fix erroneous error-handling in frame filter code

This fixes PR python/16487.

The bug here is that the function-name-handling code in py_print_frame
had a small logic error (really a misplaced closing brace).  This
error could lead to a Py_DECREF(NULL), which crashes.

This patch fixes the bug in the obvious way.

Built and regtested on x86-64 Fedora 18.  New test case included.

2014-01-23  Tom Tromey  <tromey@redhat.com>

	PR python/16487:
	* python/py-framefilter.c (py_print_frame): Don't call Py_DECREF
	on a NULL pointer.  Move "goto error" to correct place.

2014-01-23  Tom Tromey  <tromey@redhat.com>

	PR python/16487:
	* gdb.python/py-framefilter.exp: Add test using "Error" filter.
	* gdb.python/py-framefilter.py (ErrorInName, ErrorFilter): New
	classes.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2014-01-23  Tom Tromey  <tromey@redhat.com>
+
+	PR python/16487:
+	* python/py-framefilter.c (py_print_frame): Don't call Py_DECREF
+	on a NULL pointer.  Move "goto error" to correct place.
+
 2014-01-23  Tom Tromey  <tromey@redhat.com>
 
 	PR python/16491:

gdb/python/py-framefilter.c

@@ -1218,12 +1218,12 @@ py_print_frame (PyObject *filter, int flags, enum py_frame_args args_type,
 		  gdbpy_convert_exception (except);
 		  goto error;
 		}
-	    }
 	      Py_DECREF (py_func);
 	    }
 	  else
 	    goto error;
 	}
+    }
 
 
   /* Frame arguments.  Check the result, and error if something went

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2014-01-23  Tom Tromey  <tromey@redhat.com>
+
+	PR python/16487:
+	* gdb.python/py-framefilter.exp: Add test using "Error" filter.
+	* gdb.python/py-framefilter.py (ErrorInName, ErrorFilter): New
+	classes.
+
 2014-01-23  Tom Tromey  <tromey@redhat.com>
 
 	PR python/16491:

gdb/testsuite/gdb.python/py-framefilter.exp

@@ -177,6 +177,17 @@ gdb_test "bt 1" \
     "#0  end_func \\(foo=21, bar=\"Param\", fb=, bf=\{nothing = \"Foo Bar\", f = 42, s = 19\}\\) at .*py-framefilter.c.*" \
     "bt 1 no addresss"
 
+gdb_test_no_output "set python print-stack message" \
+    "Set python print-stack to message for Error filter"
+gdb_test_no_output  "enable frame-filter global Error" \
+    "enable frame-filter global Error"
+set test "bt 1 with Error filter"
+gdb_test_multiple "bt 1" $test {
+    -re "Python Exception .*whoops:.*$gdb_prompt $" {
+	pass $test
+    }
+}
+
 remote_file host delete ${remote_python_file}
 
 # Test with no debuginfo

gdb/testsuite/gdb.python/py-framefilter.py

@@ -128,5 +128,25 @@ class FrameElider ():
     def filter (self, frame_iter):
         return ElidingIterator (frame_iter)
 
+# A simple decorator that gives an error when computing the function.
+class ErrorInName(FrameDecorator):
+    def __init__(self, frame):
+        FrameDecorator.__init__(self, frame)
+
+    def function(self):
+        raise RuntimeError('whoops')
+
+# A filter that supplies buggy frames.  Disabled by default.
+class ErrorFilter():
+    def __init__ (self):
+        self.name = "Error"
+        self.priority = 1
+        self.enabled = False
+        gdb.frame_filters [self.name] = self
+
+    def filter(self, frame_iter):
+        return itertools.imap(ErrorInName, frame_iter)
+
 FrameFilter()
 FrameElider()
+ErrorFilter()