[patch v8 05/24] frame: artificial frame id's

[Markus Metzger <markus.t.metzger@intel.com>]

At the moment, a frame must have a stack - except for the outer frame.

When we analyze the recorded execution for "record btrace" to detect
function calls and compute a back trace at some point in the recorded
execution history, we will end up with frames without a stack.

To prepare for this, support frame_id's without a stack component.

CC:  Pedro Alves  <palves@redhat.com>

2013-12-12  Markus Metzger  <markus.t.metzger@intel.com>

	* frame.h (frame_id_build_artificial): New.
	* frame.c (frame_id_build_artificial): New.
	(frame_id_p): An artificial frame is valid.
	(frame_id_eq): A frame is equal to itself.


---
 gdb/frame.c | 30 +++++++++++++++++++++++-------
 gdb/frame.h |  6 ++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/gdb/frame.c b/gdb/frame.c
index ddd5e70..37d780e 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -526,6 +526,21 @@ frame_id_build_wild (CORE_ADDR stack_addr)
   return id;
 }
 
+/* See frame.h.  */
+
+struct frame_id
+frame_id_build_artificial (CORE_ADDR code_addr,
+			   CORE_ADDR special_addr)
+{
+  struct frame_id id = null_frame_id;
+
+  id.code_addr = code_addr;
+  id.code_addr_p = 1;
+  id.special_addr = special_addr;
+  id.special_addr_p = 1;
+  return id;
+}
+
 int
 frame_id_p (struct frame_id l)
 {
@@ -536,6 +551,9 @@ frame_id_p (struct frame_id l)
   /* outer_frame_id is also valid.  */
   if (!p && memcmp (&l, &outer_frame_id, sizeof (l)) == 0)
     p = 1;
+  /* An artificial frame is also valid.  */
+  if (!p && l.code_addr_p && l.special_addr_p)
+    p = 1;
   if (frame_debug)
     {
       fprintf_unfiltered (gdb_stdlog, "{ frame_id_p (l=");
@@ -559,13 +577,11 @@ frame_id_eq (struct frame_id l, struct frame_id r)
 {
   int eq;
 
-  if (!l.stack_addr_p && l.special_addr_p
-      && !r.stack_addr_p && 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.  */
+  if (memcmp (&l, &r, sizeof (l)) == 0)
+    /* Every frame 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 = 1;
   else if (!l.stack_addr_p || !r.stack_addr_p)
     /* Like a NaN, if either ID is invalid, the result is false.
diff --git a/gdb/frame.h b/gdb/frame.h
index e4e6b25..71f07dd 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -174,6 +174,12 @@ extern struct frame_id frame_id_build_special (CORE_ADDR stack_addr,
    as the special identifier address are set to indicate wild cards.  */
 extern struct frame_id frame_id_build_wild (CORE_ADDR stack_addr);
 
+/* Construct an artificial frame ID.  The first parameter is the frame's
+   constant code address (typically the function entry point), and the
+   second the frame's special identifier address.  */
+extern struct frame_id frame_id_build_artificial (CORE_ADDR code_addr,
+						  CORE_ADDR special_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.  */
-- 
1.8.3.1