[PATCH 09/12] gdb: link breakpoints with intrusive_list

[Simon Marchi <simon.marchi@efficios.com>]

Replace the hand-maintained linked list with an intrusive_list.
Since the breakpoint list (breakpoint_chain) is internal to
breakpoint.c, the changes are mostly localized in breakpoint.c.

Use reference_to_pointer_iterator to implement breakpoint_range, such
that users of all_breakpoints and all_tracepoints don't need to change
right now.  It is removed in the following patch.

Nothing too surprising other than that.

Change-Id: I043d8d6f3dd864d80d5088f6ffc2c098337249ea
---
 gdb/breakpoint.c | 36 ++++++++++--------------------------
 gdb/breakpoint.h | 13 ++++++++-----
 2 files changed, 18 insertions(+), 31 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index bd3258a742e2..5f47dc777438 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -614,14 +614,16 @@ bool target_exact_watchpoints = false;
 
 /* Chains of all breakpoints defined.  */
 
-static struct breakpoint *breakpoint_chain;
+static intrusive_list<breakpoint> breakpoint_chain;
 
 /* See breakpoint.h.  */
 
 breakpoint_range
 all_breakpoints ()
 {
-  return breakpoint_range (breakpoint_chain);
+  return breakpoint_range
+    (breakpoint_pointer_iterator (breakpoint_chain.begin ()),
+     breakpoint_pointer_iterator (breakpoint_chain.end ()));
 }
 
 /* See breakpoint.h.  */
@@ -637,7 +639,9 @@ all_breakpoints_safe ()
 tracepoint_range
 all_tracepoints ()
 {
-  return tracepoint_range (breakpoint_chain);
+  return tracepoint_range
+    (tracepoint_iterator (breakpoint_pointer_iterator (breakpoint_chain.begin ())),
+     tracepoint_iterator (breakpoint_pointer_iterator (breakpoint_chain.end ())));
 }
 
 /* Array is sorted by bp_location_is_less_than - primarily by the ADDRESS.  */
@@ -7432,23 +7436,12 @@ decref_bp_location (struct bp_location **blp)
 static breakpoint *
 add_to_breakpoint_chain (std::unique_ptr<breakpoint> &&b)
 {
-  struct breakpoint *b1;
-  struct breakpoint *result = b.get ();
-
   /* Add this breakpoint to the end of the chain so that a list of
      breakpoints will come out in order of increasing numbers.  */
 
-  b1 = breakpoint_chain;
-  if (b1 == 0)
-    breakpoint_chain = b.release ();
-  else
-    {
-      while (b1->next)
-	b1 = b1->next;
-      b1->next = b.release ();
-    }
+  breakpoint_chain.push_back (*b.release ());
 
-  return result;
+  return &breakpoint_chain.back ();
 }
 
 /* Initialize loc->function_name.  */
@@ -12385,15 +12378,7 @@ delete_breakpoint (struct breakpoint *bpt)
   if (bpt->number)
     gdb::observers::breakpoint_deleted.notify (bpt);
 
-  if (breakpoint_chain == bpt)
-    breakpoint_chain = bpt->next;
-
-  for (breakpoint *b : all_breakpoints ())
-    if (b->next == bpt)
-      {
-	b->next = bpt->next;
-	break;
-      }
+  breakpoint_chain.erase (breakpoint_chain.iterator_to (*bpt));
 
   /* Be sure no bpstat's are pointing at the breakpoint after it's
      been freed.  */
@@ -14456,7 +14441,6 @@ _initialize_breakpoint ()
   gdb::observers::memory_changed.attach (invalidate_bp_value_on_memory_change,
 					 "breakpoint");
 
-  breakpoint_chain = 0;
   /* Don't bother to call set_breakpoint_count.  $bpnum isn't useful
      before a breakpoint is set.  */
   breakpoint_count = 0;
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index 8c9541902cdd..a03b57734b9d 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -616,7 +616,7 @@ using bp_location_range = iterator_range<bp_location_iterator>;
 
 /* Abstract base class representing all kinds of breakpoints.  */
 
-struct breakpoint
+struct breakpoint : public intrusive_list_node<breakpoint>
 {
   breakpoint (struct gdbarch *gdbarch_, enum bptype bptype,
 	      bool temp = true, const char *cond_string = nullptr);
@@ -789,7 +789,6 @@ struct breakpoint
     /* Nothing to do.  */
   }
 
-  breakpoint *next = NULL;
   /* Type of breakpoint.  */
   bptype type = bp_none;
   /* Zero means disabled; remember the info but don't break here.  */
@@ -1892,11 +1891,15 @@ class scoped_rbreak_breakpoints
 
 /* Breakpoint linked list iterator.  */
 
-using breakpoint_iterator = next_iterator<breakpoint>;
+using breakpoint_list = intrusive_list<breakpoint>;
+
+using breakpoint_iterator = breakpoint_list::iterator;
+
+using breakpoint_pointer_iterator = reference_to_pointer_iterator<breakpoint_iterator>;
 
 /* Breakpoint linked list range.  */
 
-using breakpoint_range = iterator_range<breakpoint_iterator>;
+using breakpoint_range = iterator_range<breakpoint_pointer_iterator>;
 
 /* Return a range to iterate over all breakpoints.  */
 
@@ -1923,7 +1926,7 @@ struct tracepoint_filter
 /* Breakpoint linked list iterator, filtering to only keep tracepoints.  */
 
 using tracepoint_iterator
-  = filtered_iterator<breakpoint_iterator, tracepoint_filter>;
+  = filtered_iterator<breakpoint_pointer_iterator, tracepoint_filter>;
 
 /* Breakpoint linked list range, filtering to only keep tracepoints.  */
 
-- 
2.40.1