Fix building without GC support. Still need to make sure that some of the GC functions always work, since they are expected to be no-ops in non-GC mode.

GNUmakefile

@@ -84,6 +84,7 @@ ifeq ($(boehm_gc), yes)
 libobjc_C_FILES += gc_boehm.c
 libobjc_LIBRARIES_DEPEND_UPON += -lgc-threaded
 libobjc_OBJCFLAGS += -fobjc-gc
+libobjc_CPPFLAGS += -DENABLE_GC
 endif
 
 

gc_boehm.c

@@ -10,7 +10,7 @@
 #include <stdio.h>
 #include "gc_ops.h"
 #define I_HIDE_POINTERS
-#include <gc.h>
+#include <gc/gc.h>
 #include <gc/gc_typed.h>
 
 #ifndef __clang__

gc_none.c

@@ -3,6 +3,7 @@
 #include "gc_ops.h"
 #include "class.h"
 #include <stdlib.h>
+#include <stdio.h>
 
 static id allocate_class(Class cls, size_t extraBytes)
 {
@@ -24,3 +25,12 @@ PRIVATE struct gc_ops *gc = &gc_ops_none;
 
 PRIVATE BOOL isGCEnabled = NO;
 
+#ifndef ENABLE_GC
+PRIVATE void enableGC(BOOL exclusive)
+{
+	fprintf(stderr, "Attempting to enable garbage collection, but your"
+			"Objective-C runtime was built without garbage collection"
+			"support\n");
+	abort();
+}
+#endif

gc_ops.h

@@ -32,6 +32,7 @@ struct gc_ops
  * -release / -autorelease messages become no-ops.
  */
 void enableGC(BOOL exclusive);
+
 /**
  * The mode for garbage collection
  */