* dummy-frame.h (dummy_frame_pop): Add prototype.

[deliverable/binutils-gdb.git] / gdb / frame.c

diff --git a/gdb/frame.c b/gdb/frame.c
index c4f85fe9c8a6675f62294c08b177a0a80c56af0b..55ded7168250fb311114a0b32e9f312dddbdbc65 100644 (file)
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -368,7 +368,33 @@ frame_id_eq (struct frame_id l, struct frame_id r)
   return eq;
 }
 
-int
+/* Safety net to check whether frame ID L should be inner to
+   frame ID R, according to their stack addresses.
+
+   This method cannot be used to compare arbitrary frames, as the
+   ranges of valid stack addresses may be discontiguous (e.g. due
+   to sigaltstack).
+
+   However, it can be used as safety net to discover invalid frame
+   IDs in certain circumstances.
+
+   * If frame NEXT is the immediate inner frame to THIS, and NEXT
+     is a NORMAL frame, then the stack address of NEXT must be
+     inner-than-or-equal to the stack address of THIS.
+
+     Therefore, if frame_id_inner (THIS, NEXT) holds, some unwind
+     error has occurred.
+
+   * If frame NEXT is the immediate inner frame to THIS, and NEXT
+     is a NORMAL frame, and NEXT and THIS have different stack
+     addresses, no other frame in the frame chain may have a stack
+     address in between.
+
+     Therefore, if frame_id_inner (TEST, THIS) holds, but
+     frame_id_inner (TEST, NEXT) does not hold, TEST cannot refer
+     to a valid frame in the frame chain.   */
+
+static int
 frame_id_inner (struct gdbarch *gdbarch, struct frame_id l, struct frame_id r)
 {
   int inner;
@@ -395,28 +421,34 @@ frame_id_inner (struct gdbarch *gdbarch, struct frame_id l, struct frame_id r)
 struct frame_info *
 frame_find_by_id (struct frame_id id)
 {
-  struct frame_info *frame;
+  struct frame_info *frame, *prev_frame;
 
   /* ZERO denotes the null frame, let the caller decide what to do
      about it.  Should it instead return get_current_frame()?  */
   if (!frame_id_p (id))
     return NULL;
 
-  for (frame = get_current_frame ();
-       frame != NULL;
-       frame = get_prev_frame (frame))
+  for (frame = get_current_frame (); ; frame = prev_frame)
     {
       struct frame_id this = get_frame_id (frame);
       if (frame_id_eq (id, this))
        /* An exact match.  */
        return frame;
-      if (frame_id_inner (get_frame_arch (frame), id, this))
-       /* Gone to far.  */
+
+      prev_frame = get_prev_frame (frame);
+      if (!prev_frame)
+       return NULL;
+
+      /* As a safety net to avoid unnecessary backtracing while trying
+        to find an invalid ID, we check for a common situation where
+        we can detect from comparing stack addresses that no other
+        frame in the current frame chain can have this ID.  See the
+        comment at frame_id_inner for details.   */
+      if (get_frame_type (frame) == NORMAL_FRAME
+         && !frame_id_inner (get_frame_arch (frame), id, this)
+         && frame_id_inner (get_frame_arch (prev_frame), id,
+                            get_frame_id (prev_frame)))
        return NULL;
-      /* Either we're not yet gone far enough out along the frame
-         chain (inner(this,id)), or we're comparing frameless functions
-         (same .base, different .func, no test available).  Struggle
-         on until we've definitly gone to far.  */
     }
   return NULL;
 }
@@ -517,6 +549,11 @@ frame_pop (struct frame_info *this_frame)
   scratch = frame_save_as_regcache (prev_frame);
   cleanups = make_cleanup_regcache_xfree (scratch);
 
+  /* If we are popping a dummy frame, clean up the associated
+     data as well.  */
+  if (get_frame_type (this_frame) == DUMMY_FRAME)
+    dummy_frame_pop (get_frame_id (this_frame));
+
   /* FIXME: cagney/2003-03-16: It should be possible to tell the
      target's register cache that it is about to be hit with a burst
      register transfer and that the sequence of register writes should
@@ -1207,11 +1244,10 @@ get_prev_frame_1 (struct frame_info *this_frame)
 
   /* Check that this frame's ID isn't inner to (younger, below, next)
      the next frame.  This happens when a frame unwind goes backwards.
-     Exclude signal trampolines (due to sigaltstack the frame ID can
-     go backwards) and sentinel frames (the test is meaningless).  */
-  if (this_frame->next->level >= 0
-      && this_frame->next->unwind->type != SIGTRAMP_FRAME
-      && frame_id_inner (get_frame_arch (this_frame), this_id,
+     This check is valid only if the next frame is NORMAL.  See the
+     comment at frame_id_inner for details.  */
+  if (this_frame->next->unwind->type == NORMAL_FRAME
+      && frame_id_inner (get_frame_arch (this_frame->next), this_id,
                         get_frame_id (this_frame->next)))
     {
       if (frame_debug)