gdb: use intrusive_list for breakpoint locations

Replace the hand-maintained linked lists of breakpoint locations with
and intrusive list.

 - Remove breakpoint::loc, add breakpoint::m_locations.

 - Add methods for the various manipulations that need to be done on the
   location list, while maintaining reasonably good encapsulation.

 - bp_location currently has a default constructor because of one use
   in hoist_existing_locations.  hoist_existing_locations now returns a
   bp_location_list, and doesn't need the default-constructor
   bp_location anymore, so remove the bp_location default constructor.

 - I needed to add a call to clear_locations in delete_breakpoint to
   avoid a use-after-free.

 - Add a breakpoint::last_loc method, for use in
   set_breakpoint_condition.

bp_location_range uses reference_to_pointer_iterator, so that all
existing callers of breakpoint::locations don't need to change right
now.  It will be removed in the next patch.

The rest of the changes are to adapt the call sites to use the new
methods, of breakpoint::locations, rather than breakpoint::loc directly.

Change-Id: I25f7ee3d66a4e914a0540589ac414b3b820b6e70
Reviewed-By: Andrew Burgess <aburgess@redhat.com>

1 files changed, 58 insertions, 21 deletions

diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index 9f49ed6..54a7a3d 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -33,6 +33,7 @@
 #include "gdbsupport/next-iterator.h"
 #include "gdbsupport/iterator-range.h"
 #include "gdbsupport/refcounted-object.h"
+#include "gdbsupport/reference-to-pointer-iterator.h"
 #include "gdbsupport/safe-iterator.h"
 #include "cli/cli-script.h"
 #include "target/waitstatus.h"
@@ -321,11 +322,9 @@ enum bp_loc_type
   bp_loc_other			/* Miscellaneous...  */
 };
 
-class bp_location : public refcounted_object
+class bp_location : public refcounted_object, public intrusive_list_node<bp_location>
 {
 public:
-  bp_location () = default;
-
   /* Construct a bp_location with the type inferred from OWNER's
      type.  */
   explicit bp_location (breakpoint *owner);
@@ -335,10 +334,6 @@ public:
 
   virtual ~bp_location () = default;
 
-  /* Chain pointer to the next breakpoint location for
-     the same parent breakpoint.  */
-  bp_location *next = NULL;
-
   /* Type of this breakpoint location.  */
   bp_loc_type loc_type {};
 
@@ -609,9 +604,11 @@ enum watchpoint_triggered
 
 extern bool target_exact_watchpoints;
 
-/* bp_location linked list range.  */
-
-using bp_location_range = next_range<bp_location>;
+using bp_location_list = intrusive_list<bp_location>;
+using bp_location_iterator = bp_location_list::iterator;
+using bp_location_pointer_iterator
+  = reference_to_pointer_iterator<bp_location_iterator>;
+using bp_location_range = iterator_range<bp_location_pointer_iterator>;
 
 /* Note that the ->silent field is not currently used by any commands
    (though the code is in there if it was to be, and set_raw_breakpoint
@@ -633,30 +630,73 @@ struct breakpoint
   /* Allocate a location for this breakpoint.  */
   virtual struct bp_location *allocate_location ();
 
+  /* Return a range of this breakpoint's locations.  */
+  bp_location_range locations () const;
+
+  /* Add LOC to the location list of this breakpoint, sorted by address
+     (using LOC.ADDRESS).
+
+     LOC must have this breakpoint as its owner.  LOC must not already be linked
+     in a location list.  */
+  void add_location (bp_location &loc);
+
+  /* Remove LOC from this breakpoint's location list.  The name is a bit funny
+     because remove_location is already taken, and means something else.
+
+     LOC must be have this breakpoints as its owner.  LOC must be linked in this
+     breakpoint's location list.  */
+  void unadd_location (bp_location &loc);
+
+  /* Clear the location list of this breakpoint.  */
+  void clear_locations ()
+  { m_locations.clear (); }
+
+  /* Split all locations of this breakpoint that are bound to PSPACE out of its
+     location list to a separate list and return that list.  If
+     PSPACE is nullptr, hoist out all locations.  */
+  bp_location_list steal_locations (program_space *pspace);
+
   /* Return true if this breakpoint has a least one location.  */
   bool has_locations () const
-  { return this->loc != nullptr; }
+  { return !m_locations.empty (); }
 
   /* Return true if this breakpoint has a single location.  */
   bool has_single_location () const
-  { return this->loc != nullptr && this->loc->next == nullptr; }
+  {
+    if (!this->has_locations ())
+      return false;
+
+    return std::next (m_locations.begin ()) == m_locations.end ();
+  }
 
   /* Return true if this breakpoint has multiple locations.  */
   bool has_multiple_locations () const
-  { return this->loc != nullptr && this->loc->next != nullptr; }
+  {
+    if (!this->has_locations ())
+      return false;
+
+    return std::next (m_locations.begin ()) != m_locations.end ();
+  }
 
   /* Return a reference to the first location of this breakpoint.  */
   bp_location &first_loc ()
   {
     gdb_assert (this->has_locations ());
-    return *this->loc;
+    return m_locations.front ();
   }
 
   /* Return a reference to the first location of this breakpoint.  */
   const bp_location &first_loc () const
   {
     gdb_assert (this->has_locations ());
-    return *this->loc;
+    return m_locations.front ();
+  }
+
+  /* Return a reference to the last location of this breakpoint.  */
+  const bp_location &last_loc () const
+  {
+    gdb_assert (this->has_locations ());
+    return m_locations.back ();
   }
 
   /* Reevaluate a breakpoint.  This is necessary after symbols change
@@ -753,9 +793,6 @@ struct breakpoint
     /* Nothing to do.  */
   }
 
-  /* Return a range of this breakpoint's locations.  */
-  bp_location_range locations () const;
-
   breakpoint *next = NULL;
   /* Type of breakpoint.  */
   bptype type = bp_none;
@@ -766,9 +803,6 @@ struct breakpoint
   /* Number assigned to distinguish breakpoints.  */
   int number = 0;
 
-  /* Location(s) associated with this high-level breakpoint.  */
-  bp_location *loc = NULL;
-
   /* True means a silent breakpoint (don't print frame info if we stop
      here).  */
   bool silent = false;
@@ -864,6 +898,9 @@ protected:
      thread 1", which needs outputting before any breakpoint-type
      specific extra command necessary for B's recreation.  */
   void print_recreate_thread (struct ui_file *fp) const;
+
+  /* Location(s) associated with this high-level breakpoint.  */
+  bp_location_list m_locations;
 };
 
 /* Abstract base class representing code breakpoints.  User "break"