[RFA v2 00/13] various frame filter fixes and cleanups

[RFA v2 00/13] various frame filter fixes and cleanups

[Tom Tromey]

Here's version 2 of one my frame-filter-related patch series.  This
series rationalizes backtrace command-line parsing, fixes a few bugs,
and adds the ability to not print "elided" frames.

Reviews of v1 mostly were in June, e.g.:
https://sourceware.org/ml/gdb-patches/2017-06/msg00741.html
The series was posted here:
https://sourceware.org/ml/gdb-patches/2017-04/msg00671.html

I believe this new series addresses all the review comments.  However,
there have been changes and additions, so you will probably want to
re-read everything, and especially the new final patch.

There were a few questions last time.  Some are answered in specific
patches, but for the others:

[ about exceptions in py-framefilter.c ]

> Are any of these returning back to the Python runtime?  If so, then
> we can't let C++ exceptions cross it.

I think the answer is no.

> So "bt elide" means "elide the elided frames", not "show me the
> elided frames too".  It's fine with me, though I mildly wonder whether
> users will be confused by the "double negative".

"Elide" means "drop", so really "bt elide" should mean "drop whatever
frames are droppable".  Having "bt elide" mean "show the dropped
frames" would be confusing.  But maybe another word would be better
here, I don't know.

Tom

[RFA v2 11/13] Improve "backtrace" help text

[Tom Tromey]

This improves help text in stack.c in two ways.  First, it removes
trailing newlines from various help strings.  I think these are never
needed.  Second, it adds a "Usage" line to the "backtrace" text, as
suggested by Pedro.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* stack.c (_initialize_stack): Remove trailing newlines from help
	text.  Add "Usage" line to "backtrace" help.
---
 gdb/ChangeLog |  5 +++++
 gdb/stack.c   | 13 +++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9af53f8..84df331 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* stack.c (_initialize_stack): Remove trailing newlines from help
+	text.  Add "Usage" line to "backtrace" help.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	PR python/16486:
 	* python/py-framefilter.c (py_print_args): Call wrap_hint.
 
diff --git a/gdb/stack.c b/gdb/stack.c
index 94f24b2..20cdd97 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -2585,22 +2585,23 @@ This is useful in command scripts."));
 Select and print a stack frame.\nWith no argument, \
 print the selected stack frame.  (See also \"info frame\").\n\
 An argument specifies the frame to select.\n\
-It can be a stack frame number or the address of the frame.\n"));
+It can be a stack frame number or the address of the frame."));
 
   add_com_alias ("f", "frame", class_stack, 1);
 
   add_com_suppress_notification ("select-frame", class_stack, select_frame_command, _("\
 Select a stack frame without printing anything.\n\
 An argument specifies the frame to select.\n\
-It can be a stack frame number or the address of the frame.\n"),
+It can be a stack frame number or the address of the frame."),
 		 &cli_suppress_notification.user_selected_context);
 
   add_com ("backtrace", class_stack, backtrace_command, _("\
 Print backtrace of all stack frames, or innermost COUNT frames.\n\
-With a negative argument, print outermost -COUNT frames.\nUse of the \
-'full' qualifier also prints the values of the local variables.\n\
+Usage: backtrace [QUALIFIERS]... [COUNT]\n\
+With a negative argument, print outermost -COUNT frames.\n\
+Use of the 'full' qualifier also prints the values of the local variables.\n\
 Use of the 'no-filters' qualifier prohibits frame filters from executing\n\
-on this backtrace.\n"));
+on this backtrace."));
   add_com_alias ("bt", "backtrace", class_stack, 0);
 
   add_com_alias ("where", "backtrace", class_alias, 0);
@@ -2618,7 +2619,7 @@ on this backtrace.\n"));
   if (dbx_commands)
     add_com ("func", class_stack, func_command, _("\
 Select the stack frame that contains <func>.\n\
-Usage: func <name>\n"));
+Usage: func <name>"));
 
   add_setshow_enum_cmd ("frame-arguments", class_stack,
 			print_frame_arguments_choices, &print_frame_arguments,
-- 
2.9.4

Re: [RFA v2 11/13] Improve "backtrace" help text

[Pedro Alves]

On 08/14/2017 04:40 AM, Tom Tromey wrote:
> +Usage: backtrace [QUALIFIERS]... [COUNT]\n\

QUALIFIER, singular.   "..." already implies multiple instances.

Thanks,
Pedro Alves

Re: [RFA v2 11/13] Improve "backtrace" help text

[Tom Tromey]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> On 08/14/2017 04:40 AM, Tom Tromey wrote:
>> +Usage: backtrace [QUALIFIERS]... [COUNT]\n\

Pedro> QUALIFIER, singular.   "..." already implies multiple instances.

I've fixed this locally.

Tom

Re: [RFA v2 11/13] Improve "backtrace" help text

[Pedro Alves]

On 08/14/2017 03:34 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> 
> Pedro> On 08/14/2017 04:40 AM, Tom Tromey wrote:
>>> +Usage: backtrace [QUALIFIERS]... [COUNT]\n\
> 
> Pedro> QUALIFIER, singular.   "..." already implies multiple instances.
> 
> I've fixed this locally.
> 

It's OK with that nice addressed.  Please push.  Sorry for not
being explicit.

Thanks,
Pedro Alves

Re: [RFA v2 11/13] Improve "backtrace" help text

[Tom Tromey]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> It's OK with that nice addressed.  Please push.  Sorry for not
Pedro> being explicit.

It's no trouble.  I am not going to push right away because I still
haven't really considered the points you raise in the email about the
"elide" naming decision.

Tom

[RFA v2 13/13] Remove verbose code from backtrace command

[Tom Tromey]

In https://sourceware.org/ml/gdb-patches/2017-06/msg00741.html,
Pedro asks:

> Doesn't the "info verbose on" bit affect frame filters too?

The answer is that yes, it could.  However, it's not completely
effective, because the C code can't guess how many frames might need
to be unwound to satisfy the request -- a frame filter will request as
many frames as it needs.

Also, I tried removing this code from backtrace, and I think the
result is better without it.  In particular, now the expansion line
occurs just before the frame that caused the expansion, like:

    (gdb) bt no-filters
    #0  0x00007ffff576cecd in poll () from /lib64/libc.so.6
    Reading in symbols for ../../binutils-gdb/gdb/event-loop.c...done.
    #1  0x00000000007ecc33 in gdb_wait_for_event (block=1)
	at ../../binutils-gdb/gdb/event-loop.c:772
    #2  0x00000000007ec006 in gdb_do_one_event ()
	at ../../binutils-gdb/gdb/event-loop.c:347
    #3  0x00000000007ec03e in start_event_loop ()
	at ../../binutils-gdb/gdb/event-loop.c:371
    Reading in symbols for ../../binutils-gdb/gdb/main.c...done.
    #4  0x000000000086693d in captured_command_loop (
	Reading in symbols for ../../binutils-gdb/gdb/exceptions.c...done.
    data=0x0) at ../../binutils-gdb/gdb/main.c:325

So, I am proposing this patch to simply remove this code.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* stack.c (backtrace_command_1): Remove verbose code.
---
 gdb/ChangeLog |  4 ++++
 gdb/stack.c   | 18 ------------------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0ed62ce..f621822 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,9 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* stack.c (backtrace_command_1): Remove verbose code.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* python/py-framefilter.c (py_print_type): Don't catch
 	exceptions.  Return void.
 	(py_print_value): Likewise.
diff --git a/gdb/stack.c b/gdb/stack.c
index 20cdd97..8ba2239 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1798,24 +1798,6 @@ backtrace_command_1 (char *count_exp, int flags, int no_filters,
 	  count = -1;
 	}
 
-      if (info_verbose)
-	{
-	  /* Read in symbols for all of the frames.  Need to do this in a
-	     separate pass so that "Reading in symbols for xxx" messages
-	     don't screw up the appearance of the backtrace.  Also if
-	     people have strong opinions against reading symbols for
-	     backtrace this may have to be an option.  */
-	  i = count;
-	  for (fi = trailing; fi != NULL && i--; fi = get_prev_frame (fi))
-	    {
-	      CORE_ADDR pc;
-
-	      QUIT;
-	      pc = get_frame_address_in_block (fi);
-	      expand_symtab_containing_pc (pc, find_pc_mapped_section (pc));
-	    }
-	}
-
       for (i = 0, fi = trailing; fi && count--; i++, fi = get_prev_frame (fi))
 	{
 	  QUIT;
-- 
2.9.4

Re: [RFA v2 13/13] Remove verbose code from backtrace command

[Pedro Alves]

On 08/14/2017 04:40 AM, Tom Tromey wrote:
> In https://sourceware.org/ml/gdb-patches/2017-06/msg00741.html,
> Pedro asks:
> 
>> Doesn't the "info verbose on" bit affect frame filters too?
> 
> The answer is that yes, it could.  However, it's not completely
> effective, because the C code can't guess how many frames might need
> to be unwound to satisfy the request -- a frame filter will request as
> many frames as it needs.
> 
> Also, I tried removing this code from backtrace, and I think the
> result is better without it.  In particular, now the expansion line
> occurs just before the frame that caused the expansion, like:
> 
>     (gdb) bt no-filters
>     #0  0x00007ffff576cecd in poll () from /lib64/libc.so.6
>     Reading in symbols for ../../binutils-gdb/gdb/event-loop.c...done.
>     #1  0x00000000007ecc33 in gdb_wait_for_event (block=1)
> 	at ../../binutils-gdb/gdb/event-loop.c:772
>     #2  0x00000000007ec006 in gdb_do_one_event ()
> 	at ../../binutils-gdb/gdb/event-loop.c:347
>     #3  0x00000000007ec03e in start_event_loop ()
> 	at ../../binutils-gdb/gdb/event-loop.c:371
>     Reading in symbols for ../../binutils-gdb/gdb/main.c...done.
>     #4  0x000000000086693d in captured_command_loop (
> 	Reading in symbols for ../../binutils-gdb/gdb/exceptions.c...done.
>     data=0x0) at ../../binutils-gdb/gdb/main.c:325
> 
> So, I am proposing this patch to simply remove this code.
> 
> ChangeLog
> 2017-08-13  Tom Tromey  <tom@tromey.com>
> 
> 	* stack.c (backtrace_command_1): Remove verbose code.

This is fine with me.

Thanks,
Pedro Alves

[RFA v2 09/13] Return EXT_LANG_BT_ERROR in one more spot in py-framefilter.c

[Tom Tromey]

While reading py-framefilter.c, I found one spot where an exception
could be caught but then not be turned into EXT_LANG_BT_ERROR.  This
patch fixes this spot.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (py_print_single_arg): Return
	EXT_LANG_BT_ERROR from catch.
---
 gdb/ChangeLog               | 5 +++++
 gdb/python/py-framefilter.c | 1 +
 2 files changed, 6 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 630e27b..e5aeb22 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* python/py-framefilter.c (py_print_single_arg): Return
+	EXT_LANG_BT_ERROR from catch.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	PR backtrace/15584:
 	* stack.c (backtrace_command_1): Move some code into no-filters
 	"if".
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 76e637c..73f2a31 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -457,6 +457,7 @@ py_print_single_arg (struct ui_out *out,
   CATCH (except, RETURN_MASK_ERROR)
     {
       gdbpy_convert_exception (except);
+      retval = EXT_LANG_BT_ERROR;
     }
   END_CATCH
 
-- 
2.9.4

[RFA v2 07/13] Throw a "quit" on a KeyboardException in py-framefilter.c

[Tom Tromey]

If a C-c comes while the Python code for a frame filter is running, it
will be turned into a Python KeyboardException.  It seems good for
this to be treated like a GDB quit, so this patch changes
py-framefilter.c to notice this situation and call throw_quit in this
case.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (throw_quit_or_print_exception): New
	function.
	(gdbpy_apply_frame_filter): Use it.

testsuite/ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* gdb.python/py-framefilter.exp: Add test for KeyboardInterrupt.
	* gdb.python/py-framefilter.py (name_error): New global.
	(ErrorInName.function): Use name_error.
---
 gdb/ChangeLog                               |  6 ++++++
 gdb/python/py-framefilter.c                 | 21 ++++++++++++++++++---
 gdb/testsuite/ChangeLog                     |  6 ++++++
 gdb/testsuite/gdb.python/py-framefilter.exp | 10 ++++++++++
 gdb/testsuite/gdb.python/py-framefilter.py  |  6 +++++-
 5 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 825c099..33db802 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* python/py-framefilter.c (throw_quit_or_print_exception): New
+	function.
+	(gdbpy_apply_frame_filter): Use it.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	PR cli/17716:
 	* python/py-framefilter.c (py_print_type, py_print_value)
 	(enumerate_args, py_print_args, gdbpy_apply_frame_filter): Use
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index e0a7bd0..76e637c 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -1305,6 +1305,21 @@ bootstrap_python_frame_filters (struct frame_info *frame,
     return iterable.release ();
 }
 
+/* A helper function that will either print an exception or, if it is
+   a KeyboardException, throw a quit.  This can only be called when
+   the Python exception is set.  */
+
+static void
+throw_quit_or_print_exception ()
+{
+  if (PyErr_ExceptionMatches (PyExc_KeyboardInterrupt))
+    {
+      PyErr_Clear ();
+      throw_quit ("Quit");
+    }
+  gdbpy_print_stack ();
+}
+
 /*  This is the only publicly exported function in this file.  FRAME
     is the source frame to start frame-filter invocation.  FLAGS is an
     integer holding the flags for printing.  The following elements of
@@ -1363,7 +1378,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
 	 initialization error.  This return code will trigger a
 	 default backtrace.  */
 
-      gdbpy_print_stack ();
+      throw_quit_or_print_exception ();
       return EXT_LANG_BT_NO_FILTERS;
     }
 
@@ -1386,7 +1401,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
 	{
 	  if (PyErr_Occurred ())
 	    {
-	      gdbpy_print_stack ();
+	      throw_quit_or_print_exception ();
 	      return EXT_LANG_BT_ERROR;
 	    }
 	  break;
@@ -1398,7 +1413,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
       /* Do not exit on error printing a single frame.  Print the
 	 error and continue with other frames.  */
       if (success == EXT_LANG_BT_ERROR)
-	gdbpy_print_stack ();
+	throw_quit_or_print_exception ();
     }
 
   return success;
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 53006d9..1bef7c6 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,11 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* gdb.python/py-framefilter.exp: Add test for KeyboardInterrupt.
+	* gdb.python/py-framefilter.py (name_error): New global.
+	(ErrorInName.function): Use name_error.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	PR backtrace/15582:
 	* gdb.python/py-framefilter.exp: Add "bt elide" test.
 
diff --git a/gdb/testsuite/gdb.python/py-framefilter.exp b/gdb/testsuite/gdb.python/py-framefilter.exp
index 80aa495..1a0572d 100644
--- a/gdb/testsuite/gdb.python/py-framefilter.exp
+++ b/gdb/testsuite/gdb.python/py-framefilter.exp
@@ -213,6 +213,16 @@ gdb_test_multiple "bt 1" $test {
     }
 }
 
+# Now verify that we can see a quit.
+gdb_test_no_output "python name_error = KeyboardInterrupt" \
+    "Change ErrorFilter to throw KeyboardInterrupt"
+set test "bt 1 with KeyboardInterrupt"
+gdb_test_multiple "bt 1" $test {
+    -re "Quit" {
+	pass $test
+    }
+}
+
 # Test with no debuginfo
 
 # We cannot use prepare_for_testing as we have to set the safe-patch
diff --git a/gdb/testsuite/gdb.python/py-framefilter.py b/gdb/testsuite/gdb.python/py-framefilter.py
index edd0e00..b579ec3 100644
--- a/gdb/testsuite/gdb.python/py-framefilter.py
+++ b/gdb/testsuite/gdb.python/py-framefilter.py
@@ -134,13 +134,17 @@ class FrameElider ():
     def filter (self, frame_iter):
         return ElidingIterator (frame_iter)
 
+# This is here so the test can change the kind of error that is
+# thrown.
+name_error = RuntimeError
+
 # 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')
+        raise name_error('whoops')
 
 # A filter that supplies buggy frames.  Disabled by default.
 class ErrorFilter():
-- 
2.9.4

[RFA v2 01/13] Rationalize "backtrace" command line parsing

[Tom Tromey]

The backtrace command has peculiar command-line parsing.  In
particular, it splits the command line, then loops over the arguments.
If it sees a word it recognizes, like "full", it effectively drops
this word from the argument vector.  Then, it pastes together the
remaining arguments, passing them on to backtrace_command_1, which in
turn passes the resulting string to parse_and_eval_long.

The documentation doesn't mention the parse_and_eval_long at all, so
it is a bit of a hidden feature that you can "bt 3*2".  The strange
algorithm above also means you can "bt 3 * no-filters 2" and get 6
frames...

This patch changes backtrace's command line parsing to be a bit more
rational.  Now, special words like "full" are only recognized at the
start of the command.

This also updates the documentation to describe the various bt options
individually.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* stack.c (backtrace_command): Rewrite command line parsing.

doc/ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* gdb.texinfo (Backtrace): Describe options individually.
---
 gdb/ChangeLog       |  4 ++++
 gdb/doc/ChangeLog   |  4 ++++
 gdb/doc/gdb.texinfo | 50 +++++++++++++++------------------------
 gdb/stack.c         | 67 ++++++++++++++++++-----------------------------------
 4 files changed, 49 insertions(+), 76 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c588291..a754b7d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
+	* stack.c (backtrace_command): Rewrite command line parsing.
+
 2017-08-11  Pedro Alves  <palves@redhat.com>
 
 	* infrun.c (process_event_stop_test): Adjust
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 4b40698..2592745 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,7 @@
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
+	* gdb.texinfo (Backtrace): Describe options individually.
+
 2017-08-12  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	PR gdb/21925
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 7528183..bd19d4a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -7200,39 +7200,27 @@ frame (frame zero), followed by its caller (frame one), and on up the
 stack.
 
 @anchor{backtrace-command}
-@table @code
 @kindex backtrace
 @kindex bt @r{(@code{backtrace})}
-@item backtrace
-@itemx bt
-Print a backtrace of the entire stack: one line per frame for all
-frames in the stack.
-
-You can stop the backtrace at any time by typing the system interrupt
-character, normally @kbd{Ctrl-c}.
-
-@item backtrace @var{n}
-@itemx bt @var{n}
-Similar, but print only the innermost @var{n} frames.
-
-@item backtrace -@var{n}
-@itemx bt -@var{n}
-Similar, but print only the outermost @var{n} frames.
-
-@item backtrace full
-@itemx bt full
-@itemx bt full @var{n}
-@itemx bt full -@var{n}
-Print the values of the local variables also.  As described above,
-@var{n} specifies the number of frames to print.
-
-@item backtrace no-filters
-@itemx bt no-filters
-@itemx bt no-filters @var{n}
-@itemx bt no-filters -@var{n}
-@itemx bt no-filters full
-@itemx bt no-filters full @var{n}
-@itemx bt no-filters full -@var{n}
+To print a backtrace of the entire stack, use the @code{backtrace}
+command, or its alias @code{bt}.  This command will print one line per
+frame for all frames in the stack.  You can stop the backtrace at any
+time by typing the system interrupt character, normally @kbd{Ctrl-c}.
+The @code{backtrace} command can accept some arguments:
+
+@table @code
+@item @var{n}
+@itemx @var{n}
+Print only the innermost @var{n} frames.
+
+@item -@var{n}
+@itemx -@var{n}
+Print only the outermost @var{n} frames.
+
+@item full
+Print the values of the local variables also.
+
+@item no-filters
 Do not run Python frame filters on this backtrace.  @xref{Frame
 Filter API}, for more information.  Additionally use @ref{disable
 frame-filter all} to turn off all frame filters.  This is only
diff --git a/gdb/stack.c b/gdb/stack.c
index 3e9dca2..30d16cb 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1868,65 +1868,42 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
 static void
 backtrace_command (char *arg, int from_tty)
 {
-  struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
-  int fulltrace_arg = -1, arglen = 0, argc = 0, no_filters  = -1;
-  int user_arg = 0;
+  bool fulltrace = false;
+  bool filters = true;
 
   if (arg)
     {
-      char **argv;
-      int i;
+      bool done = false;
 
-      gdb_argv built_argv (arg);
-      argv = built_argv.get ();
-      argc = 0;
-      for (i = 0; argv[i]; i++)
+      while (!done)
 	{
 	  unsigned int j;
+	  gdb::unique_xmalloc_ptr<char[]> this_arg (extract_arg (&arg));
 
-	  for (j = 0; j < strlen (argv[i]); j++)
-	    argv[i][j] = TOLOWER (argv[i][j]);
+	  if (this_arg == NULL)
+	    break;
+
+	  for (j = 0; j < strlen (this_arg.get ()); j++)
+	    this_arg[j] = TOLOWER (this_arg[j]);
 
-	  if (no_filters < 0 && subset_compare (argv[i], "no-filters"))
-	    no_filters = argc;
+	  if (subset_compare (this_arg.get (), "no-filters"))
+	    filters = false;
+	  else if (subset_compare (this_arg.get (), "full"))
+	    fulltrace = true;
 	  else
 	    {
-	      if (fulltrace_arg < 0 && subset_compare (argv[i], "full"))
-		fulltrace_arg = argc;
-	      else
-		{
-		  user_arg++;
-		  arglen += strlen (argv[i]);
-		}
+	      /* Not a recognized argument, so stop.  */
+	      done = true;
 	    }
-	  argc++;
 	}
-      arglen += user_arg;
-      if (fulltrace_arg >= 0 || no_filters >= 0)
-	{
-	  if (arglen > 0)
-	    {
-	      arg = (char *) xmalloc (arglen + 1);
-	      make_cleanup (xfree, arg);
-	      arg[0] = 0;
-	      for (i = 0; i < argc; i++)
-		{
-		  if (i != fulltrace_arg && i != no_filters)
-		    {
-		      strcat (arg, argv[i]);
-		      strcat (arg, " ");
-		    }
-		}
-	    }
-	  else
-	    arg = NULL;
-	}
-    }
 
-  backtrace_command_1 (arg, fulltrace_arg >= 0 /* show_locals */,
-		       no_filters >= 0 /* no frame-filters */, from_tty);
+      arg = skip_spaces (arg);
+      if (*arg == '\0')
+	arg = NULL;
+    }
 
-  do_cleanups (old_chain);
+  backtrace_command_1 (arg, fulltrace /* show_locals */,
+		       !filters /* no frame-filters */, from_tty);
 }
 
 /* Iterate over the local variables of a block B, calling CB with
-- 
2.9.4

Re: [RFA v2 01/13] Rationalize "backtrace" command line parsing

[Eli Zaretskii]

> From: Tom Tromey <tom@tromey.com>
> Cc: Tom Tromey <tom@tromey.com>
> Date: Sun, 13 Aug 2017 21:40:18 -0600
> 
> doc/ChangeLog
> 2017-08-13  Tom Tromey  <tom@tromey.com>
> 
> 	* gdb.texinfo (Backtrace): Describe options individually.

Thanks, I have a couple of comments to the documentation part.

> +To print a backtrace of the entire stack, use the @code{backtrace}
> +command, or its alias @code{bt}.  This command will print one line per
> +frame for all frames in the stack.

"All" is only by default, right?

> +The @code{backtrace} command can accept some arguments:
> +
> +@table @code
> +@item @var{n}
> +@itemx @var{n}
> +Print only the innermost @var{n} frames.
> +
> +@item -@var{n}
> +@itemx -@var{n}
> +Print only the outermost @var{n} frames.
> +
> +@item full
> +Print the values of the local variables also.

I think we should say explicitly that "full" and the numbers can be
combined.  Also, I would say somewhere than N is a positive number.

The documentation patch is OK with these minor nits fixed.

[RFA v2 12/13] Simplify exception handling in py-framefilter.c

[Tom Tromey]

This patch changes py-framefilter.c as suggested by Pedro in:
https://sourceware.org/ml/gdb-patches/2017-06/msg00748.html

In particular, gdb exceptions are now caught at the outermost layer,
rather than in each particular function.  This simplifies much of the
code.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (py_print_type): Don't catch
	exceptions.  Return void.
	(py_print_value): Likewise.
	(py_print_single_arg): Likewise.
	(enumerate_args): Don't catch exceptions.
	(py_print_args): Likewise.
	(py_print_frame): Likewise.
	(gdbpy_apply_frame_filter): Catch exceptions here.
---
 gdb/ChangeLog               |  11 +
 gdb/python/py-framefilter.c | 550 +++++++++++++-------------------------------
 2 files changed, 167 insertions(+), 394 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 84df331..0ed62ce 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,16 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* python/py-framefilter.c (py_print_type): Don't catch
+	exceptions.  Return void.
+	(py_print_value): Likewise.
+	(py_print_single_arg): Likewise.
+	(enumerate_args): Don't catch exceptions.
+	(py_print_args): Likewise.
+	(py_print_frame): Likewise.
+	(gdbpy_apply_frame_filter): Catch exceptions here.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* stack.c (_initialize_stack): Remove trailing newlines from help
 	text.  Add "Usage" line to "backtrace" help.
 
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 7114030..85d9d6d 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -199,30 +199,16 @@ mi_should_print (struct symbol *sym, enum mi_print_types type)
 /* Helper function which outputs a type name extracted from VAL to a
    "type" field in the output stream OUT.  OUT is the ui-out structure
    the type name will be output too, and VAL is the value that the
-   type will be extracted from.  Returns EXT_LANG_BT_ERROR on error, with
-   any GDB exceptions converted to a Python exception, or EXT_LANG_BT_OK on
-   success.  */
+   type will be extracted from.  */
 
-static enum ext_lang_bt_status
+static void
 py_print_type (struct ui_out *out, struct value *val)
 {
+  check_typedef (value_type (val));
 
-  TRY
-    {
-      check_typedef (value_type (val));
-
-      string_file stb;
-      type_print (value_type (val), "", &stb, -1);
-      out->field_stream ("type", stb);
-    }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      return EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
-
-  return EXT_LANG_BT_OK;
+  string_file stb;
+  type_print (value_type (val), "", &stb, -1);
+  out->field_stream ("type", stb);
 }
 
 /* Helper function which outputs a value to an output field in a
@@ -230,11 +216,9 @@ py_print_type (struct ui_out *out, struct value *val)
    VAL is the value that will be printed, OPTS contains the value
    printing options, ARGS_TYPE is an enumerator describing the
    argument format, and LANGUAGE is the language_defn that the value
-   will be printed with.  Returns EXT_LANG_BT_ERROR on error, with any GDB
-   exceptions converted to a Python exception, or EXT_LANG_BT_OK on
-   success. */
+   will be printed with.  */
 
-static enum ext_lang_bt_status
+static void
 py_print_value (struct ui_out *out, struct value *val,
 		const struct value_print_options *opts,
 		int indent,
@@ -249,18 +233,7 @@ py_print_value (struct ui_out *out, struct value *val,
   if (args_type == MI_PRINT_SIMPLE_VALUES
       || args_type == MI_PRINT_ALL_VALUES)
     {
-      struct type *type = NULL;
-
-      TRY
-	{
-	  type = check_typedef (value_type (val));
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      struct type *type = check_typedef (value_type (val));
 
       if (args_type == MI_PRINT_ALL_VALUES)
 	should_print = 1;
@@ -275,22 +248,11 @@ py_print_value (struct ui_out *out, struct value *val,
 
   if (should_print)
     {
-      TRY
-	{
-	  string_file stb;
+      string_file stb;
 
-	  common_val_print (val, &stb, indent, opts, language);
-	  out->field_stream ("value", stb);
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      common_val_print (val, &stb, indent, opts, language);
+      out->field_stream ("value", stb);
     }
-
-  return EXT_LANG_BT_OK;
 }
 
 /* Helper function to call a Python method and extract an iterator
@@ -338,10 +300,9 @@ get_py_iter_from_func (PyObject *filter, const char *func)
     ARGS_TYPE is an enumerator describing the argument format,
     PRINT_ARGS_FIELD is a flag which indicates if we output "ARGS=1"
     in MI output in commands where both arguments and locals are
-    printed.  Returns EXT_LANG_BT_ERROR on error, with any GDB exceptions
-    converted to a Python exception, or EXT_LANG_BT_OK on success.  */
+    printed.  */
 
-static enum ext_lang_bt_status
+static void
 py_print_single_arg (struct ui_out *out,
 		     const char *sym_name,
 		     struct frame_arg *fa,
@@ -352,116 +313,97 @@ py_print_single_arg (struct ui_out *out,
 		     const struct language_defn *language)
 {
   struct value *val;
-  enum ext_lang_bt_status retval = EXT_LANG_BT_OK;
 
   if (fa != NULL)
     {
       if (fa->val == NULL && fa->error == NULL)
-	return EXT_LANG_BT_OK;
+	return;
       language = language_def (SYMBOL_LANGUAGE (fa->sym));
       val = fa->val;
     }
   else
     val = fv;
 
-  TRY
-    {
-      gdb::optional<ui_out_emit_tuple> maybe_tuple;
+  gdb::optional<ui_out_emit_tuple> maybe_tuple;
 
-      /*  MI has varying rules for tuples, but generally if there is only
+  /*  MI has varying rules for tuples, but generally if there is only
       one element in each item in the list, do not start a tuple.  The
       exception is -stack-list-variables which emits an ARGS="1" field
       if the value is a frame argument.  This is denoted in this
       function with PRINT_ARGS_FIELD which is flag from the caller to
       emit the ARGS field.  */
-      if (out->is_mi_like_p ())
-	{
-	  if (print_args_field || args_type != NO_VALUES)
-	    maybe_tuple.emplace (out, nullptr);
-	}
+  if (out->is_mi_like_p ())
+    {
+      if (print_args_field || args_type != NO_VALUES)
+	maybe_tuple.emplace (out, nullptr);
+    }
 
-      annotate_arg_begin ();
+  annotate_arg_begin ();
+
+  /* If frame argument is populated, check for entry-values and the
+     entry value options.  */
+  if (fa != NULL)
+    {
+      string_file stb;
 
-      /* If frame argument is populated, check for entry-values and the
-	 entry value options.  */
-      if (fa != NULL)
+      fprintf_symbol_filtered (&stb, SYMBOL_PRINT_NAME (fa->sym),
+			       SYMBOL_LANGUAGE (fa->sym),
+			       DMGL_PARAMS | DMGL_ANSI);
+      if (fa->entry_kind == print_entry_values_compact)
 	{
-	  string_file stb;
+	  stb.puts ("=");
 
 	  fprintf_symbol_filtered (&stb, SYMBOL_PRINT_NAME (fa->sym),
 				   SYMBOL_LANGUAGE (fa->sym),
 				   DMGL_PARAMS | DMGL_ANSI);
-	  if (fa->entry_kind == print_entry_values_compact)
-	    {
-	      stb.puts ("=");
-
-	      fprintf_symbol_filtered (&stb, SYMBOL_PRINT_NAME (fa->sym),
-				       SYMBOL_LANGUAGE (fa->sym),
-				       DMGL_PARAMS | DMGL_ANSI);
-	    }
-	  if (fa->entry_kind == print_entry_values_only
-	      || fa->entry_kind == print_entry_values_compact)
-	    stb.puts ("@entry");
-	  out->field_stream ("name", stb);
 	}
-      else
-	/* Otherwise, just output the name.  */
-	out->field_string ("name", sym_name);
+      if (fa->entry_kind == print_entry_values_only
+	  || fa->entry_kind == print_entry_values_compact)
+	stb.puts ("@entry");
+      out->field_stream ("name", stb);
+    }
+  else
+    /* Otherwise, just output the name.  */
+    out->field_string ("name", sym_name);
 
-      annotate_arg_name_end ();
+  annotate_arg_name_end ();
 
-      if (! out->is_mi_like_p ())
-	out->text ("=");
+  if (! out->is_mi_like_p ())
+    out->text ("=");
 
-      if (print_args_field)
-	out->field_int ("arg", 1);
+  if (print_args_field)
+    out->field_int ("arg", 1);
 
-      /* For MI print the type, but only for simple values.  This seems
-	 weird, but this is how MI choose to format the various output
-	 types.  */
-      if (args_type == MI_PRINT_SIMPLE_VALUES && val != NULL)
-	{
-	  if (py_print_type (out, val) == EXT_LANG_BT_ERROR)
-	    retval = EXT_LANG_BT_ERROR;
-	}
+  /* For MI print the type, but only for simple values.  This seems
+     weird, but this is how MI choose to format the various output
+     types.  */
+  if (args_type == MI_PRINT_SIMPLE_VALUES && val != NULL)
+    py_print_type (out, val);
 
-      if (retval != EXT_LANG_BT_ERROR)
-	{
-	  if (val != NULL)
-	    annotate_arg_value (value_type (val));
+  if (val != NULL)
+    annotate_arg_value (value_type (val));
 
-	  /* If the output is to the CLI, and the user option "set print
-	     frame-arguments" is set to none, just output "...".  */
-	  if (! out->is_mi_like_p () && args_type == NO_VALUES)
-	    out->field_string ("value", "...");
-	  else
+  /* If the output is to the CLI, and the user option "set print
+     frame-arguments" is set to none, just output "...".  */
+  if (! out->is_mi_like_p () && args_type == NO_VALUES)
+    out->field_string ("value", "...");
+  else
+    {
+      /* Otherwise, print the value for both MI and the CLI, except
+	 for the case of MI_PRINT_NO_VALUES.  */
+      if (args_type != NO_VALUES)
+	{
+	  if (val == NULL)
 	    {
-	      /* Otherwise, print the value for both MI and the CLI, except
-		 for the case of MI_PRINT_NO_VALUES.  */
-	      if (args_type != NO_VALUES)
-		{
-		  if (val == NULL)
-		    {
-		      gdb_assert (fa != NULL && fa->error != NULL);
-		      out->field_fmt ("value",
-					_("<error reading variable: %s>"),
-					fa->error);
-		    }
-		  else if (py_print_value (out, val, opts, 0, args_type, language)
-			   == EXT_LANG_BT_ERROR)
-		    retval = EXT_LANG_BT_ERROR;
-		}
+	      gdb_assert (fa != NULL && fa->error != NULL);
+	      out->field_fmt ("value",
+			      _("<error reading variable: %s>"),
+			      fa->error);
 	    }
+	  else
+	    py_print_value (out, val, opts, 0, args_type, language);
 	}
     }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      retval = EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
-
-  return retval;
 }
 
 /* Helper function to loop over frame arguments provided by the
@@ -494,16 +436,7 @@ enumerate_args (PyObject *iter,
 
   opts.deref_ref = 1;
 
-  TRY
-    {
-      annotate_frame_args ();
-    }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      return EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
+  annotate_frame_args ();
 
   /*  Collect the first argument outside of the loop, so output of
       commas in the argument output is correct.  At the end of the
@@ -550,16 +483,7 @@ enumerate_args (PyObject *iter,
 	      return EXT_LANG_BT_ERROR;
 	    }
 
-	  TRY
-	    {
-	      read_frame_arg (sym, frame, &arg, &entryarg);
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
+	  read_frame_arg (sym, frame, &arg, &entryarg);
 
 	  gdb::unique_xmalloc_ptr<char> arg_holder (arg.error);
 	  gdb::unique_xmalloc_ptr<char> entry_holder (entryarg.error);
@@ -570,47 +494,32 @@ enumerate_args (PyObject *iter,
 
 	  if (arg.entry_kind != print_entry_values_only)
 	    {
-	      if (py_print_single_arg (out, NULL, &arg,
-				       NULL, &opts,
-				       args_type,
-				       print_args_field,
-				       NULL) == EXT_LANG_BT_ERROR)
-		return EXT_LANG_BT_ERROR;
+	      py_print_single_arg (out, NULL, &arg,
+				   NULL, &opts,
+				   args_type,
+				   print_args_field,
+				   NULL);
 	    }
 
 	  if (entryarg.entry_kind != print_entry_values_no)
 	    {
 	      if (arg.entry_kind != print_entry_values_only)
 		{
-		  TRY
-		    {
-		      out->text (", ");
-		      out->wrap_hint ("    ");
-		    }
-		  CATCH (except, RETURN_MASK_ERROR)
-		    {
-		      gdbpy_convert_exception (except);
-		      return EXT_LANG_BT_ERROR;
-		    }
-		  END_CATCH
+		  out->text (", ");
+		  out->wrap_hint ("    ");
 		}
 
-	      if (py_print_single_arg (out, NULL, &entryarg, NULL, &opts,
-				       args_type, print_args_field, NULL)
-		  == EXT_LANG_BT_ERROR)
-		return EXT_LANG_BT_ERROR;
+	      py_print_single_arg (out, NULL, &entryarg, NULL, &opts,
+				   args_type, print_args_field, NULL);
 	    }
 	}
       else
 	{
 	  /* If the object has provided a value, we just print that.  */
 	  if (val != NULL)
-	    {
-	      if (py_print_single_arg (out, sym_name.get (), NULL, val, &opts,
-				       args_type, print_args_field,
-				       language) == EXT_LANG_BT_ERROR)
-		return EXT_LANG_BT_ERROR;
-	    }
+	    py_print_single_arg (out, sym_name.get (), NULL, val, &opts,
+				 args_type, print_args_field,
+				 language);
 	}
 
       /* Collect the next item from the iterator.  If
@@ -618,31 +527,11 @@ enumerate_args (PyObject *iter,
 	 comma.  */
       item.reset (PyIter_Next (iter));
       if (item != NULL)
-	{
-	  TRY
-	    {
-	      out->text (", ");
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
-	}
+	out->text (", ");
       else if (PyErr_Occurred ())
 	return EXT_LANG_BT_ERROR;
 
-      TRY
-	{
-	  annotate_arg_end ();
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      annotate_arg_end ();
     }
 
   return EXT_LANG_BT_OK;
@@ -703,18 +592,7 @@ enumerate_locals (PyObject *iter,
 
       /* If the object did not provide a value, read it.  */
       if (val == NULL)
-	{
-	  TRY
-	    {
-	      val = read_var_value (sym, sym_block, frame);
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
-	}
+	val = read_var_value (sym, sym_block, frame);
 
       /* With PRINT_NO_VALUES, MI does not emit a tuple normally as
 	 each output contains only one field.  The exception is
@@ -724,31 +602,19 @@ enumerate_locals (PyObject *iter,
 	  if (print_args_field || args_type != NO_VALUES)
 	    tuple.emplace (out, nullptr);
 	}
-      TRY
+      if (! out->is_mi_like_p ())
 	{
-	  if (! out->is_mi_like_p ())
-	    {
-	      /* If the output is not MI we indent locals.  */
-	      out->spaces (local_indent);
-	    }
+	  /* If the output is not MI we indent locals.  */
+	  out->spaces (local_indent);
+	}
 
-	  out->field_string ("name", sym_name.get ());
+      out->field_string ("name", sym_name.get ());
 
-	  if (! out->is_mi_like_p ())
-	    out->text (" = ");
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      if (! out->is_mi_like_p ())
+	out->text (" = ");
 
       if (args_type == MI_PRINT_SIMPLE_VALUES)
-	{
-	  if (py_print_type (out, val) == EXT_LANG_BT_ERROR)
-	    return EXT_LANG_BT_ERROR;
-	}
+	py_print_type (out, val);
 
       /* CLI always prints values for locals.  MI uses the
 	 simple/no/all system.  */
@@ -756,30 +622,17 @@ enumerate_locals (PyObject *iter,
 	{
 	  int val_indent = (indent + 1) * 4;
 
-	  if (py_print_value (out, val, &opts, val_indent, args_type,
-			      language) == EXT_LANG_BT_ERROR)
-	    return EXT_LANG_BT_ERROR;
+	  py_print_value (out, val, &opts, val_indent, args_type,
+			  language);
 	}
       else
 	{
 	  if (args_type != NO_VALUES)
-	    {
-	      if (py_print_value (out, val, &opts, 0, args_type,
-				  language) == EXT_LANG_BT_ERROR)
-		return EXT_LANG_BT_ERROR;
-	    }
+	    py_print_value (out, val, &opts, 0, args_type,
+			    language);
 	}
 
-      TRY
-	{
-	  out->text ("\n");
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      out->text ("\n");
     }
 
   if (!PyErr_Occurred ())
@@ -862,36 +715,18 @@ py_print_args (PyObject *filter,
 
   ui_out_emit_list list_emitter (out, "args");
 
-  TRY
-    {
-      out->wrap_hint ("   ");
-      annotate_frame_args ();
-      if (! out->is_mi_like_p ())
-	out->text (" (");
-    }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      return EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
+  out->wrap_hint ("   ");
+  annotate_frame_args ();
+  if (! out->is_mi_like_p ())
+    out->text (" (");
 
   if (args_iter != Py_None
       && (enumerate_args (args_iter.get (), out, args_type, 0, frame)
 	  == EXT_LANG_BT_ERROR))
     return EXT_LANG_BT_ERROR;
 
-  TRY
-    {
-      if (! out->is_mi_like_p ())
-	out->text (")");
-    }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      return EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
+  if (! out->is_mi_like_p ())
+    out->text (")");
 
   return EXT_LANG_BT_OK;
 }
@@ -944,16 +779,7 @@ py_print_frame (PyObject *filter, int flags,
   if (frame == NULL)
     return EXT_LANG_BT_ERROR;
 
-  TRY
-    {
-      gdbarch = get_frame_arch (frame);
-    }
-  CATCH (except, RETURN_MASK_ERROR)
-    {
-      gdbpy_convert_exception (except);
-      return EXT_LANG_BT_ERROR;
-    }
-  END_CATCH
+  gdbarch = get_frame_arch (frame);
 
   /* stack-list-variables.  */
   if (print_locals && print_args && ! print_frame_info)
@@ -976,18 +802,7 @@ py_print_frame (PyObject *filter, int flags,
       /* Elided frames are also printed with this function (recursively)
 	 and are printed with indention.  */
       if (indent > 0)
-	{
-	  TRY
-	    {
-	      out->spaces (indent * 4);
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
-	}
+	out->spaces (indent * 4);
 
       /* The address is required for frame annotations, and also for
 	 address printing.  */
@@ -1017,32 +832,24 @@ py_print_frame (PyObject *filter, int flags,
 
       slot = (struct frame_info **) htab_find_slot (levels_printed,
 						    frame, INSERT);
-      TRY
-	{
-	  level = frame_relative_level (frame);
-
-	  /* Check if this frame has already been printed (there are cases
-	     where elided synthetic dummy-frames have to 'borrow' the frame
-	     architecture from the eliding frame.  If that is the case, do
-	     not print 'level', but print spaces.  */
-	  if (*slot == frame)
-	    out->field_skip ("level");
-	  else
-	    {
-	      *slot = frame;
-	      annotate_frame_begin (print_level ? level : 0,
-				    gdbarch, address);
-	      out->text ("#");
-	      out->field_fmt_int (2, ui_left, "level",
-				    level);
-	    }
-	}
-      CATCH (except, RETURN_MASK_ERROR)
+
+      level = frame_relative_level (frame);
+
+      /* Check if this frame has already been printed (there are cases
+	 where elided synthetic dummy-frames have to 'borrow' the frame
+	 architecture from the eliding frame.  If that is the case, do
+	 not print 'level', but print spaces.  */
+      if (*slot == frame)
+	out->field_skip ("level");
+      else
 	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
+	  *slot = frame;
+	  annotate_frame_begin (print_level ? level : 0,
+				gdbarch, address);
+	  out->text ("#");
+	  out->field_fmt_int (2, ui_left, "level",
+			      level);
 	}
-      END_CATCH
     }
 
   if (print_frame_info)
@@ -1051,19 +858,10 @@ py_print_frame (PyObject *filter, int flags,
 	 print nothing.  */
       if (opts.addressprint && has_addr)
 	{
-	  TRY
-	    {
-	      annotate_frame_address ();
-	      out->field_core_addr ("addr", gdbarch, address);
-	      annotate_frame_address_end ();
-	      out->text (" in ");
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
+	  annotate_frame_address ();
+	  out->field_core_addr ("addr", gdbarch, address);
+	  annotate_frame_address_end ();
+	  out->text (" in ");
 	}
 
       /* Print frame function name.  */
@@ -1104,20 +902,11 @@ py_print_frame (PyObject *filter, int flags,
 	      return EXT_LANG_BT_ERROR;
 	    }
 
-	  TRY
-	    {
-	      annotate_frame_function_name ();
-	      if (function == NULL)
-		out->field_skip ("func");
-	      else
-		out->field_string ("func", function);
-	    }
-	  CATCH (except, RETURN_MASK_ERROR)
-	    {
-	      gdbpy_convert_exception (except);
-	      return EXT_LANG_BT_ERROR;
-	    }
-	  END_CATCH
+	  annotate_frame_function_name ();
+	  if (function == NULL)
+	    out->field_skip ("func");
+	  else
+	    out->field_string ("func", function);
 	}
     }
 
@@ -1133,16 +922,7 @@ py_print_frame (PyObject *filter, int flags,
   /* File name/source/line number information.  */
   if (print_frame_info)
     {
-      TRY
-	{
-	  annotate_frame_source_begin ();
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      annotate_frame_source_begin ();
 
       if (PyObject_HasAttrString (filter, "filename"))
 	{
@@ -1159,20 +939,11 @@ py_print_frame (PyObject *filter, int flags,
 	      if (filename == NULL)
 		return EXT_LANG_BT_ERROR;
 
-	      TRY
-		{
-		  out->wrap_hint ("   ");
-		  out->text (" at ");
-		  annotate_frame_source_file ();
-		  out->field_string ("file", filename.get ());
-		  annotate_frame_source_file_end ();
-		}
-	      CATCH (except, RETURN_MASK_ERROR)
-		{
-		  gdbpy_convert_exception (except);
-		  return EXT_LANG_BT_ERROR;
-		}
-	      END_CATCH
+	      out->wrap_hint ("   ");
+	      out->text (" at ");
+	      annotate_frame_source_file ();
+	      out->field_string ("file", filename.get ());
+	      annotate_frame_source_file_end ();
 	    }
 	}
 
@@ -1190,18 +961,9 @@ py_print_frame (PyObject *filter, int flags,
 	      if (PyErr_Occurred ())
 		return EXT_LANG_BT_ERROR;
 
-	      TRY
-		{
-		  out->text (":");
-		  annotate_frame_source_line ();
-		  out->field_int ("line", line);
-		}
-	      CATCH (except, RETURN_MASK_ERROR)
-		{
-		  gdbpy_convert_exception (except);
-		  return EXT_LANG_BT_ERROR;
-		}
-	      END_CATCH
+	      out->text (":");
+	      annotate_frame_source_line ();
+	      out->field_int ("line", line);
 	    }
 	}
     }
@@ -1210,17 +972,8 @@ py_print_frame (PyObject *filter, int flags,
      elided frames, so if MI output detected do not send newline.  */
   if (! out->is_mi_like_p ())
     {
-      TRY
-	{
-	  annotate_frame_end ();
-	  out->text ("\n");
-	}
-      CATCH (except, RETURN_MASK_ERROR)
-	{
-	  gdbpy_convert_exception (except);
-	  return EXT_LANG_BT_ERROR;
-	}
-      END_CATCH
+      annotate_frame_end ();
+      out->text ("\n");
     }
 
   if (print_locals)
@@ -1409,8 +1162,17 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
 	  break;
 	}
 
-      success = py_print_frame (item.get (), flags, args_type, out, 0,
-				levels_printed.get ());
+      TRY
+	{
+	  success = py_print_frame (item.get (), flags, args_type, out, 0,
+				    levels_printed.get ());
+	}
+      CATCH (except, RETURN_MASK_ERROR)
+	{
+	  gdbpy_convert_exception (except);
+	  success = EXT_LANG_BT_ERROR;
+	}
+      END_CATCH
 
       /* Do not exit on error printing a single frame.  Print the
 	 error and continue with other frames.  */
-- 
2.9.4

Re: [RFA v2 12/13] Simplify exception handling in py-framefilter.c

[Pedro Alves]

On 08/14/2017 04:40 AM, Tom Tromey wrote:
> This patch changes py-framefilter.c as suggested by Pedro in:
> https://sourceware.org/ml/gdb-patches/2017-06/msg00748.html
> 
> In particular, gdb exceptions are now caught at the outermost layer,
> rather than in each particular function.  This simplifies much of the
> code.

Nice!  LGTM.

Thanks,
Pedro Alves

[RFA v2 10/13] Call wrap_hint in one more spot in py-framefilter.c

[Tom Tromey]

PR python/16486 notes that "bt" output is still wrapped differently
when a frame filter is in use.  This patch brings it a bit closer by
adding one more wrap_hint call, in a place where stack.c does this as
well.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR python/16486:
	* python/py-framefilter.c (py_print_args): Call wrap_hint.
---
 gdb/ChangeLog               | 5 +++++
 gdb/python/py-framefilter.c | 1 +
 2 files changed, 6 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e5aeb22..9af53f8 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	PR python/16486:
+	* python/py-framefilter.c (py_print_args): Call wrap_hint.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* python/py-framefilter.c (py_print_single_arg): Return
 	EXT_LANG_BT_ERROR from catch.
 
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 73f2a31..7114030 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -864,6 +864,7 @@ py_print_args (PyObject *filter,
 
   TRY
     {
+      out->wrap_hint ("   ");
       annotate_frame_args ();
       if (! out->is_mi_like_p ())
 	out->text (" (");
-- 
2.9.4

[RFA v2 04/13] Remove EXT_LANG_BT_COMPLETED

[Tom Tromey]

While looking at the frame filter code, I noticed that
EXT_LANG_BT_COMPLETED is not really needed.  Semantically there is no
difference between the "completed" and "ok" results.  So, this patch
removes this constant.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (py_print_frame): Return
	EXT_LANG_BT_OK.
	(gdbpy_apply_frame_filter): Update comment.
	* extension.h (enum ext_lang_bt_status) <EXT_LANG_BT_COMPLETED>:
	Remove.
	<EXT_LANG_BT_NO_FILTERS>: Change value.
---
 gdb/ChangeLog               | 9 +++++++++
 gdb/extension.h             | 6 +-----
 gdb/python/py-framefilter.c | 8 ++++----
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dd6459e..08fb316 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,14 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* python/py-framefilter.c (py_print_frame): Return
+	EXT_LANG_BT_OK.
+	(gdbpy_apply_frame_filter): Update comment.
+	* extension.h (enum ext_lang_bt_status) <EXT_LANG_BT_COMPLETED>:
+	Remove.
+	<EXT_LANG_BT_NO_FILTERS>: Change value.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	PR backtrace/15582:
 	* stack.c (backtrace_command): Parse "elide" argument.
 	* python/py-framefilter.c (py_print_frame): Handle PRINT_ELIDE.
diff --git a/gdb/extension.h b/gdb/extension.h
index 7c35502..59205e1 100644
--- a/gdb/extension.h
+++ b/gdb/extension.h
@@ -76,13 +76,9 @@ enum ext_lang_bt_status
        succeeded.  */
     EXT_LANG_BT_OK = 1,
 
-    /* Return when the frame filter process is complete, and all
-       operations have succeeded.  */
-    EXT_LANG_BT_COMPLETED = 2,
-
     /* Return when the frame filter process is complete, but there
        were no filter registered and enabled to process.  */
-    EXT_LANG_BT_NO_FILTERS = 3
+    EXT_LANG_BT_NO_FILTERS = 2
   };
 
 /* Flags to pass to apply_extlang_frame_filter.  */
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index f0474a9..2bbbfbe 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -916,7 +916,7 @@ py_print_args (PyObject *filter,
     containing all the frames level that have already been printed.
     If a frame level has been printed, do not print it again (in the
     case of elided frames).  Returns EXT_LANG_BT_ERROR on error, with any
-    GDB exceptions converted to a Python exception, or EXT_LANG_BT_COMPLETED
+    GDB exceptions converted to a Python exception, or EXT_LANG_BT_OK
     on success.  It can also throw an exception RETURN_QUIT.  */
 
 static enum ext_lang_bt_status
@@ -969,7 +969,7 @@ py_print_frame (PyObject *filter, int flags,
       if (py_mi_print_variables (filter, out, &opts,
 				 args_type, frame) == EXT_LANG_BT_ERROR)
 	return EXT_LANG_BT_ERROR;
-      return EXT_LANG_BT_COMPLETED;
+      return EXT_LANG_BT_OK;
     }
 
   gdb::optional<ui_out_emit_tuple> tuple;
@@ -1270,7 +1270,7 @@ py_print_frame (PyObject *filter, int flags,
 	}
     }
 
-  return EXT_LANG_BT_COMPLETED;
+  return EXT_LANG_BT_OK;
 }
 
 /* Helper function to initiate frame filter invocation at starting
@@ -1328,7 +1328,7 @@ bootstrap_python_frame_filters (struct frame_info *frame,
     format, OUT is the output stream to print.  FRAME_LOW is the
     beginning of the slice of frames to print, and FRAME_HIGH is the
     upper limit of the frames to count.  Returns EXT_LANG_BT_ERROR on error,
-    or EXT_LANG_BT_COMPLETED on success.  */
+    or EXT_LANG_BT_OK on success.  */
 
 enum ext_lang_bt_status
 gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
-- 
2.9.4

[RFA v2 05/13] Avoid manual resource management in py-framefilter.c

[Tom Tromey]

This patch removes the last bit of manual resource management from
py-framefilter.c.  This will be useful in the next patch.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (enumerate_args): Use
	gdb::unique_xmalloc_ptr.
---
 gdb/ChangeLog               |  5 +++++
 gdb/python/py-framefilter.c | 20 +++++---------------
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 08fb316..dc4c39f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* python/py-framefilter.c (enumerate_args): Use
+	gdb::unique_xmalloc_ptr.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* python/py-framefilter.c (py_print_frame): Return
 	EXT_LANG_BT_OK.
 	(gdbpy_apply_frame_filter): Update comment.
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 2bbbfbe..2ae2158 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -560,6 +560,9 @@ enumerate_args (PyObject *iter,
 	    }
 	  END_CATCH
 
+	  gdb::unique_xmalloc_ptr<char> arg_holder (arg.error);
+	  gdb::unique_xmalloc_ptr<char> entry_holder (entryarg.error);
+
 	  /* The object has not provided a value, so this is a frame
 	     argument to be read by GDB.  In this case we have to
 	     account for entry-values.  */
@@ -571,11 +574,7 @@ enumerate_args (PyObject *iter,
 				       args_type,
 				       print_args_field,
 				       NULL) == EXT_LANG_BT_ERROR)
-		{
-		  xfree (arg.error);
-		  xfree (entryarg.error);
-		  return EXT_LANG_BT_ERROR;
-		}
+		return EXT_LANG_BT_ERROR;
 	    }
 
 	  if (entryarg.entry_kind != print_entry_values_no)
@@ -589,8 +588,6 @@ enumerate_args (PyObject *iter,
 		    }
 		  CATCH (except, RETURN_MASK_ALL)
 		    {
-		      xfree (arg.error);
-		      xfree (entryarg.error);
 		      gdbpy_convert_exception (except);
 		      return EXT_LANG_BT_ERROR;
 		    }
@@ -600,15 +597,8 @@ enumerate_args (PyObject *iter,
 	      if (py_print_single_arg (out, NULL, &entryarg, NULL, &opts,
 				       args_type, print_args_field, NULL)
 		  == EXT_LANG_BT_ERROR)
-		{
-		  xfree (arg.error);
-		  xfree (entryarg.error);
-		  return EXT_LANG_BT_ERROR;
-		}
+		return EXT_LANG_BT_ERROR;
 	    }
-
-	  xfree (arg.error);
-	  xfree (entryarg.error);
 	}
       else
 	{
-- 
2.9.4

[RFA v2 03/13] Allow elision of some filtered frames

[Tom Tromey]

When a frame filter elides some frames, they are still printed by
"bt", indented a few spaces.  PR backtrace/15582 notes that it would
be nice for users if elided frames could simply be dropped.  This
patch adds this capability.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR backtrace/15582:
	* stack.c (backtrace_command): Parse "elide" argument.
	* python/py-framefilter.c (py_print_frame): Handle PRINT_ELIDE.
	* extension.h (enum frame_filter_flags) <PRINT_ELIDE>: New
	constant.

doc/ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR backtrace/15582:
	* gdb.texinfo (Backtrace): Mention "elide" argument.

testsuite/ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR backtrace/15582:
	* gdb.python/py-framefilter.exp: Add "bt elide" test.
---
 gdb/ChangeLog                               |  8 +++++
 gdb/doc/ChangeLog                           |  5 +++
 gdb/doc/gdb.texinfo                         |  6 ++++
 gdb/extension.h                             |  3 ++
 gdb/python/py-framefilter.c                 | 50 ++++++++++++++---------------
 gdb/stack.c                                 |  2 ++
 gdb/testsuite/ChangeLog                     |  5 +++
 gdb/testsuite/gdb.python/py-framefilter.exp |  3 ++
 8 files changed, 57 insertions(+), 25 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bd18b53..dd6459e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	PR backtrace/15582:
+	* stack.c (backtrace_command): Parse "elide" argument.
+	* python/py-framefilter.c (py_print_frame): Handle PRINT_ELIDE.
+	* extension.h (enum frame_filter_flags) <PRINT_ELIDE>: New
+	constant.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* stack.c (backtrace_command_1): Remove "show_locals" parameter,
 	add "flags".
 	(backtrace_command): Remove "fulltrace", add "flags".
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 2592745..4992fe5 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,5 +1,10 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	PR backtrace/15582:
+	* gdb.texinfo (Backtrace): Mention "elide" argument.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* gdb.texinfo (Backtrace): Describe options individually.
 
 2017-08-12  Sergio Durigan Junior  <sergiodj@redhat.com>
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index bd19d4a..3f77114 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -7226,6 +7226,12 @@ Filter API}, for more information.  Additionally use @ref{disable
 frame-filter all} to turn off all frame filters.  This is only
 relevant when @value{GDBN} has been configured with @code{Python}
 support.
+
+@item backtrace elide
+A Python frame filter might decide to ``elide'' some frames.  Normally
+such elided frames are still printed, but they are indented relative
+to the filtered frames that cause them to be elided.  The @code{elide}
+option causes elided frames to not be printed at all.
 @end table
 
 @kindex where
diff --git a/gdb/extension.h b/gdb/extension.h
index 2c79411..7c35502 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 elided frames should not be printed.  */
+    PRINT_ELIDE = 32,
   };
 
 /* 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..f0474a9 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -1238,37 +1238,37 @@ py_print_frame (PyObject *filter, int flags,
 	return EXT_LANG_BT_ERROR;
     }
 
-  {
-    /* Finally recursively print elided frames, if any.  */
-    gdbpy_ref<> elided (get_py_iter_from_func (filter, "elided"));
-    if (elided == NULL)
-      return EXT_LANG_BT_ERROR;
+  if ((flags & PRINT_ELIDE) == 0)
+    {
+      /* Finally recursively print elided frames, if any.  */
+      gdbpy_ref<> elided (get_py_iter_from_func (filter, "elided"));
+      if (elided == NULL)
+	return EXT_LANG_BT_ERROR;
 
-    if (elided != Py_None)
-      {
-	PyObject *item;
+      if (elided != Py_None)
+	{
+	  PyObject *item;
 
-	ui_out_emit_list inner_list_emiter (out, "children");
+	  ui_out_emit_list inner_list_emiter (out, "children");
 
-	if (! out->is_mi_like_p ())
-	  indent++;
+	  if (! out->is_mi_like_p ())
+	    indent++;
 
-	while ((item = PyIter_Next (elided.get ())))
-	  {
-	    gdbpy_ref<> item_ref (item);
+	  while ((item = PyIter_Next (elided.get ())))
+	    {
+	      gdbpy_ref<> item_ref (item);
 
-	    enum ext_lang_bt_status success = py_print_frame (item, flags,
-							      args_type, out,
-							      indent,
-							      levels_printed);
+	      enum ext_lang_bt_status success
+		= py_print_frame (item, flags, args_type, out, indent,
+				  levels_printed);
 
-	    if (success == EXT_LANG_BT_ERROR)
-	      return EXT_LANG_BT_ERROR;
-	  }
-	if (item == NULL && PyErr_Occurred ())
-	  return EXT_LANG_BT_ERROR;
-      }
-  }
+	      if (success == EXT_LANG_BT_ERROR)
+		return EXT_LANG_BT_ERROR;
+	    }
+	  if (item == NULL && PyErr_Occurred ())
+	    return EXT_LANG_BT_ERROR;
+	}
+    }
 
   return EXT_LANG_BT_COMPLETED;
 }
diff --git a/gdb/stack.c b/gdb/stack.c
index be83f6d..30fd5ce 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1888,6 +1888,8 @@ backtrace_command (char *arg, int from_tty)
 	    filters = false;
 	  else if (subset_compare (this_arg.get (), "full"))
 	    flags |= PRINT_LOCALS;
+	  else if (subset_compare (this_arg.get (), "elide"))
+	    flags |= PRINT_ELIDE;
 	  else
 	    {
 	      /* Not a recognized argument, so stop.  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 23658b0..53006d9 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
+	PR backtrace/15582:
+	* gdb.python/py-framefilter.exp: Add "bt elide" test.
+
 2017-08-12  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* lib/gdb.exp (get_valueof): Don't capture end-of-line
diff --git a/gdb/testsuite/gdb.python/py-framefilter.exp b/gdb/testsuite/gdb.python/py-framefilter.exp
index bbec48d..80aa495 100644
--- a/gdb/testsuite/gdb.python/py-framefilter.exp
+++ b/gdb/testsuite/gdb.python/py-framefilter.exp
@@ -157,6 +157,9 @@ gdb_test "bt no-filter full" \
 gdb_test "bt 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\}.*#22.*in func1 \\(\\).*#23.*in func2 \\(f=3\\).*elided = $hex \"Elided frame\".*fb = \{nothing = $hex \"Elided Foo Bar\", f = 84, s = 38\}.*bf = $hex.*" \
     "bt full with Reverse disabled"
+gdb_test "bt full elide" \
+    ".*#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\}.*#22.*in func1 \\(\\)\[^#\]*#24.*in func3 \\(i=3\\).*" \
+    "bt full elide with Reverse disabled"
 
 # Test set print frame-arguments
 # none
-- 
2.9.4

Re: [RFA v2 03/13] Allow elision of some filtered frames

[Eli Zaretskii]

> From: Tom Tromey <tom@tromey.com>
> Cc: Tom Tromey <tom@tromey.com>
> Date: Sun, 13 Aug 2017 21:40:20 -0600
> 
> doc/ChangeLog
> 2017-08-13  Tom Tromey  <tom@tromey.com>
> 
> 	PR backtrace/15582:
> 	* gdb.texinfo (Backtrace): Mention "elide" argument.

OK for this part, but I think you want to remove "backtrace" from this
line:

> +@item backtrace elide

to be consistent with the rest of the options.

[RFA v2 02/13] Change backtrace_command_1 calling to use flags

[Tom Tromey]

The next patch will add more flags to backtrace_command_1; and rather
than add another boolean argument, this patch changes it to accept a
flags value.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	* stack.c (backtrace_command_1): Remove "show_locals" parameter,
	add "flags".
	(backtrace_command): Remove "fulltrace", add "flags".
---
 gdb/ChangeLog |  6 ++++++
 gdb/stack.c   | 15 ++++++---------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a754b7d..bd18b53 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	* stack.c (backtrace_command_1): Remove "show_locals" parameter,
+	add "flags".
+	(backtrace_command): Remove "fulltrace", add "flags".
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* stack.c (backtrace_command): Rewrite command line parsing.
 
 2017-08-11  Pedro Alves  <palves@redhat.com>
diff --git a/gdb/stack.c b/gdb/stack.c
index 30d16cb..be83f6d 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1714,7 +1714,7 @@ frame_info (char *addr_exp, int from_tty)
    frames.  */
 
 static void
-backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
+backtrace_command_1 (char *count_exp, int flags, int no_filters,
 		     int from_tty)
 {
   struct frame_info *fi;
@@ -1795,11 +1795,9 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
 
   if (! no_filters)
     {
-      int flags = PRINT_LEVEL | PRINT_FRAME_INFO | PRINT_ARGS;
       enum ext_lang_frame_args arg_type;
 
-      if (show_locals)
-	flags |= PRINT_LOCALS;
+      flags |= PRINT_LEVEL | PRINT_FRAME_INFO | PRINT_ARGS;
 
       if (!strcmp (print_frame_arguments, "scalars"))
 	arg_type = CLI_SCALAR_VALUES;
@@ -1827,7 +1825,7 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
 	     the frame->prev field gets set to NULL in that case).  */
 
 	  print_frame_info (fi, 1, LOCATION, 1, 0);
-	  if (show_locals)
+	  if ((flags & PRINT_LOCALS) != 0)
 	    {
 	      struct frame_id frame_id = get_frame_id (fi);
 
@@ -1868,7 +1866,7 @@ backtrace_command_1 (char *count_exp, int show_locals, int no_filters,
 static void
 backtrace_command (char *arg, int from_tty)
 {
-  bool fulltrace = false;
+  int flags = 0;
   bool filters = true;
 
   if (arg)
@@ -1889,7 +1887,7 @@ backtrace_command (char *arg, int from_tty)
 	  if (subset_compare (this_arg.get (), "no-filters"))
 	    filters = false;
 	  else if (subset_compare (this_arg.get (), "full"))
-	    fulltrace = true;
+	    flags |= PRINT_LOCALS;
 	  else
 	    {
 	      /* Not a recognized argument, so stop.  */
@@ -1902,8 +1900,7 @@ backtrace_command (char *arg, int from_tty)
 	arg = NULL;
     }
 
-  backtrace_command_1 (arg, fulltrace /* show_locals */,
-		       !filters /* no frame-filters */, from_tty);
+  backtrace_command_1 (arg, flags, !filters /* no frame-filters */, from_tty);
 }
 
 /* Iterate over the local variables of a block B, calling CB with
-- 
2.9.4

[RFA v2 08/13] Move some code later in backtrace_command_1

[Tom Tromey]

PR backtrace/15584 notes that some code in backtrace_command_1 is not
useful when frame filters are in use.  This patch moves this code into
the no-frame-filters "if".  This also removes the unused local
"trailing_level", which I noticed while moving the code around.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR backtrace/15584:
	* stack.c (backtrace_command_1): Move some code into no-filters
	"if".
---
 gdb/ChangeLog |   6 ++++
 gdb/stack.c   | 105 +++++++++++++++++++++++++++++-----------------------------
 2 files changed, 59 insertions(+), 52 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 33db802..630e27b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	PR backtrace/15584:
+	* stack.c (backtrace_command_1): Move some code into no-filters
+	"if".
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* python/py-framefilter.c (throw_quit_or_print_exception): New
 	function.
 	(gdbpy_apply_frame_filter): Use it.
diff --git a/gdb/stack.c b/gdb/stack.c
index 30fd5ce..94f24b2 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1720,49 +1720,17 @@ backtrace_command_1 (char *count_exp, int flags, int no_filters,
   struct frame_info *fi;
   int count;
   int i;
-  struct frame_info *trailing;
-  int trailing_level, py_start = 0, py_end = 0;
+  int py_start = 0, py_end = 0;
   enum ext_lang_bt_status result = EXT_LANG_BT_ERROR;
 
   if (!target_has_stack)
     error (_("No stack."));
 
-  /* The following code must do two things.  First, it must set the
-     variable TRAILING to the frame from which we should start
-     printing.  Second, it must set the variable count to the number
-     of frames which we should print, or -1 if all of them.  */
-  trailing = get_current_frame ();
-
-  trailing_level = 0;
   if (count_exp)
     {
       count = parse_and_eval_long (count_exp);
       if (count < 0)
-	{
-	  struct frame_info *current;
-
-	  py_start = count;
-	  count = -count;
-
-	  current = trailing;
-	  while (current && count--)
-	    {
-	      QUIT;
-	      current = get_prev_frame (current);
-	    }
-
-	  /* Will stop when CURRENT reaches the top of the stack.
-	     TRAILING will be COUNT below it.  */
-	  while (current)
-	    {
-	      QUIT;
-	      trailing = get_prev_frame (trailing);
-	      current = get_prev_frame (current);
-	      trailing_level++;
-	    }
-
-	  count = -1;
-	}
+	py_start = count;
       else
 	{
 	  py_start = 0;
@@ -1775,24 +1743,6 @@ backtrace_command_1 (char *count_exp, int flags, int no_filters,
       count = -1;
     }
 
-  if (info_verbose)
-    {
-      /* Read in symbols for all of the frames.  Need to do this in a
-         separate pass so that "Reading in symbols for xxx" messages
-         don't screw up the appearance of the backtrace.  Also if
-         people have strong opinions against reading symbols for
-         backtrace this may have to be an option.  */
-      i = count;
-      for (fi = trailing; fi != NULL && i--; fi = get_prev_frame (fi))
-	{
-	  CORE_ADDR pc;
-
-	  QUIT;
-	  pc = get_frame_address_in_block (fi);
-	  expand_symtab_containing_pc (pc, find_pc_mapped_section (pc));
-	}
-    }
-
   if (! no_filters)
     {
       enum ext_lang_frame_args arg_type;
@@ -1815,6 +1765,57 @@ backtrace_command_1 (char *count_exp, int flags, int no_filters,
      "no-filters" has been specified from the command.  */
   if (no_filters ||  result == EXT_LANG_BT_NO_FILTERS)
     {
+      struct frame_info *trailing;
+
+      /* The following code must do two things.  First, it must set the
+	 variable TRAILING to the frame from which we should start
+	 printing.  Second, it must set the variable count to the number
+	 of frames which we should print, or -1 if all of them.  */
+      trailing = get_current_frame ();
+
+      if (count_exp != NULL && count < 0)
+	{
+	  struct frame_info *current;
+
+	  count = -count;
+
+	  current = trailing;
+	  while (current && count--)
+	    {
+	      QUIT;
+	      current = get_prev_frame (current);
+	    }
+
+	  /* Will stop when CURRENT reaches the top of the stack.
+	     TRAILING will be COUNT below it.  */
+	  while (current)
+	    {
+	      QUIT;
+	      trailing = get_prev_frame (trailing);
+	      current = get_prev_frame (current);
+	    }
+
+	  count = -1;
+	}
+
+      if (info_verbose)
+	{
+	  /* Read in symbols for all of the frames.  Need to do this in a
+	     separate pass so that "Reading in symbols for xxx" messages
+	     don't screw up the appearance of the backtrace.  Also if
+	     people have strong opinions against reading symbols for
+	     backtrace this may have to be an option.  */
+	  i = count;
+	  for (fi = trailing; fi != NULL && i--; fi = get_prev_frame (fi))
+	    {
+	      CORE_ADDR pc;
+
+	      QUIT;
+	      pc = get_frame_address_in_block (fi);
+	      expand_symtab_containing_pc (pc, find_pc_mapped_section (pc));
+	    }
+	}
+
       for (i = 0, fi = trailing; fi && count--; i++, fi = get_prev_frame (fi))
 	{
 	  QUIT;
-- 
2.9.4

[RFA v2 06/13] Allow C-c to work in backtrace in more cases

[Tom Tromey]

PR cli/17716 notes that it is difficult to C-c (or "q" at a pagination
prompt) while backtracing using a frame filter.  One reason for this
is that many places in py-framefilter.c use RETURN_MASK_ALL in a
try/catch.

This patch changes these spots to use RETURN_MASK_ERROR instead.  This
is safe to do because this entire file is exception safe now.

ChangeLog
2017-08-13  Tom Tromey  <tom@tromey.com>

	PR cli/17716:
	* python/py-framefilter.c (py_print_type, py_print_value)
	(enumerate_args, py_print_args, gdbpy_apply_frame_filter): Use
	RETURN_MASK_ERROR.
---
 gdb/ChangeLog               |  7 +++++++
 gdb/python/py-framefilter.c | 22 +++++++++++-----------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dc4c39f..825c099 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2017-08-13  Tom Tromey  <tom@tromey.com>
 
+	PR cli/17716:
+	* python/py-framefilter.c (py_print_type, py_print_value)
+	(enumerate_args, py_print_args, gdbpy_apply_frame_filter): Use
+	RETURN_MASK_ERROR.
+
+2017-08-13  Tom Tromey  <tom@tromey.com>
+
 	* python/py-framefilter.c (enumerate_args): Use
 	gdb::unique_xmalloc_ptr.
 
diff --git a/gdb/python/py-framefilter.c b/gdb/python/py-framefilter.c
index 2ae2158..e0a7bd0 100644
--- a/gdb/python/py-framefilter.c
+++ b/gdb/python/py-framefilter.c
@@ -215,7 +215,7 @@ py_print_type (struct ui_out *out, struct value *val)
       type_print (value_type (val), "", &stb, -1);
       out->field_stream ("type", stb);
     }
-  CATCH (except, RETURN_MASK_ALL)
+  CATCH (except, RETURN_MASK_ERROR)
     {
       gdbpy_convert_exception (except);
       return EXT_LANG_BT_ERROR;
@@ -255,7 +255,7 @@ py_print_value (struct ui_out *out, struct value *val,
 	{
 	  type = check_typedef (value_type (val));
 	}
-      CATCH (except, RETURN_MASK_ALL)
+      CATCH (except, RETURN_MASK_ERROR)
 	{
 	  gdbpy_convert_exception (except);
 	  return EXT_LANG_BT_ERROR;
@@ -282,7 +282,7 @@ py_print_value (struct ui_out *out, struct value *val,
 	  common_val_print (val, &stb, indent, opts, language);
 	  out->field_stream ("value", stb);
 	}
-      CATCH (except, RETURN_MASK_ALL)
+      CATCH (except, RETURN_MASK_ERROR)
 	{
 	  gdbpy_convert_exception (except);
 	  return EXT_LANG_BT_ERROR;
@@ -497,7 +497,7 @@ enumerate_args (PyObject *iter,
     {
       annotate_frame_args ();
     }
-  CATCH (except, RETURN_MASK_ALL)
+  CATCH (except, RETURN_MASK_ERROR)
     {
       gdbpy_convert_exception (except);
       return EXT_LANG_BT_ERROR;
@@ -553,7 +553,7 @@ enumerate_args (PyObject *iter,
 	    {
 	      read_frame_arg (sym, frame, &arg, &entryarg);
 	    }
-	  CATCH (except, RETURN_MASK_ALL)
+	  CATCH (except, RETURN_MASK_ERROR)
 	    {
 	      gdbpy_convert_exception (except);
 	      return EXT_LANG_BT_ERROR;
@@ -586,7 +586,7 @@ enumerate_args (PyObject *iter,
 		      out->text (", ");
 		      out->wrap_hint ("    ");
 		    }
-		  CATCH (except, RETURN_MASK_ALL)
+		  CATCH (except, RETURN_MASK_ERROR)
 		    {
 		      gdbpy_convert_exception (except);
 		      return EXT_LANG_BT_ERROR;
@@ -622,7 +622,7 @@ enumerate_args (PyObject *iter,
 	    {
 	      out->text (", ");
 	    }
-	  CATCH (except, RETURN_MASK_ALL)
+	  CATCH (except, RETURN_MASK_ERROR)
 	    {
 	      gdbpy_convert_exception (except);
 	      return EXT_LANG_BT_ERROR;
@@ -636,7 +636,7 @@ enumerate_args (PyObject *iter,
 	{
 	  annotate_arg_end ();
 	}
-      CATCH (except, RETURN_MASK_ALL)
+      CATCH (except, RETURN_MASK_ERROR)
 	{
 	  gdbpy_convert_exception (except);
 	  return EXT_LANG_BT_ERROR;
@@ -867,7 +867,7 @@ py_print_args (PyObject *filter,
       if (! out->is_mi_like_p ())
 	out->text (" (");
     }
-  CATCH (except, RETURN_MASK_ALL)
+  CATCH (except, RETURN_MASK_ERROR)
     {
       gdbpy_convert_exception (except);
       return EXT_LANG_BT_ERROR;
@@ -884,7 +884,7 @@ py_print_args (PyObject *filter,
       if (! out->is_mi_like_p ())
 	out->text (")");
     }
-  CATCH (except, RETURN_MASK_ALL)
+  CATCH (except, RETURN_MASK_ERROR)
     {
       gdbpy_convert_exception (except);
       return EXT_LANG_BT_ERROR;
@@ -1336,7 +1336,7 @@ gdbpy_apply_frame_filter (const struct extension_language_defn *extlang,
     {
       gdbarch = get_frame_arch (frame);
     }
-  CATCH (except, RETURN_MASK_ALL)
+  CATCH (except, RETURN_MASK_ERROR)
     {
       /* Let gdb try to print the stack trace.  */
       return EXT_LANG_BT_NO_FILTERS;
-- 
2.9.4

Re: [RFA v2 00/13] various frame filter fixes and cleanups

[Pedro Alves]

On 08/14/2017 04:40 AM, Tom Tromey wrote:

>> So "bt elide" means "elide the elided frames", not "show me the
>> elided frames too".  It's fine with me, though I mildly wonder whether
>> users will be confused by the "double negative".
> 
> "Elide" means "drop", so really "bt elide" should mean "drop whatever
> frames are droppable". Having "bt elide" mean "show the dropped
> frames" would be confusing.  But maybe another word would be better
> here, I don't know.

Maybe "bt no-elided", to go with "bt no-filters".

Because "elided frames" are a preexisting concept, and "elide" is
actually referring to that concept.

Let me try to clarify what I meant.  Note how the patch has the
confusing (to me) "elide the elided" "double negative":

+  if ((flags & PRINT_ELIDE) == 0)
+    {
+      /* Finally recursively print elided frames, if any.  */
+      gdbpy_ref<> elided (get_py_iter_from_func (filter, "elided"));
+      if (elided == NULL)
+	return EXT_LANG_BT_ERROR;

I.e., if "bt elide" is NOT in effect, frames returned by the
"elided" function are printed:

 If PRINT_ELIDE => don't print elided frames
 If not PRINT_ELIDE => print elided frames

I think my brain wants to read PRINT_ELIDE as PRINT_ELIDED, and
then it it becomes really clearly backwards:

  If PRINT_ELIDED => don't print elided frames
  If not PRINT_ELIDED => print elided frames

The "bt elide" switch name confuses me in the same way.  Looking at the
proposed manual change:

 +@item backtrace elide
 +A Python frame filter might decide to ``elide'' some frames.  Normally
 +such elided frames are still printed, but they are indented relative
 +to the filtered frames that cause them to be elided.  The @code{elide}
 +option causes elided frames to not be printed at all.
  @end table

A filter elides a frames.  And then the elide switch elides those
elided frames from view.  So there's two levels of elision, what I
was calling "double negative".

It would seem more natural to me to have a "bt no-elided" switch
meaning "don't print frames marked as elided":

 @item backtrace no-elided
 A Python frame filter might decide to ``elide'' some frames.  Normally
 such elided frames are still printed, but they are indented relative
 to the filtered frames that cause them to be elided.  The @code{no-elided}
 option causes elided frames to not be printed at all.

Or alternatively, to make gdb not print elided frames by default and
add a "bt elided" switch to print them:

 @item backtrace elided
 A Python frame filter might decide to ``elide'' some frames.  Normally
 such elided frames are not printed.  The @code{elided} option causes
 elided frames to be printed, indented relative to the filtered frames
 that cause them to be elided.  

Maybe it's just me and/or a case of "lost in translation", and I'm
fine with that.  Please do feel free to ignore.

Thanks,
Pedro Alves

Re: [RFA v2 00/13] various frame filter fixes and cleanups

[Phil Muldoon]

On 14/08/17 14:20, Pedro Alves wrote:
> On 08/14/2017 04:40 AM, Tom Tromey wrote:
> 
>>> So "bt elide" means "elide the elided frames", not "show me the
>>> elided frames too".  It's fine with me, though I mildly wonder whether
>>> users will be confused by the "double negative".
>>
>> "Elide" means "drop", so really "bt elide" should mean "drop whatever
>> frames are droppable". Having "bt elide" mean "show the dropped
>> frames" would be confusing.  But maybe another word would be better
>> here, I don't know.
> 
> Maybe "bt no-elided", to go with "bt no-filters".
> 
> Because "elided frames" are a preexisting concept, and "elide" is
> actually referring to that concept.

I suggest hidden or show-hidden or something like that.

> 
>  @item backtrace no-elided
>  A Python frame filter might decide to ``elide'' some frames.  Normally
>  such elided frames are still printed, but they are indented relative
>  to the filtered frames that cause them to be elided.  The @code{no-elided}
>  option causes elided frames to not be printed at all.
> 
> Or alternatively, to make gdb not print elided frames by default and
> add a "bt elided" switch to print them:
> 
>  @item backtrace elided
>  A Python frame filter might decide to ``elide'' some frames.  Normally
>  such elided frames are not printed.  The @code{elided} option causes
>  elided frames to be printed, indented relative to the filtered frames
>  that cause them to be elided.  

I'd prefer a "hidden" attribute to the frame decorators (or a callback
API like the rest of the functions). Returns True or False. GDB would
honour this and print/not print the frame according to the value
returned. This is better, to me, than a global override printing/not
printing all elided frames. The bt command should still have a global
override (IE, elide, or hidden, or show-hidden, or whatever) as
discussed in the patch, and that would allow the user final and manual
control of what is printed or not. I prefer frame decorators to be
able to decide what should, or should not, be printed as the default
as it's the presentation layer.

What do you think?

Cheers

Phil

Re: [RFA v2 00/13] various frame filter fixes and cleanups

[Pedro Alves]

On 08/14/2017 02:57 PM, Phil Muldoon wrote:

> I'd prefer a "hidden" attribute to the frame decorators (or a callback
> API like the rest of the functions). Returns True or False. GDB would
> honour this and print/not print the frame according to the value
> returned. This is better, to me, than a global override printing/not
> printing all elided frames. 
> The bt command should still have a global
> override (IE, elide, or hidden, or show-hidden, or whatever) as
> discussed in the patch, and that would allow the user final and manual
> control of what is printed or not. I prefer frame decorators to be
> able to decide what should, or should not, be printed as the default
> as it's the presentation layer.
> 
> What do you think?

Hmm, I think I'm missing the point of the difference?  Can you expand on
when would a filter want to hide elided frames, and when would it want
to show  them?  When would it want to non-elided, but hidden frame?
What's semantically different between an elided frame and a hidden 
frame?  Because "hidden" and "elided" sound like synonyms to me:
<https://en.wiktionary.org/wiki/elide> - "To leave out or omit (something).".

Thanks,
Pedro Alves

Re: [RFA v2 00/13] various frame filter fixes and cleanups

[Pedro Alves]

On 08/14/2017 04:40 AM, Tom Tromey wrote:
> I believe this new series addresses all the review comments.  However,
> there have been changes and additions, so you will probably want to
> re-read everything, and especially the new final patch.

I re-read the whole series, and it all looks good to me.

Thanks,
Pedro Alves