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Re: [RFC][Python] gdbpy_frame_stop_reason_string bug
On Wednesday 12 October 2011 15:02:20, Kevin Pouget wrote:
> I wanted to discuss the best way to solve this bug before going any
> further in the development:
>
> > (gdb) py print gdb.frame_stop_reason_string(2)
> > /home/kevin/travail/git/gdb/gdb/frame.c:2372: internal-error: Invalid frame stop reason
> > A problem internal to GDB has been detected,further debugging may prove unreliable.
>
>
> I prepared the attached patch, which requires to change
> 'internal_error' to a simple 'error' (I assume that it can't break
> anything because it ends up calling `exit()', but I didn't check yet),
>
> but "Frame.unwind_stop_reason ()" easily returns 'invalid frame stop
> reason', for instance
2 == UNWIND_OUTERMOST. Why would that be invalid?
frame_stop_reason_string isn't handling this, nor UNWIND_NO_REASON.
Is there a reason for that? I think something like the below
patch would be much better. This _is_ an internal error / bug after
all. (We could leave UNWIND_FIRST_ERROR as part of the enum with
`UNWIND_UNAVAILABLE = UNWIND_FIRST_ERROR', I don't have that
a strong preference.) Better yet could be to define the
values/strings in the same place in a .def file.
Where do magical the numbers come from? I hope we've not
blessed them as stable.
--
Pedro Alves
---
gdb/frame.c | 8 ++++++--
gdb/frame.h | 4 +++-
gdb/python/py-frame.c | 2 +-
gdb/stack.c | 2 +-
4 files changed, 11 insertions(+), 5 deletions(-)
Index: src/gdb/frame.c
===================================================================
--- src.orig/gdb/frame.c 2011-10-11 12:43:17.000000000 +0100
+++ src/gdb/frame.c 2011-10-12 15:40:21.593658382 +0100
@@ -2351,9 +2351,15 @@ frame_stop_reason_string (enum unwind_st
{
switch (reason)
{
+ case UNWIND_NO_REASON:
+ return _("no reason");
+
case UNWIND_NULL_ID:
return _("unwinder did not report frame ID");
+ case UNWIND_OUTERMOST:
+ return _("outermost");
+
case UNWIND_UNAVAILABLE:
return _("Not enough registers or memory available to unwind further");
@@ -2366,8 +2372,6 @@ frame_stop_reason_string (enum unwind_st
case UNWIND_NO_SAVED_PC:
return _("frame did not save the PC");
- case UNWIND_NO_REASON:
- case UNWIND_FIRST_ERROR:
default:
internal_error (__FILE__, __LINE__,
"Invalid frame stop reason");
Index: src/gdb/frame.h
===================================================================
--- src.orig/gdb/frame.h 2011-10-11 12:43:17.000000000 +0100
+++ src/gdb/frame.h 2011-10-12 15:42:14.303658362 +0100
@@ -466,7 +466,7 @@ enum unwind_stop_reason
abnormal stack termination. If a backtrace stops for one
of these reasons, we'll let the user know. This marker
is not a valid stop reason. */
- UNWIND_FIRST_ERROR,
+#define UNWIND_FIRST_ERROR UNWIND_UNAVAILABLE
/* Can't unwind further, because that would require knowing the
values of registers or memory that haven't been collected. */
@@ -487,6 +487,8 @@ enum unwind_stop_reason
/* The frame unwinder didn't find any saved PC, but we needed
one to unwind further. */
UNWIND_NO_SAVED_PC,
+
+#define UNWIND_STOP_REASON_LAST UNWIND_NO_SAVED_PC
};
/* Return the reason why we can't unwind past this frame. */
Index: src/gdb/stack.c
===================================================================
--- src.orig/gdb/stack.c 2011-10-11 12:43:20.000000000 +0100
+++ src/gdb/stack.c 2011-10-12 15:38:23.083658404 +0100
@@ -1625,7 +1625,7 @@ backtrace_command_1 (char *count_exp, in
enum unwind_stop_reason reason;
reason = get_frame_unwind_stop_reason (trailing);
- if (reason > UNWIND_FIRST_ERROR)
+ if (reason >= UNWIND_FIRST_ERROR)
printf_filtered (_("Backtrace stopped: %s\n"),
frame_stop_reason_string (reason));
}
Index: src/gdb/python/py-frame.c
===================================================================
--- src.orig/gdb/python/py-frame.c 2011-10-12 15:50:30.000000000 +0100
+++ src/gdb/python/py-frame.c 2011-10-12 15:50:36.583658269 +0100
@@ -542,7 +542,7 @@ gdbpy_frame_stop_reason_string (PyObject
if (!PyArg_ParseTuple (args, "i", &reason))
return NULL;
- if (reason < 0 || reason > UNWIND_NO_SAVED_PC)
+ if (reason < 0 || reason > UNWIND_STOP_REASON_LAST)
{
PyErr_SetString (PyExc_ValueError,
_("Invalid frame stop reason."));