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gdb: introduce explicit outer frame id kind

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In the following patch, we'll need to easily differentiate the frame_id
of the outer frame (or the frame id of a frame inlined into the outer
frame) from a simply invalid frame id.

Currently, the frame id of the outer frame has `stack_status` set to
FID_STACK_INVALID plus special_addr_p set.  A frame inlined into the
outer frame would also have `artificial_depth` set to greater than one.
That makes the job of differntiating the frame id of the outer frame (or a
frame inlined into the outer frame) cumbersome.

To make it easier, give the outer frame id its own frame_id_stack_status
enum value.  outer_frame_id then becomes very similar to
sentinel_frame_id, another "special" frame id value.

In frame_id_p, we don't need a special case for the outer frame id, as
it's no long a special case of FID_STACK_INVALID.  Same goes for
frame_id_eq.

So in the end, FID_STACK_OUTER isn't even used (except in
fprint_frame_id).  But that's expected: all the times we wanted to
identify an outer frame was to differentiate it from an otherwise
invalid frame.  Since their frame_id_stack_status value is different
now, that is done naturally.

gdb/ChangeLog:

	* frame.h (enum frame_id_stack_status) <FID_STACK_OUTER>: New.
	* frame.c (fprint_frame_id): Handle FID_STACK_OUTER.
	(outer_frame_id): Use FID_STACK_OUTER instead of
	FID_STACK_INVALID.
	(frame_id_p): Don't check for outer_frame_id.

Change-Id: I654e7f936349debc4f04f7f684b15e71a0c37619
This commit is contained in:
Simon Marchi 2020-08-31 13:23:12 -04:00
parent 8efaf6b352
commit 84154d166a
3 changed files with 20 additions and 16 deletions
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8
gdb/ChangeLog
View file

@ -1,3 +1,11 @@
2020-08-31 Simon Marchi <simon.marchi@efficios.com>
* frame.h (enum frame_id_stack_status) <FID_STACK_OUTER>: New.
* frame.c (fprint_frame_id): Handle FID_STACK_OUTER.
(outer_frame_id): Use FID_STACK_OUTER instead of
FID_STACK_INVALID.
(frame_id_p): Don't check for outer_frame_id.
2020-08-31 Simon Marchi <simon.marchi@efficios.com>
* frame-unwind.c (frame_unwind_got_optimized): Don't set

19
gdb/frame.c
View file

@ -396,8 +396,11 @@ fprint_frame_id (struct ui_file *file, struct frame_id id)
fprintf_unfiltered (file, "stack=<unavailable>");
else if (id.stack_status == FID_STACK_SENTINEL)
fprintf_unfiltered (file, "stack=<sentinel>");
else if (id.stack_status == FID_STACK_OUTER)
fprintf_unfiltered (file, "stack=<outer>");
else
fprintf_unfiltered (file, "stack=%s", hex_string (id.stack_addr));
fprintf_unfiltered (file, ",");
fprint_field (file, "code", id.code_addr_p, id.code_addr);
@ -672,7 +675,7 @@ frame_unwind_caller_id (struct frame_info *next_frame)
const struct frame_id null_frame_id = { 0 }; /* All zeros. */
const struct frame_id sentinel_frame_id = { 0, 0, 0, FID_STACK_SENTINEL, 0, 1, 0 };
const struct frame_id outer_frame_id = { 0, 0, 0, FID_STACK_INVALID, 0, 1, 0 };
const struct frame_id outer_frame_id = { 0, 0, 0, FID_STACK_OUTER, 0, 1, 0 };
struct frame_id
frame_id_build_special (CORE_ADDR stack_addr, CORE_ADDR code_addr,
@ -746,10 +749,6 @@ frame_id_p (frame_id l)
/* The frame is valid iff it has a valid stack address. */
bool p = l.stack_status != FID_STACK_INVALID;
/* outer_frame_id is also valid. */
if (!p && memcmp (&l, &outer_frame_id, sizeof (l)) == 0)
p = true;
if (frame_debug)
{
fprintf_unfiltered (gdb_stdlog, "{ frame_id_p (l=");
@ -774,15 +773,7 @@ frame_id_eq (frame_id l, frame_id r)
{
bool eq;
if (l.stack_status == FID_STACK_INVALID && l.special_addr_p
&& r.stack_status == FID_STACK_INVALID && r.special_addr_p)
/* The outermost frame marker is equal to itself. This is the
dodgy thing about outer_frame_id, since between execution steps
we might step into another function - from which we can't
unwind either. More thought required to get rid of
outer_frame_id. */
eq = true;
else if (l.stack_status == FID_STACK_INVALID
if (l.stack_status == FID_STACK_INVALID
|| r.stack_status == FID_STACK_INVALID)
/* Like a NaN, if either ID is invalid, the result is false.
Note that a frame ID is invalid iff it is the null frame ID. */

9
gdb/frame.h
View file

@ -85,8 +85,7 @@ struct frame_print_options;
enum frame_id_stack_status
{
/* Stack address is invalid. E.g., this frame is the outermost
(i.e., _start), and the stack hasn't been setup yet. */
/* Stack address is invalid. */
FID_STACK_INVALID = 0,
/* Stack address is valid, and is found in the stack_addr field. */
@ -95,6 +94,12 @@ enum frame_id_stack_status
/* Sentinel frame. */
FID_STACK_SENTINEL = 2,
/* Outer frame. Since a frame's stack address is typically defined as the
value the stack pointer had prior to the activation of the frame, an outer
frame doesn't have a stack address. The frame ids of frames inlined in the
outer frame are also of this type. */
FID_STACK_OUTER = 3,
/* Stack address is unavailable. I.e., there's a valid stack, but
we don't know where it is (because memory or registers we'd
compute it from were not collected). */