[PATCH] [gdb] Support frames inlined into the outer frame

[Scott Linder <scott@scottlinder.com>]

Broaden the definition of `outer_frame_id` to effectively create a new
class of "invalid" IDs to represent frames inlined into the outer frame.
These new IDs behave like the outer frame, in that they are "invalid",
yet return true from `frame_id_p` and compare equal to themselves.

2020-03-18  Scott Linder  <scott@scottlinder.com>

	* frame.c (frame_id_p): Consider functions inlined into outer frame
	as valid.
	(frame_id_eq): Consider functions inlined into outer frame with same
	artificial_depth as equal.

	* frame.h (outer_frame_id): Update comment.
	(frame_id_p): Update comment.

	* inline-frame.c (inline_frame_this_id): Remove assert that prevents
	inline frame ids in outer frame.

Change-Id: I8aa129c667dccc31590ffdf426586418493a6ebe
---
 gdb/frame.c        | 11 ++++++-----
 gdb/frame.h        |  7 ++++---
 gdb/inline-frame.c |  4 ----
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/gdb/frame.c b/gdb/frame.c
index d74d1d5c7c..b62d68f12a 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -694,8 +694,8 @@ frame_id_p (struct frame_id l)
 
   /* The frame is valid iff it has a valid stack address.  */
   p = l.stack_status != FID_STACK_INVALID;
-  /* outer_frame_id is also valid.  */
-  if (!p && memcmp (&l, &outer_frame_id, sizeof (l)) == 0)
+  /* outer_frame_id and functions inlined into it are also valid.  */
+  if (!p && l.special_addr_p)
     p = 1;
   if (frame_debug)
     {
@@ -722,12 +722,13 @@ frame_id_eq (struct frame_id l, struct frame_id r)
 
   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
+    /* The outermost frame marker, and any inline frame markers
+       derived from it, are equal to themselves.  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 = 1;
+    eq = l.artificial_depth == r.artificial_depth;
   else 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.
diff --git a/gdb/frame.h b/gdb/frame.h
index cfc15022ed..d394382903 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -195,7 +195,8 @@ extern const struct frame_id sentinel_frame_id;
 
 /* This means "there is no frame ID, but there is a frame".  It should be
    replaced by best-effort frame IDs for the outermost frame, somehow.
-   The implementation is only special_addr_p set.  */
+   The implementation is only special_addr_p, and possibly
+   artificial_depth, set.  */
 extern const struct frame_id outer_frame_id;
 
 /* Flag to control debugging.  */
@@ -237,8 +238,8 @@ extern struct frame_id
 extern struct frame_id frame_id_build_wild (CORE_ADDR stack_addr);
 
 /* Returns non-zero when L is a valid frame (a valid frame has a
-   non-zero .base).  The outermost frame is valid even without an
-   ID.  */
+   non-zero .base).  The outermost frame and any frames inlined into it
+   are valid even without an ID.  */
 extern int frame_id_p (struct frame_id l);
 
 /* Returns non-zero when L is a valid frame representing a frame made up by GDB
diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index c650195e57..a187630840 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -171,10 +171,6 @@ inline_frame_this_id (struct frame_info *this_frame,
      frame").  This will take work.  */
   gdb_assert (frame_id_p (*this_id));
 
-  /* For now, require we don't match outer_frame_id either (see
-     comment above).  */
-  gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
-
   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
      which generates DW_AT_entry_pc for inlined functions when
      possible.  If this attribute is available, we should use it
-- 
2.17.1