From e9786a4eef01cbc6ed44e715b898c694bc380152 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sun, 13 Nov 2016 05:25:54 +0000
Subject: error.c: redefined backtrace

* error.c (rb_get_backtrace): honor redefined Exception#backtrace
  method.  [ruby-core:78097] [Bug #12925]

* eval.c (setup_exception): rescue exceptions during backtrace
  setup.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56767 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 error.c                     | 23 +++++++++++++----------
 eval.c                      | 25 +++++++++++++++++++------
 test/ruby/test_exception.rb | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 16 deletions(-)

diff --git a/error.c b/error.c
index 4503742896..e03a4eea39 100644
--- a/error.c
+++ b/error.c
@@ -885,17 +885,20 @@ exc_backtrace(VALUE exc)
 VALUE
 rb_get_backtrace(VALUE exc)
 {
-    VALUE info, klass = rb_eException;
     ID mid = id_backtrace;
-    rb_thread_t *th = GET_THREAD();
-    if (NIL_P(exc))
-	return Qnil;
-    EXEC_EVENT_HOOK(th, RUBY_EVENT_C_CALL, exc, mid, mid, klass, Qundef);
-    info = exc_backtrace(exc);
-    EXEC_EVENT_HOOK(th, RUBY_EVENT_C_RETURN, exc, mid, mid, klass, info);
-    if (NIL_P(info))
-	return Qnil;
-    return rb_check_backtrace(info);
+    if (rb_method_basic_definition_p(CLASS_OF(exc), id_backtrace)) {
+	VALUE info, klass = rb_eException;
+	rb_thread_t *th = GET_THREAD();
+	if (NIL_P(exc))
+	    return Qnil;
+	EXEC_EVENT_HOOK(th, RUBY_EVENT_C_CALL, exc, mid, mid, klass, Qundef);
+	info = exc_backtrace(exc);
+	EXEC_EVENT_HOOK(th, RUBY_EVENT_C_RETURN, exc, mid, mid, klass, info);
+	if (NIL_P(info))
+	    return Qnil;
+	return rb_check_backtrace(info);
+    }
+    return rb_funcall(exc, mid, 0, 0);
 }
 
 /*
diff --git a/eval.c b/eval.c
index 865dc8c8e0..6b4acf575d 100644
--- a/eval.c
+++ b/eval.c
@@ -507,13 +507,25 @@ setup_exception(rb_thread_t *th, int tag, volatile VALUE mesg, VALUE cause)
 		rb_ivar_set(mesg, idBt_locations, at);
 	    }
 	}
-	else if (NIL_P(rb_get_backtrace(mesg))) {
-	    at = rb_vm_backtrace_object();
-	    if (OBJ_FROZEN(mesg)) {
-		mesg = rb_obj_dup(mesg);
+	else {
+	    int status;
+
+	    TH_PUSH_TAG(th);
+	    if ((status = EXEC_TAG()) == 0) {
+		VALUE bt;
+		if (rb_threadptr_set_raised(th)) goto fatal;
+		bt = rb_get_backtrace(mesg);
+		if (NIL_P(bt)) {
+		    at = rb_vm_backtrace_object();
+		    if (OBJ_FROZEN(mesg)) {
+			mesg = rb_obj_dup(mesg);
+		    }
+		    rb_ivar_set(mesg, idBt_locations, at);
+		    set_backtrace(mesg, at);
+		}
+		rb_threadptr_reset_raised(th);
 	    }
-	    rb_ivar_set(mesg, idBt_locations, at);
-	    set_backtrace(mesg, at);
+	    TH_POP_TAG();
 	}
     }
 
@@ -556,6 +568,7 @@ setup_exception(rb_thread_t *th, int tag, volatile VALUE mesg, VALUE cause)
     }
 
     if (rb_threadptr_set_raised(th)) {
+      fatal:
 	th->errinfo = exception_error;
 	rb_threadptr_reset_raised(th);
 	TH_JUMP_TAG(th, TAG_FATAL);
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index 32918df16d..b397d76d3e 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -965,4 +965,38 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
       }
     end;
   end
+
+  def test_redefined_backtrace
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    begin;
+      $exc = nil
+
+      class Exception
+        undef backtrace
+        def backtrace
+          $exc = self
+        end
+      end
+
+      e = assert_raise(RuntimeError) {
+        raise RuntimeError, "hello"
+      }
+      assert_same(e, $exc)
+    end;
+  end
+
+  def test_wrong_backtrace
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    begin;
+      class Exception
+        undef backtrace
+        def backtrace(a)
+        end
+      end
+
+      assert_raise(RuntimeError) {
+        raise RuntimeError, "hello"
+      }
+    end;
+  end
 end
-- 
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