Link subproject object files directly.

Instead of merging all subproject object files into subproject.o, we now create subproject.txt containing a list of all object files, and use these directly in SUBPROJECT_OBJ_FILES.

ChangeLog

@@ -1,3 +1,16 @@
+2021-01-29  Frederik Seiffert <[email protected]>
+
+	* Instance/rules.make:
+	* Instance/subproject.make:
+	* common.make:
+	Link subproject object files directly. Instead of merging all
+	subproject object files into subproject.o, we now create
+	subproject.txt containing a list of all object files, and use these
+	directly in SUBPROJECT_OBJ_FILES.
+	This enables building on platforms like Windows MSVC where `ld -r` is
+	not supported, and generally avoids issues with incremental linking
+	that have historically existed in some linker versions.
+
 2021-01-18  Fred Kiefer <[email protected]>
 
 	* Documentation/news.texi: Update for upcoming release.

Instance/rules.make

@@ -206,7 +206,9 @@ endif
 
 ifneq ($($(GNUSTEP_INSTANCE)_SUBPROJECTS),)
 SUBPROJECT_OBJ_FILES = $(foreach d, $($(GNUSTEP_INSTANCE)_SUBPROJECTS), \
-    $(addprefix $(GNUSTEP_BUILD_DIR)/$(d)/, $(GNUSTEP_OBJ_DIR_NAME)/$(SUBPROJECT_PRODUCT)))
+    $(foreach o, $(shell cat \
+    $(GNUSTEP_BUILD_DIR)/$(d)/$(GNUSTEP_OBJ_DIR_NAME)/$(SUBPROJECT_PRODUCT)), \
+    $(addprefix $(GNUSTEP_BUILD_DIR)/$(d)/, $(o))))
 endif
 
 OBJC_OBJS = $(patsubst %.m,%.m$(OEXT),$($(GNUSTEP_INSTANCE)_OBJC_FILES))

Instance/subproject.make

@@ -58,7 +58,7 @@ $(GNUSTEP_OBJ_DIR)/$(SUBPROJECT_PRODUCT): $(OBJ_FILES_TO_LINK)
 ifeq ($(OBJ_FILES_TO_LINK),)
 	$(WARNING_EMPTY_LINKING)
 endif
-	$(ECHO_LINKING)$(OBJ_MERGE_CMD)$(END_ECHO)
+	@echo "$(OBJ_FILES_TO_LINK)" > $(GNUSTEP_OBJ_DIR)/$(SUBPROJECT_PRODUCT)
 
 #
 # Build-header target for framework subprojects

common.make

@@ -815,7 +815,7 @@ endif
 #
 # Common variables for subprojects
 #
-SUBPROJECT_PRODUCT = subproject$(OEXT)
+SUBPROJECT_PRODUCT = subproject.txt
 
 #
 # Set JAVA_HOME if not set.