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Re: [RFA] Make "bt N" print correct number of frames when using a frame filter
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Tom Tromey <tom at tromey dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Tue, 25 Apr 2017 14:27:31 -0400
- Subject: Re: [RFA] Make "bt N" print correct number of frames when using a frame filter
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- References: <20170423160446.17062-1-tom@tromey.com>
Thanks for the patch, Tom.
On Sunday, April 23 2017, Tom Tromey wrote:
> PR python/16497 notes that using "bt" with a positive argument prints
> the wrong number of frames when a frame filter is in use. Also, in this
> case, the non-frame-filter path will print a message about "More stack
> frames" when there are more; but this is not done in the frame-filter
> case.
>
> The first problem is that backtrace_command_1 passes the wrong value
> to apply_ext_lang_frame_filter -- that function takes the final
> frame's number as an argument, but backtrace_command_1 passes the
> count, which is off by one.
>
> The solution to the second problem is to have the C stack-printing
> code stop at the correct number of frames and then print the message.
>
> Tested using the buildbot.
>
> ChangeLog
> 2017-04-22 Tom Tromey <tom@tromey.com>
>
> PR python/16497:
> * stack.c (backtrace_command_1): Set PRINT_MORE_FRAMES flag. Fix
> off-by-one in py_end computation.
> * python/py-framefilter.c (gdbpy_apply_frame_filter): Handle
> PRINT_MORE_FRAMES.
> * extension.h (enum frame_filter_flags) <PRINT_MORE_FRAMES>: New
> constant.
>
> testsuite/ChangeLog
> 2017-04-22 Tom Tromey <tom@tromey.com>
>
> PR python/16497:
> * gdb.python/py-framefilter.exp: Update test.
> ---
> gdb/ChangeLog | 10 ++++++++++
> gdb/extension.h | 3 +++
> gdb/python/py-framefilter.c | 25 +++++++++++++++++++++++++
> gdb/stack.c | 6 +++++-
> gdb/testsuite/ChangeLog | 5 +++++
> gdb/testsuite/gdb.python/py-framefilter.exp | 2 +-
> 6 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 28ae0a7..85d5da5 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,5 +1,15 @@
> 2017-04-22 Tom Tromey <tom@tromey.com>
>
> + PR python/16497:
> + * stack.c (backtrace_command_1): Set PRINT_MORE_FRAMES flag. Fix
> + off-by-one in py_end computation.
> + * python/py-framefilter.c (gdbpy_apply_frame_filter): Handle
> + PRINT_MORE_FRAMES.
> + * extension.h (enum frame_filter_flags) <PRINT_MORE_FRAMES>: New
> + constant.
> +
> +2017-04-22 Tom Tromey <tom@tromey.com>
> +
> * mi/mi-cmd-file.c (mi_cmd_file_list_shared_libraries): Use
> ui_out_emit_list.
> * stack.c (print_frame): Use ui_out_emit_list.
> diff --git a/gdb/extension.h b/gdb/extension.h
> index 2c79411..cda2ebf 100644
> --- a/gdb/extension.h
> +++ b/gdb/extension.h
> @@ -100,6 +100,9 @@ enum frame_filter_flags
>
> /* Set this flag if frame locals are to be printed. */
> PRINT_LOCALS = 8,
> +
> + /* Set this flag if a "More frames" message is to be printed. */
> + PRINT_MORE_FRAMES = 16,
> };
Not that I want you to fix this, but I like when bitflags are set using
the "1 << X" notation. Oh, well...
>
> /* A choice of the different frame argument printing strategies that
> diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
> index 75b055c..b604d51 100644
> --- a/gdb/python/py-framefilter.c
> +++ b/gdb/python/py-framefilter.c
> @@ -1355,6 +1355,18 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
>
> gdbpy_enter enter_py (gdbarch, current_language);
>
> + /* When we're limiting the number of frames, be careful to request
> + one extra frame, so that we can print a message if there are more
> + frames. */
> + int frame_countdown = -1;
> + if ((flags & PRINT_MORE_FRAMES) != 0 && frame_low >= 0 && frame_high >= 0)
> + {
> + ++frame_high;
> + /* This has an extra +1 because it is checked before a frame is
> + printed. */
> + frame_countdown = frame_high - frame_low + 1;
> + }
> +
> gdbpy_ref<> iterable (bootstrap_python_frame_filters (frame, frame_low,
> frame_high));
>
> @@ -1402,6 +1414,19 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
> break;
> }
>
> + if (frame_countdown != -1)
> + {
> + assert ((flags & PRINT_MORE_FRAMES) != 0);
gdb_assert here, right?
> + --frame_countdown;
> + if (frame_countdown == 0)
> + {
> + /* We've printed all the frames we were asked to
> + print, but more frames existed. */
> + printf_filtered (_("(More stack frames follow...)\n"));
> + break;
> + }
> + }
> +
> success = py_print_frame (item.get (), flags, args_type, out, 0,
> levels_printed.get ());
>
> diff --git a/gdb/stack.c b/gdb/stack.c
> index 7f8a51c..37e8767 100644
> --- a/gdb/stack.c
> +++ b/gdb/stack.c
> @@ -1766,7 +1766,9 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
> else
> {
> py_start = 0;
> - py_end = count;
> + /* The argument to apply_ext_lang_frame_filter is the number
> + of the final frame to print, and frames start at 0. */
> + py_end = count - 1;
> }
> }
> else
> @@ -1800,6 +1802,8 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
>
> if (show_locals)
> flags |= PRINT_LOCALS;
> + if (from_tty)
> + flags |= PRINT_MORE_FRAMES;
>
> if (!strcmp (print_frame_arguments, "scalars"))
> arg_type = CLI_SCALAR_VALUES;
> diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
> index c4d5b79..df883da 100644
> --- a/gdb/testsuite/ChangeLog
> +++ b/gdb/testsuite/ChangeLog
> @@ -1,3 +1,8 @@
> +2017-04-22 Tom Tromey <tom@tromey.com>
> +
> + PR python/16497:
> + * gdb.python/py-framefilter.exp: Update test.
> +
> 2017-04-19 Pedro Alves <palves@redhat.com>
>
> * gdb.threads/threadapply.exp (kill_and_remove_inferior): New
> diff --git a/gdb/testsuite/gdb.python/py-framefilter.exp b/gdb/testsuite/gdb.python/py-framefilter.exp
> index bbec48d..d81d144 100644
> --- a/gdb/testsuite/gdb.python/py-framefilter.exp
> +++ b/gdb/testsuite/gdb.python/py-framefilter.exp
> @@ -149,7 +149,7 @@ gdb_test "bt -2" \
> ".*#26.*func5.*#27.*in main \\(\\).*" \
> "bt -2 with frame-filter Reverse disabled"
> gdb_test "bt 3" \
> - ".*#0.*end_func.*#1.*in funca \\(\\).*#2.*in funcb \\(j=10\\).*" \
> + ".*#0.*end_func.*#1.*in funca \\(\\).*#2.*in funcb \\(j=10\\)\[^#\]*More stack frames follow.*" \
> "bt 3 with frame-filter Reverse disabled"
> gdb_test "bt no-filter full" \
> ".*#0.*end_func.*str = $hex \"The End\".*st2 = $hex \"Is Near\".*b = 12.*c = 5.*#1.*in funca \\(\\).*#2.*in funcb \\(j=10\\).*bar = \{a = 42, b = 84\}.*" \
> --
> 2.9.3
Otherwise, LGTM.
Thanks,
--
Sergio
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