="yes";
     fi
 
 fi

m4/gs_cc_is_clang.m4

@@ -14,10 +14,8 @@ AC_DEFUN([GS_CHECK_CC_IS_CLANG],dnl
   [AC_REQUIRE([AC_PROG_CC])
     AC_CACHE_CHECK([whether the compiler is clang],[_gs_cv_cc_is_clang], [dnl
     _gs_cv_cc_is_clang="no"
-    if test x"${GCC}" = x"yes" ; then
-        if "${CC}" -v 2>&1 | grep -q 'clang version'; then
-            _gs_cv_cc_is_clang="yes";
-        fi
+    if "${CC}" -v 2>&1 | grep -q 'clang version'; then
+        _gs_cv_cc_is_clang="yes";
     fi
     ])
     AS_VAR_SET([gs_cv_cc_is_clang], [${_gs_cv_cc_is_clang}])

target.make

@@ -34,7 +34,10 @@ endif
 #
 # Target specific libraries
 #
-TARGET_SYSTEM_LIBS = $(CONFIG_SYSTEM_LIBS) -lm
+TARGET_SYSTEM_LIBS = $(CONFIG_SYSTEM_LIBS)
+ifneq ($(GNUSTEP_TARGET_OS), windows)
+	TARGET_SYSTEM_LIBS += -lm
+endif
 
 # All code we build needs to be thread-safe nowadays
 INTERNAL_CFLAGS = -pthread
@@ -60,6 +63,10 @@ else ifeq ($(findstring mingw64, $(GNUSTEP_TARGET_OS)), mingw64)
   TARGET_SYSTEM_LIBS = $(CONFIG_SYSTEM_LIBS) \
 	-lws2_32 -ladvapi32 -lcomctl32 -luser32 -lcomdlg32 \
 	-lmpr -lnetapi32 -lm -I. # the -I is a dummy to avoid -lm^M
+else ifeq ($(GNUSTEP_TARGET_OS), windows)
+  TARGET_SYSTEM_LIBS = $(CONFIG_SYSTEM_LIBS) \
+	-lws2_32 -ladvapi32 -lcomctl32 -luser32 -lcomdlg32 \
+	-lmpr -lnetapi32 -lkernel32 -lshell32
 endif
 
 ifeq ($(findstring solaris, $(GNUSTEP_TARGET_OS)), solaris)
@@ -808,7 +815,7 @@ SHARED_CFLAGS =
 # while it is the default, it might silently get disabled if a symbol
 # gets manually exported (eg, because a header of a library we include
 # exports a symbol by mistake).
-ifneq ($(CC),clang)
+ifneq ($(CLANG_CC), yes)
 SHARED_LIB_LINK_CMD     = \
         $(LD) $(SHARED_LD_PREFLAGS) -shared \
         -Wl,--enable-auto-image-base \
@@ -1045,6 +1052,56 @@ endif
 #
 ####################################################
 
+####################################################
+#
+# Windows MSVC
+#
+ifeq ($(GNUSTEP_TARGET_OS), windows)
+shared = yes
+HAVE_SHARED_LIBS = yes
+
+# This command links the library, generates the list of symbols to export from
+# the dllexport annotations, creates the DLL (eg, obj/gnustep-base-1_13.dll),
+# a PDB file (eg, obj/gnustep-base-1_13.pdb, requires -g flag), and the import
+# library (eg, obj/gnustep-base.lib).
+SHARED_LIB_LINK_CMD     = \
+	$(LD) $(SHARED_LD_PREFLAGS) -g -Wl,-dll \
+	-Wl,-implib:$(LIB_LINK_OBJ_DIR)/$(LIB_LINK_VERSION_FILE) \
+	-Wl,-pdb:$(LIB_LINK_OBJ_DIR)/$(LIB_LINK_PDB_FILE) \
+	$(ALL_LDFLAGS) -o $(LIB_LINK_OBJ_DIR)/$(LIB_LINK_DLL_FILE) $^ \
+	$(INTERNAL_LIBRARIES_DEPEND_UPON) \
+	$(SHARED_LD_POSTFLAGS)
+
+AFTER_INSTALL_SHARED_LIB_CMD =
+AFTER_INSTALL_SHARED_LIB_CHOWN =
+
+BUILD_DLL	 = yes
+LIBEXT	 	 = .lib
+SHARED_LIBEXT    = .lib
+DLL_LIBEXT	 = .dll
+DLL_PDBEXT	 = .pdb
+#SHARED_CFLAGS	 +=
+
+OBJ_MERGE_CMD = ar cr $(GNUSTEP_OBJ_DIR)/$(SUBPROJECT_PRODUCT) $^ ;
+
+HAVE_BUNDLES   = yes
+BUNDLE_LD      = $(LD)
+
+BUNDLE_LDFLAGS += -Wl,-dll
+BUNDLE_LINK_CMD  = \
+	$(BUNDLE_LD) $(BUNDLE_LDFLAGS) $(ALL_LDFLAGS) \
+	-o $(LDOUT)$(BUNDLE_FILE) \
+	$(OBJ_FILES_TO_LINK) \
+	$(BUNDLE_LIBFLAGS) $(ALL_LIB_DIRS) $(BUNDLE_LIBS)
+
+# On Windows MSVC, class name symbols start with '__'
+EXTRACT_CLASS_NAMES_COMMAND = $(NM) -Pg $$object_file | sed -n -e '/^._OBJC_CLASS_[A-Za-z0-9_.]* [^U]/ {s/^._OBJC_CLASS_\([A-Za-z0-9_.]*\) [^U].*/\1/p;}' -e '/^__objc_class_name_[A-Za-z0-9_.]* [^U]/ {s/^__objc_class_name_\([A-Za-z0-9_.]*\) [^U].*/\1/p;}'
+
+endif
+
+# end Windows MSVC
+#
+####################################################
 
 ####################################################
 #