use pragma(crt_constructor) instead of registration via C

Author: rainers

src/gc/proxy.d

@@ -13,8 +13,6 @@
  */
 module gc.proxy;
 
-import gc.impl.conservative.gc;
-import gc.impl.manual.gc;
 import gc.impl.proto.gc;
 import gc.config;
 import gc.gcinterface;
@@ -37,11 +35,27 @@ private
 
 extern (C)
 {
+    // do not import GC modules, they might add a dependency to this whole module
+    void _d_register_conservative_gc();
+    void _d_register_manual_gc();
+
+    // if you don't want to include the default GCs, replace during link by another implementation
+    void* register_default_gcs()
+    {
+        pragma(inline, false);
+        // do not call, they register implicitly through pragma(crt_constructor)
+        // avoid being optimized away
+        auto reg1 = &_d_register_conservative_gc;
+        auto reg2 = &_d_register_manual_gc;
+        return reg1 < reg2 ? reg1 : reg2;
+    }
+
     void gc_init()
     {
         instanceLock.lock();
         if (!isInstanceInit)
         {
+            register_default_gcs();
             config.initialize();
             auto protoInstance = instance;
             auto newInstance = createGCInstance(config.gc);

src/gc/register.c

@@ -10,12 +10,8 @@ $(ROOT)/%.done: $(ROOT)/%
 	$(QUIET)$(TIMELIMIT)$(ROOT)/$* $(RUN_ARGS)
 	@touch $@
 
-$(ROOT)/custom_gc: $(ROOT)/register_custom_gc.o
 $(ROOT)/%: $(SRC)/%.d
-	$(QUIET)$(DMD) $(DFLAGS) -of$@ $^
-
-$(ROOT)/register_custom_gc.o: $(SRC)/register_custom_gc.c
-	$(QUIET)$(CC) -c $(CFLAGS) -o $@ $^
+	$(QUIET)$(DMD) $(DFLAGS) -of$@ $<
 
 clean:
 	rm -rf $(ROOT)

test/init_fini/Makefile

@@ -6,11 +6,16 @@ static import core.memory;
 
 extern (C) __gshared string[] rt_options = ["gcopt=gc:malloc"];
 
-extern (C) void register_mygc()
+extern (C) pragma(crt_constructor) void register_mygc()
 {
     registerGCFactory("malloc", &MallocGC.initialize);
 }
 
+extern (C) void register_default_gcs()
+{
+    // remove default GCs
+}
+
 /** Simple GC that requires any pointers passed to it's API
     to point to start of the allocation.
  */

test/init_fini/src/custom_gc.d

@@ -0,0 +1,13 @@
+# built from the druntime top-level folder
+# to be overwritten by caller
+DMD=dmd
+MODEL=64
+DRUNTIMELIB=druntime64.lib
+
+test: custom_gc
+
+custom_gc:
+	$(DMD) -m$(MODEL) -conf= -Isrc -defaultlib=$(DRUNTIMELIB) test\init_fini\src\custom_gc.d
+	custom_gc.exe
+	del custom_gc.exe custom_gc.obj
+

test/init_fini/src/register_custom_gc.c

@@ -105,7 +105,10 @@ test_hash:
 test_stdcpp:
 	$(MAKE) -f test\stdcpp\win64.mak "DMD=$(DMD)" MODEL=$(MODEL) "VCDIR=$(VCDIR)" DRUNTIMELIB=$(DRUNTIME) "CC=$(CC)" test
 
-test_all:  test_uuid test_aa test_hash test_stdcpp
+custom_gc:
+	$(MAKE) -f test\init_fini\win64.mak "DMD=$(DMD)" MODEL=$(MODEL) "VCDIR=$(VCDIR)" DRUNTIMELIB=$(DRUNTIME) "CC=$(CC)" test
+
+test_all:  test_uuid test_aa test_hash test_stdcpp custom_gc
 
 ################### zip/install/clean ##########################