add rp() and bp() in internal.h.

debug utility macro rp() (rp_m()) and bp() are introduced.
* rp(obj) shows obj information w/o any side-effect to STDERR.
* rp_m(m, obj) is similar to rp(obj), but show m before.
* bp() is alias of ruby_debug_breakpoint(), which is registered
  as a breakpoint in run.gdb (used by `make gdb` or make gdb-ruby`).

common.mk

@@ -3035,7 +3035,6 @@ thread.$(OBJEXT): {$(VPATH)}debug_counter.h
 thread.$(OBJEXT): {$(VPATH)}defines.h
 thread.$(OBJEXT): {$(VPATH)}encoding.h
 thread.$(OBJEXT): {$(VPATH)}eval_intern.h
-thread.$(OBJEXT): {$(VPATH)}gc.h
 thread.$(OBJEXT): {$(VPATH)}hrtime.h
 thread.$(OBJEXT): {$(VPATH)}id.h
 thread.$(OBJEXT): {$(VPATH)}intern.h

gc.h

@@ -100,7 +100,6 @@ int ruby_get_stack_grow_direction(volatile VALUE *addr);
 
 const char *rb_obj_info(VALUE obj);
 const char *rb_raw_obj_info(char *buff, const int buff_size, VALUE obj);
-void rb_obj_info_dump(VALUE obj);
 
 VALUE rb_gc_disable_no_rest(void);
 

internal.h

@@ -1388,6 +1388,22 @@ rb_ary_entry_internal(VALUE ary, long offset)
     return ptr[offset];
 }
 
+/* MRI debug support */
+void rb_obj_info_dump(VALUE obj);
+void  ruby_debug_breakpoint(void);
+
+// show obj data structure without any side-effect
+#define rp(obj) rb_obj_info_dump((VALUE)obj);
+// same as rp, but add message header
+#define rp_m(msg, obj) do { \
+    fprintf(stderr, "%s", (msg)); \
+    rb_obj_info_dump((VALUE)obj); \
+} while (0)
+
+// `ruby_debug_breakpoint()` does nothing,
+// but breakpoint is set in run.gdb, so `make gdb` can stop here.
+#define bp() ruby_debug_breakpoint()
+
 /* bignum.c */
 extern const char ruby_digitmap[];
 double rb_big_fdiv_double(VALUE x, VALUE y);

thread.c

@@ -66,7 +66,6 @@
 #include "ruby/config.h"
 #include "ruby/io.h"
 #include "eval_intern.h"
-#include "gc.h"
 #include "timev.h"
 #include "ruby/thread.h"
 #include "ruby/thread_native.h"

vm_debug.h

@@ -22,13 +22,10 @@ RUBY_SYMBOL_EXPORT_BEGIN
 #define dpi(i)   ruby_debug_print_id(-1, 0, "", (i))
 #define dpn(n)   ruby_debug_print_node(-1, 0, "", (n))
 
-#define bp()     ruby_debug_breakpoint()
-
 VALUE ruby_debug_print_value(int level, int debug_level, const char *header, VALUE v);
 ID    ruby_debug_print_id(int level, int debug_level, const char *header, ID id);
 NODE *ruby_debug_print_node(int level, int debug_level, const char *header, const NODE *node);
 int   ruby_debug_print_indent(int level, int debug_level, int indent_level);
-void  ruby_debug_breakpoint(void);
 void  ruby_debug_gc_check_func(void);
 void ruby_set_debug_option(const char *str);