* variable.c (rb_const_set): show the previous definition

  location.  [EXPERIMENTAL]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33175 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Sun Sep  4 00:11:49 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* variable.c (rb_const_set): show the previous definition
+	  location.  [EXPERIMENTAL]
+
 Sat Sep  3 23:56:24 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (sizeof_struct_dirent_too_small): check if struct

constant.h

@@ -19,6 +19,8 @@ typedef enum {
 typedef struct rb_const_entry_struct {
     rb_const_flag_t flag;
     VALUE value;            /* should be mark */
+    VALUE file;
+    int line;
 } rb_const_entry_t;
 
 VALUE rb_mod_private_constant(int argc, VALUE *argv, VALUE obj);

gc.c

@@ -1569,6 +1569,7 @@ mark_const_entry_i(ID key, const rb_const_entry_t *ce, st_data_t data)
 {
     struct mark_tbl_arg *arg = (void*)data;
     gc_mark(arg->objspace, ce->value, arg->lev);
+    gc_mark(arg->objspace, ce->file, arg->lev);
     return ST_CONTINUE;
 }
 

internal.h

@@ -195,6 +195,7 @@ void rb_vm_change_state(void);
 void rb_vm_inc_const_missing_count(void);
 void rb_thread_mark(void *th);
 const void **rb_vm_get_insns_address_table(void);
+VALUE rb_sourcefilename(void);
 
 /* vm_dump.c */
 void rb_vm_bugreport(void);

test/ruby/test_const.rb

@@ -45,4 +45,13 @@ def test_const
     assert defined?(TEST4)
     assert_equal 8, TEST4
   end
+
+  def test_redefinition
+    c = Class.new
+    c.const_set(:X, 1)
+    assert_output(nil, <<-WARNING) {c.const_set(:X, 2)}
+#{__FILE__}:#{__LINE__-1}: warning: already initialized constant X
+#{__FILE__}:#{__LINE__-3}: warning: previous definition of X was here
+WARNING
+  end
 end

variable.c

@@ -2057,8 +2057,13 @@ rb_const_set(VALUE klass, ID id, VALUE val)
 		autoload_delete(klass, id);
 	    }
 	    else {
+		const char *name = rb_id2name(id);
 		visibility = ce->flag;
-		rb_warn("already initialized constant %s", rb_id2name(id));
+		rb_warn("already initialized constant %s", name);
+		if (!NIL_P(ce->file) && ce->line) {
+		    rb_compile_warn(RSTRING_PTR(ce->file), ce->line,
+				    "previous definition of %s was here", name);
+		}
 	    }
 	}
     }
@@ -2068,6 +2073,8 @@ rb_const_set(VALUE klass, ID id, VALUE val)
     ce = ALLOC(rb_const_entry_t);
     ce->flag = (rb_const_flag_t)visibility;
     ce->value = val;
+    ce->file = rb_sourcefilename();
+    ce->line = rb_sourceline();
 
     st_insert(RCLASS_CONST_TBL(klass), (st_data_t)id, (st_data_t)ce);
 }

vm.c

@@ -829,6 +829,20 @@ vm_backtrace(rb_thread_t *th, int lev)
     return rb_ary_reverse(ary);
 }
 
+VALUE
+rb_sourcefilename(void)
+{
+    rb_thread_t *th = GET_THREAD();
+    rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);
+
+    if (cfp) {
+	return cfp->iseq->filename;
+    }
+    else {
+	return Qnil;
+    }
+}
+
 const char *
 rb_sourcefile(void)
 {