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author | Pedro Alves <pedro@palves.net> | 2020-10-30 18:26:15 +0100 |
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committer | Pedro Alves <pedro@palves.net> | 2020-10-30 01:01:12 +0000 |
commit | 79952e69634bd02029e79676a38915de60052e89 (patch) | |
tree | 74f734787fcea919e5f6166aef3775147e7946a7 /gdb/stack.c | |
parent | 4dd5c35212cf4685bb14f7709508de22a36e7dc2 (diff) | |
download | fsf-binutils-gdb-79952e69634bd02029e79676a38915de60052e89.zip fsf-binutils-gdb-79952e69634bd02029e79676a38915de60052e89.tar.gz fsf-binutils-gdb-79952e69634bd02029e79676a38915de60052e89.tar.bz2 |
Make scoped_restore_current_thread's cdtors exception free (RFC)
If the remote target closes while we're reading registers/memory for
restoring the selected frame in scoped_restore_current_thread's dtor,
the corresponding TARGET_CLOSE_ERROR error is swallowed by the
scoped_restore_current_thread's dtor, because letting exceptions
escape from a dtor is bad. It isn't great to lose that errors like
that, though. I've been thinking about how to avoid it, and I came up
with this patch.
The idea here is to make scoped_restore_current_thread's dtor do as
little as possible, to avoid any work that might throw in the first
place. And to do that, instead of having the dtor call
restore_selected_frame, which re-finds the previously selected frame,
just record the frame_id/level of the desired selected frame, and have
get_selected_frame find the frame the next time it is called. In
effect, this implements most of Cagney's suggestion, here:
/* On demand, create the selected frame and then return it. If the
selected frame can not be created, this function prints then throws
an error. When MESSAGE is non-NULL, use it for the error message,
otherwize use a generic error message. */
/* FIXME: cagney/2002-11-28: At present, when there is no selected
frame, this function always returns the current (inner most) frame.
It should instead, when a thread has previously had its frame
selected (but not resumed) and the frame cache invalidated, find
and then return that thread's previously selected frame. */
extern struct frame_info *get_selected_frame (const char *message);
The only thing missing to fully implement that would be to make
reinit_frame_cache just clear selected_frame instead of calling
select_frame(NULL), and the call select_frame(NULL) explicitly in the
places where we really wanted reinit_frame_cache to go back to the
current frame too. That can done separately, though, I'm not
proposing to do that in this patch.
Note that this patch renames restore_selected_frame to
lookup_selected_frame, and adds a new restore_selected_frame function
that doesn't throw, to be paired with the also-new save_selected_frame
function.
There's a restore_selected_frame function in infrun.c that I think can
be replaced by the new one in frame.c.
Also done in this patch is make the get_selected_frame's parameter be
optional, so that we don't have to pass down nullptr explicitly all
over the place.
lookup_selected_frame should really move from thread.c to frame.c, but
I didn't do that here, just to avoid churn in the patch while it
collects comments. I did make it extern and declared it in frame.h
already, preparing for the move. I will do the move as a follow up
patch if people agree with this approach.
Incidentally, this patch alone would fix the crashes fixed by the
previous patches in the series, because with this,
scoped_restore_current_thread's constructor doesn't throw either.
gdb/ChangeLog:
* blockframe.c (block_innermost_frame): Use get_selected_frame.
* frame.c
(scoped_restore_selected_frame::scoped_restore_selected_frame):
Use save_selected_frame. Save language as well.
(scoped_restore_selected_frame::~scoped_restore_selected_frame):
Use restore_selected_frame, and restore language as well.
(selected_frame_id, selected_frame_level): New.
(selected_frame): Update comments.
(save_selected_frame, restore_selected_frame): New.
(get_selected_frame): Use lookup_selected_frame.
(get_selected_frame_if_set): Delete.
(select_frame): Record selected_frame_level and selected_frame_id.
* frame.h (scoped_restore_selected_frame) <m_level, m_lang>: New
fields.
(get_selected_frame): Make 'message' parameter optional.
(get_selected_frame_if_set): Delete declaration.
(select_frame): Update comments.
(save_selected_frame, restore_selected_frame)
(lookup_selected_frame): Declare.
* gdbthread.h (scoped_restore_current_thread) <m_lang>: New field.
* infrun.c (struct infcall_control_state) <selected_frame_level>:
New field.
(save_infcall_control_state): Use save_selected_frame.
(restore_selected_frame): Delete.
(restore_infcall_control_state): Use restore_selected_frame.
* stack.c (select_frame_command_core, frame_command_core): Use
get_selected_frame.
* thread.c (restore_selected_frame): Rename to ...
(lookup_selected_frame): ... this and make extern. Select the
current frame if the frame level is -1.
(scoped_restore_current_thread::restore): Also restore the
language.
(scoped_restore_current_thread::~scoped_restore_current_thread):
Don't try/catch.
(scoped_restore_current_thread::scoped_restore_current_thread):
Save the language as well. Use save_selected_frame.
Change-Id: I73fd1cfc40d8513c28e5596383b7ecd8bcfe700f
Diffstat (limited to 'gdb/stack.c')
-rw-r--r-- | gdb/stack.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/gdb/stack.c b/gdb/stack.c index 4ba5500..83c3366 100644 --- a/gdb/stack.c +++ b/gdb/stack.c @@ -1842,9 +1842,9 @@ trailing_outermost_frame (int count) static void select_frame_command_core (struct frame_info *fi, bool ignored) { - struct frame_info *prev_frame = get_selected_frame_if_set (); + frame_info *prev_frame = get_selected_frame (); select_frame (fi); - if (get_selected_frame_if_set () != prev_frame) + if (get_selected_frame () != prev_frame) gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME); } @@ -1863,10 +1863,9 @@ select_frame_for_mi (struct frame_info *fi) static void frame_command_core (struct frame_info *fi, bool ignored) { - struct frame_info *prev_frame = get_selected_frame_if_set (); - + frame_info *prev_frame = get_selected_frame (); select_frame (fi); - if (get_selected_frame_if_set () != prev_frame) + if (get_selected_frame () != prev_frame) gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME); else print_selected_thread_frame (current_uiout, USER_SELECTED_FRAME); |