Change how debugger handles source breakpoints

runtime/vm/debugger.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/debugger.h"
 
 #include "include/dart_api.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
@@ skipping 32 matching lines @@
   }
 
  private:
   GrowableObjectArray* objs_;
 
   DISALLOW_COPY_AND_ASSIGN(RemoteObjectCache);
 };
 
 
 SourceBreakpoint::SourceBreakpoint(intptr_t id,
-                                   const Function& func,
+                                   const Script& script,
                                    intptr_t token_pos)
     : id_(id),
-      function_(func.raw()),
+      script_(script.raw()),
       token_pos_(token_pos),
-      line_number_(-1),
+      is_resolved_(false),
       is_enabled_(false),
-      next_(NULL) {
-  ASSERT(!func.IsNull());
-  ASSERT((func.token_pos() <= token_pos_) &&
-         (token_pos_ <= func.end_token_pos()));
+      next_(NULL),
+      function_(Function::null()),
+      line_number_(-1) {
+  ASSERT(id_ > 0);
+  ASSERT(!script.IsNull());
+  ASSERT(token_pos_ >= 0);
 }
 
 
 void SourceBreakpoint::Enable() {
   is_enabled_ = true;
   Isolate::Current()->debugger()->SyncBreakpoint(this);
 }
 
 
 void SourceBreakpoint::Disable() {
   is_enabled_ = false;
   Isolate::Current()->debugger()->SyncBreakpoint(this);
 }
 
 
-RawScript* SourceBreakpoint::SourceCode() {
-  const Function& func = Function::Handle(function_);
-  return func.script();
+void SourceBreakpoint::SetResolved(const Function& func, intptr_t token_pos) {
+  ASSERT(func.script() == script_);
+  ASSERT((func.token_pos() <= token_pos) &&
+         (token_pos <= func.end_token_pos()));
+  function_ = func.raw();
+  token_pos_ = token_pos;
+  line_number_ = -1;  // Recalcualte lazily.
+  is_resolved_ = true;
 }
 
 
+// TODO(hausner): Get rid of library parameter. A source breakpoint location
+// does not imply a library, since the same source code can be included
+// in more than one library, e.g. the text location of mixin functions.
 void SourceBreakpoint::GetCodeLocation(
     Library* lib,
     Script* script,
-    intptr_t* pos) const {
-  const Function& func = Function::Handle(function_);
-  const Class& cls = Class::Handle(func.origin());
-  *lib = cls.library();
-  *script = func.script();
-  *pos = token_pos();
+    intptr_t* pos) {
+  *script = this->script();
+  *pos = token_pos_;
+  if (IsResolved()) {
+    const Function& func = Function::Handle(function_);
+    ASSERT(!func.IsNull());
+    const Class& cls = Class::Handle(func.origin());
+    *lib = cls.library();
+  } else {
+    *lib = Library::null();
+  }
 }
 
 
 RawString* SourceBreakpoint::SourceUrl() {
-  const Script& script = Script::Handle(SourceCode());
-  return script.url();
+  return Script::Handle(script()).url();
 }
 
 
 intptr_t SourceBreakpoint::LineNumber() {
   // Compute line number lazily since it causes scanning of the script.
   if (line_number_ < 0) {
-    const Script& script = Script::Handle(SourceCode());
+    const Script& script = Script::Handle(this->script());
     script.GetTokenLocation(token_pos_, &line_number_, NULL);
   }
   return line_number_;
 }
 
 
-void SourceBreakpoint::set_function(const Function& func) {
-  function_ = func.raw();
-}
-
-
 void SourceBreakpoint::VisitObjectPointers(ObjectPointerVisitor* visitor) {
+  visitor->VisitPointer(reinterpret_cast<RawObject**>(&script_));
   visitor->VisitPointer(reinterpret_cast<RawObject**>(&function_));
 }
 
 
-void SourceBreakpoint::PrintToJSONStream(JSONStream* stream) const {
+void SourceBreakpoint::PrintToJSONStream(JSONStream* stream) {
   Isolate* isolate = Isolate::Current();
 
   JSONObject jsobj(stream);
   jsobj.AddProperty("type", "Breakpoint");
 
   jsobj.AddProperty("id", id());
   jsobj.AddProperty("enabled", IsEnabled());
-
-  const Function& func = Function::Handle(function());
-  jsobj.AddProperty("resolved", func.HasCode());
+  jsobj.AddProperty("resolved", IsResolved());
 
   Library& library = Library::Handle(isolate);
   Script& script = Script::Handle(isolate);
   intptr_t token_pos;
   GetCodeLocation(&library, &script, &token_pos);
   {
     JSONObject location(&jsobj, "location");
     location.AddProperty("type", "Location");
-    location.AddProperty("libId", library.index());
 
     const String& url = String::Handle(script.url());
     location.AddProperty("script", url.ToCString());
     location.AddProperty("tokenPos", token_pos);
   }
 }
 
 
 void CodeBreakpoint::VisitObjectPointers(ObjectPointerVisitor* visitor) {
   visitor->VisitPointer(reinterpret_cast<RawObject**>(&function_));
@@ skipping 61 matching lines @@
   len++;  // String terminator.
   char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, kFormat,
               func_class.IsTopLevel() ? "" : class_name.ToCString(),
               func_class.IsTopLevel() ? "" : ".",
               func_name.ToCString());
   return chars;
 }
 
 
+// Returns true if function contains the token position in the given script.
+static bool FunctionContains(const Function& func,
+                             const Script& script,
+                             intptr_t token_pos) {
+  if ((func.token_pos() <= token_pos) && (token_pos <= func.end_token_pos())) {
+    // Check script equality second because it allocates
+    // handles as a side effect.
+    return func.script() == script.raw();
+  }
+  return false;
+}
+
+
 bool Debugger::HasBreakpoint(const Function& func) {
   if (!func.HasCode()) {
     // If the function is not compiled yet, just check whether there
-    // is a user-defined latent breakpoint.
+    // is a user-defined breakpoint that falls into the token
+    // range of the function. This may be a false positive: the breakpoint
+    // might be inside a local closure.
+    Script& script = Script::Handle(isolate_);
     SourceBreakpoint* sbpt = src_breakpoints_;
     while (sbpt != NULL) {
-      if (func.raw() == sbpt->function()) {
+      script = sbpt->script();
+      if (FunctionContains(func, script, sbpt->token_pos())) {
         return true;
       }
       sbpt = sbpt->next_;
     }
     return false;
   }
   CodeBreakpoint* cbpt = code_breakpoints_;
   while (cbpt != NULL) {
     if (func.raw() == cbpt->function()) {
       return true;
@@ skipping 1037 matching lines @@
   }
   DebuggerEvent event(kExceptionThrown);
   event.exception = &exc;
   ASSERT(stack_trace_ == NULL);
   stack_trace_ = stack_trace;
   Pause(&event);
   stack_trace_ = NULL;
 }
 
 
-// Given a function and a token position range, return the best fit
-// token position to set a breakpoint.
-// If multiple possible breakpoint positions are within the given range,
-// the one with the lowest machine code address is picked.
-// If no possible breakpoint location exists in the given range, the closest
-// token position after the range is returned.
+// Given a function and a token position, return the best fit
+// token position to set a breakpoint. The best fit is the safe point
+// with the lowest compiled code address that follows the requsted
+// token position.
 intptr_t Debugger::ResolveBreakpointPos(const Function& func,
-                                        intptr_t first_token_pos,
-                                        intptr_t last_token_pos) {
+                                        intptr_t requested_token_pos) {
   ASSERT(func.HasCode());
   ASSERT(!func.HasOptimizedCode());
   Code& code = Code::Handle(func.unoptimized_code());
   ASSERT(!code.IsNull());
   PcDescriptors& desc = PcDescriptors::Handle(code.pc_descriptors());
   intptr_t best_fit_index = -1;
-  intptr_t best_fit = INT_MAX;
+  intptr_t best_fit_pos = INT_MAX;
   uword lowest_pc = kUwordMax;
   intptr_t lowest_pc_index = -1;
   for (intptr_t i = 0; i < desc.Length(); i++) {
     intptr_t desc_token_pos = desc.TokenPos(i);
     ASSERT(desc_token_pos >= 0);
-    if (desc_token_pos < first_token_pos) {
-      // This descriptor is before the given range.
+    if (desc_token_pos < requested_token_pos) {
+      // This descriptor is before the first acceptable token position.
       continue;
     }
     if (IsSafePoint(desc.DescriptorKind(i))) {
-      if ((desc_token_pos - first_token_pos) < best_fit) {
-        // So far, this descriptor has the closest token position to the
-        // beginning of the range.
-        best_fit = desc_token_pos - first_token_pos;
-        ASSERT(best_fit >= 0);
+      if (desc_token_pos < best_fit_pos) {
+        // So far, this descriptor has the lowest token position after
+        // the first acceptable token position.
+        best_fit_pos = desc_token_pos;
         best_fit_index = i;
       }
-      if ((first_token_pos <= desc_token_pos) &&
-          (desc_token_pos <= last_token_pos) &&
-          (desc.PC(i) < lowest_pc)) {
-        // This descriptor is within the token position range and so
-        // far has the lowest code address.
+      if (desc.PC(i) < lowest_pc) {
+        // This descriptor so far has the lowest code address.
         lowest_pc = desc.PC(i);
         lowest_pc_index = i;
       }
     }
   }
   if (lowest_pc_index >= 0) {
-    // We found the the pc descriptor within the given token range that
-    // has the lowest execution address. This is the first possible
-    // breakpoint on the line. We use this instead of the nearest
-    // PC descriptor measured in token index distance.
+    // We found the pc descriptor that has the lowest execution address.
+    // This is the first possible breakpoint after the requested token
+    // position. We use this instead of the nearest PC descriptor
+    // measured in token index distance.
     best_fit_index = lowest_pc_index;
   }
   if (best_fit_index >= 0) {
     return desc.TokenPos(best_fit_index);
   }
   return -1;
 }
 
 
 void Debugger::MakeCodeBreakpointsAt(const Function& func,
-                                     intptr_t token_pos,
                                      SourceBreakpoint* bpt) {
+  ASSERT((bpt != NULL) && bpt->IsResolved());
   ASSERT(!func.HasOptimizedCode());
   Code& code = Code::Handle(func.unoptimized_code());
   ASSERT(!code.IsNull());
   PcDescriptors& desc = PcDescriptors::Handle(code.pc_descriptors());
   for (intptr_t i = 0; i < desc.Length(); i++) {
     intptr_t desc_token_pos = desc.TokenPos(i);
-    if ((desc_token_pos == token_pos) && IsSafePoint(desc.DescriptorKind(i))) {
+    if ((desc_token_pos == bpt->token_pos_) &&
+        IsSafePoint(desc.DescriptorKind(i))) {
       CodeBreakpoint* code_bpt = GetCodeBreakpoint(desc.PC(i));
       if (code_bpt == NULL) {
         // No code breakpoint for this code exists; create one.
         code_bpt = new CodeBreakpoint(func, i);
         RegisterCodeBreakpoint(code_bpt);
       }
       code_bpt->set_src_bpt(bpt);
-    }
-  }
-}
-
-
-SourceBreakpoint* Debugger::SetBreakpoint(const Function& target_function,
-                                          intptr_t first_token_pos,
-                                          intptr_t last_token_pos) {
-  if ((last_token_pos < target_function.token_pos()) ||
-      (target_function.end_token_pos() < first_token_pos)) {
-    // The given token position is not within the target function.
+      if (bpt->IsEnabled()) {
+        code_bpt->Enable();
+      }
+    }
+  }
+}
+
+
+void Debugger::FindEquivalentFunctions(const Script& script,
+                                       intptr_t start_pos,
+                                       intptr_t end_pos,
+                                       GrowableObjectArray* function_list) {
+  Class& cls = Class::Handle(isolate_);
+  Array& functions = Array::Handle(isolate_);
+  GrowableObjectArray& closures = GrowableObjectArray::Handle(isolate_);
+  Function& function = Function::Handle(isolate_);
+
+  const ClassTable& class_table = *isolate_->class_table();
+  const intptr_t num_classes = class_table.NumCids();
+  for (intptr_t i = 1; i < num_classes; i++) {
+    if (class_table.HasValidClassAt(i)) {
+      cls = class_table.At(i);
+      // Note: we need to check the functions of this class even if
+      // the class is defined in a differenct 'script'. There could
+      // be mixin functions from the given script in this class.
+      functions = cls.functions();
+      if (!functions.IsNull()) {
+        const intptr_t num_functions = functions.Length();
+        for (intptr_t pos = 0; pos < num_functions; pos++) {
+          function ^= functions.At(pos);
+          ASSERT(!function.IsNull());
+          // Check token position first to avoid unnecessary calls
+          // to script() which allocates handles.
+          if ((function.token_pos() == start_pos)
+              && (function.end_token_pos() == end_pos)
+              && (function.script() == script.raw())) {
+            function_list->Add(function);
+            if (function.HasImplicitClosureFunction()) {
+              function = function.ImplicitClosureFunction();
+              function_list->Add(function);
+            }
+          }
+        }
+      }
+      closures = cls.closures();
+      if (!closures.IsNull()) {
+        const intptr_t num_closures = closures.Length();
+        for (intptr_t pos = 0; pos < num_closures; pos++) {
+          function ^= closures.At(pos);
+          ASSERT(!function.IsNull());
+          if ((function.token_pos() == start_pos)
+              && (function.end_token_pos() == end_pos)
+              && (function.script() == script.raw())) {
+            function_list->Add(function);
+            if (function.HasImplicitClosureFunction()) {
+              function = function.ImplicitClosureFunction();
+              function_list->Add(function);
+            }
+          }
+        }
+      }
+    }
+  }
+}
+
+
+static void SelectBestFit(Function* best_fit, Function* func) {
+  if (best_fit->IsNull()) {
+    *best_fit = func->raw();
+  }
+  if (func->token_pos() > best_fit->token_pos()) {
+    if (func->end_token_pos() <= best_fit->end_token_pos()) {
+      // func is contained within best_fit. Select it even if it
+      // has not been compiled yet.
+      *best_fit = func->raw();
+      if (func->HasImplicitClosureFunction()) {
+        *func = func->ImplicitClosureFunction();
+        if (func->HasCode()) {
+          *best_fit = func->raw();
+        }
+      }
+    }
+  } else if ((func->token_pos() == best_fit->token_pos())
+      && (func->end_token_pos() == best_fit->end_token_pos())
+      && func->HasCode()) {
+    // If func covers the same range, it is considered a better fit if
+    // it has been compiled.
+    *best_fit = func->raw();
+  }
+}
+
+
+RawFunction* Debugger::FindBestFit(const Script& script,
+                                   intptr_t token_pos) {
+  Class& cls = Class::Handle(isolate_);
+  Array& functions = Array::Handle(isolate_);
+  GrowableObjectArray& closures = GrowableObjectArray::Handle(isolate_);
+  Function& function = Function::Handle(isolate_);
+  Function& best_fit = Function::Handle(isolate_);
+
+  const ClassTable& class_table = *isolate_->class_table();
+  const intptr_t num_classes = class_table.NumCids();
+  for (intptr_t i = 1; i < num_classes; i++) {
+    if (class_table.HasValidClassAt(i)) {
+      cls = class_table.At(i);
+      // Note: we need to check the functions of this class even if
+      // the class is defined in a differenct 'script'. There could
+      // be mixin functions from the given script in this class.
+      functions = cls.functions();
+      if (!functions.IsNull()) {
+        const intptr_t num_functions = functions.Length();
+        for (intptr_t pos = 0; pos < num_functions; pos++) {
+          function ^= functions.At(pos);
+          ASSERT(!function.IsNull());
+          if (FunctionContains(function, script, token_pos)) {
+            SelectBestFit(&best_fit, &function);
+          }
+        }
+      }
+
+      closures = cls.closures();
+      if (!closures.IsNull()) {
+        const intptr_t num_closures = closures.Length();
+        for (intptr_t pos = 0; pos < num_closures; pos++) {
+          function ^= closures.At(pos);
+          ASSERT(!function.IsNull());
+          if (FunctionContains(function, script, token_pos)) {
+            SelectBestFit(&best_fit, &function);
+          }
+        }
+      }
+    }
+  }
+  return best_fit.raw();
+}
+
+
+SourceBreakpoint* Debugger::SetBreakpoint(const Script& script,
+                                          intptr_t token_pos) {
+  Function& func = Function::Handle(isolate_);
+  func = FindBestFit(script, token_pos);
+  if (func.IsNull()) {
     return NULL;
   }
-  intptr_t breakpoint_pos = -1;
-  Function& closure = Function::Handle(isolate_);
-  if (target_function.HasImplicitClosureFunction()) {
-    // There is a closurized version of this function.
-    closure = target_function.ImplicitClosureFunction();
-  }
-  // Determine actual breakpoint location if the function or an
-  // implicit closure of the function has been compiled already.
-  if (target_function.HasCode()) {
+  if (!func.IsNull() && func.HasCode()) {
+    // A function containing this breakpoint location has already
+    // been compiled. We can resolve the breakpoint now.
     DeoptimizeWorld();
-    ASSERT(!target_function.HasOptimizedCode());
-    breakpoint_pos =
-        ResolveBreakpointPos(target_function, first_token_pos, last_token_pos);
-  } else if (!closure.IsNull() && closure.HasCode()) {
-    DeoptimizeWorld();
-    ASSERT(!closure.HasOptimizedCode());
-    breakpoint_pos =
-        ResolveBreakpointPos(closure, first_token_pos, last_token_pos);
-  } else {
-    // This function has not been compiled yet. Set a pending
-    // breakpoint to be resolved later.
-    SourceBreakpoint* source_bpt =
-        GetSourceBreakpoint(target_function, first_token_pos);
-    if (source_bpt != NULL) {
-      // A pending source breakpoint for this uncompiled location
-      // already exists.
-      if (FLAG_verbose_debug) {
-        OS::Print("Pending breakpoint for uncompiled function"
-                  " '%s' at line %" Pd " already exists\n",
-                  target_function.ToFullyQualifiedCString(),
-                  source_bpt->LineNumber());
-      }
-      return source_bpt;
-    }
-    source_bpt =
-        new SourceBreakpoint(nextId(), target_function, first_token_pos);
-    RegisterSourceBreakpoint(source_bpt);
-    if (FLAG_verbose_debug) {
-      OS::Print("Registering pending breakpoint for "
-                "uncompiled function '%s' at line %" Pd "\n",
-                target_function.ToFullyQualifiedCString(),
-                source_bpt->LineNumber());
-    }
-    source_bpt->Enable();
-    return source_bpt;
-  }
-  ASSERT(breakpoint_pos != -1);
-  SourceBreakpoint* source_bpt =
-      GetSourceBreakpoint(target_function, breakpoint_pos);
-  if (source_bpt != NULL) {
-    // A source breakpoint for this location already exists.
-    return source_bpt;
-  }
-  source_bpt = new SourceBreakpoint(nextId(), target_function, breakpoint_pos);
-  RegisterSourceBreakpoint(source_bpt);
-  if (target_function.HasCode()) {
-    MakeCodeBreakpointsAt(target_function, breakpoint_pos, source_bpt);
-  }
-  if (!closure.IsNull() && closure.HasCode()) {
-    MakeCodeBreakpointsAt(closure, breakpoint_pos, source_bpt);
-  }
-  source_bpt->Enable();
-  SignalBpResolved(source_bpt);
-  return source_bpt;
-}
-
-
+    intptr_t breakpoint_pos = ResolveBreakpointPos(func, token_pos);
+    if (breakpoint_pos >= 0) {
+      SourceBreakpoint* bpt = GetSourceBreakpoint(script, breakpoint_pos);
+      if (bpt != NULL) {
+        // A source breakpoint for this location already exists.
+        return bpt;
+      }
+      bpt = new SourceBreakpoint(nextId(), script, token_pos);
+      bpt->SetResolved(func, breakpoint_pos);
+      RegisterSourceBreakpoint(bpt);
+      // There may be more than one function object for a given function
+      // in source code. There may be implicit closure functions, and
+      // there may be copies of mixin functions. Collect all functions whose
+      // source code range matches exactly the best fit function we
+      // found.
+      GrowableObjectArray& functions =
+          GrowableObjectArray::Handle(GrowableObjectArray::New());
+      FindEquivalentFunctions(script,
+                              func.token_pos(),
+                              func.end_token_pos(),
+                              &functions);
+      const intptr_t num_functions = functions.Length();
+      // We must have found at least one function: func.
+      ASSERT(num_functions > 0);
+      // Create code breakpoints for all compiled functions we found.
+      for (intptr_t i = 0; i < num_functions; i++) {
+        func ^= functions.At(i);
+        if (func.HasCode()) {
+          MakeCodeBreakpointsAt(func, bpt);
+        }
+      }
+      bpt->Enable();
+      SignalBpResolved(bpt);
+      return bpt;
+    }
+  }
+  // There is no compiled function at this token position.
+  // Register an unresolved breakpoint.
+  if (FLAG_verbose_debug && !func.IsNull()) {
+    intptr_t line_number;
+    script.GetTokenLocation(token_pos, &line_number, NULL);
+    OS::Print("Registering pending breakpoint for "
+              "uncompiled function '%s' at line %" Pd "\n",
+              func.ToFullyQualifiedCString(),
+              line_number);
+  }
+  SourceBreakpoint* bpt = GetSourceBreakpoint(script, token_pos);
+  if (bpt == NULL) {
+    bpt = new SourceBreakpoint(nextId(), script, token_pos);
+  }
+  RegisterSourceBreakpoint(bpt);
+  bpt->Enable();
+  return bpt;
+}
+
+
 // Synchronize the enabled/disabled state of all code breakpoints
 // associated with the source breakpoint bpt.
 void Debugger::SyncBreakpoint(SourceBreakpoint* bpt) {
   CodeBreakpoint* cbpt = code_breakpoints_;
   while (cbpt != NULL) {
     if (bpt == cbpt->src_bpt()) {
       if (bpt->IsEnabled()) {
         cbpt->Enable();
       } else {
         cbpt->Disable();
@@ skipping 10 matching lines @@
     const Function& closure_func =
         Function::Handle(target_function.ImplicitClosureFunction());
     InstrumentForStepping(closure_func);
   }
 }
 
 
 SourceBreakpoint* Debugger::SetBreakpointAtEntry(
       const Function& target_function) {
   ASSERT(!target_function.IsNull());
-  return SetBreakpoint(target_function,
-                       target_function.token_pos(),
-                       target_function.end_token_pos());
+  const Script& script = Script::Handle(target_function.script());
+  return SetBreakpoint(script, target_function.token_pos());
 }
 
 
 SourceBreakpoint* Debugger::SetBreakpointAtLine(const String& script_url,
                                                 intptr_t line_number) {
   Library& lib = Library::Handle(isolate_);
   Script& script = Script::Handle(isolate_);
   const GrowableObjectArray& libs =
       GrowableObjectArray::Handle(isolate_->object_store()->libraries());
   for (intptr_t i = 0; i < libs.Length(); i++) {
@@ skipping 13 matching lines @@
   intptr_t first_token_idx, last_token_idx;
   script.TokenRangeAtLine(line_number, &first_token_idx, &last_token_idx);
   if (first_token_idx < 0) {
     // Script does not contain the given line number.
     if (FLAG_verbose_debug) {
       OS::Print("Script '%s' does not contain line number %" Pd "\n",
                 script_url.ToCString(), line_number);
     }
     return NULL;
   } else if (last_token_idx < 0) {
-    // Line does not contain any tokens. first_token_index is the first
-    // token after the given line. We check whether that token is
-    // part of a function.
-    last_token_idx = first_token_idx;
-  }
-
-  Function& func = Function::Handle(isolate_);
-  while (first_token_idx <= last_token_idx) {
-    func = lib.LookupFunctionInScript(script, first_token_idx);
-    if (!func.IsNull()) {
-      break;
-    }
-    first_token_idx++;
-  }
-  if (func.IsNull()) {
+    // Line does not contain any tokens.
     if (FLAG_verbose_debug) {
       OS::Print("No executable code at line %" Pd " in '%s'\n",
                 line_number, script_url.ToCString());
     }
     return NULL;
   }
-  if (last_token_idx < 0) {
-    // The token at first_token_index is past the requested source line.
-    // Set the breakpoint at the closest position after that line.
-    last_token_idx = func.end_token_pos();
+
+  SourceBreakpoint* bpt = NULL;
+  ASSERT(first_token_idx <= last_token_idx);
+  while ((bpt == NULL) && (first_token_idx <= last_token_idx)) {
+    bpt = SetBreakpoint(script, first_token_idx);
+    first_token_idx++;
   }
-  return SetBreakpoint(func, first_token_idx, last_token_idx);
+  if ((bpt == NULL) && FLAG_verbose_debug) {
+    OS::Print("No executable code at line %" Pd " in '%s'\n",
+                line_number, script_url.ToCString());
+  }
+  return bpt;
 }
 
 
 intptr_t Debugger::CacheObject(const Object& obj) {
   ASSERT(obj_cache_ != NULL);
   return obj_cache_->AddObject(obj);
 }
 
 
 bool Debugger::IsValidObjectId(intptr_t obj_id) {
@@ skipping 371 matching lines @@
   // This port will be used as a unique ID to represet the isolate in the
   // debugger wire protocol messages.
   isolate_id_ = isolate->main_port();
   initialized_ = true;
 
   // Signal isolate creation event.
   SignalIsolateEvent(Debugger::kIsolateCreated);
 }
 
 
-static RawFunction* GetOriginalFunction(const Function& func) {
-  if (func.IsClosureFunction()) {
-    // Local functions (closures) in mixin functions do not have
-    // an original function they were cloned from.
-    // Note: this is a problem when a breakpoint is set in a mixed-in
-    // closure. The breakpoint is linked to the closure attached to the
-    // mixin application class, not the mixin class. When the same
-    // closure is compiled for another mixin application class, we
-    // don't find the breakpoint since we'll be looking in the
-    // mixin class.
-    return func.raw();
+// Return innermost closure contained in 'function' that contains
+// the given token position.
+RawFunction* Debugger::FindInnermostClosure(const Function& function,
+                                            intptr_t token_pos) {
+  const Class& owner = Class::Handle(isolate_, function.Owner());
+  if (owner.closures() == GrowableObjectArray::null()) {
+    return Function::null();
   }
-  const Class& origin_class = Class::Handle(func.origin());
-  if (origin_class.is_patch()) {
-    // Patched functions from patch classes are removed from the
-    // function array of the patch class, so we will not find an
-    // original function object.
-    return func.raw();
-  }
-  const Array& functions = Array::Handle(origin_class.functions());
-  Object& orig_func = Object::Handle();
-  for (intptr_t i = 0; i < functions.Length(); i++) {
-    orig_func = functions.At(i);
-    // Function names are symbols, so we can compare the raw pointers.
-    if (func.name() == Function::Cast(orig_func).name()) {
-      return Function::Cast(orig_func).raw();
+  // Note that we need to check that the closure is in the same
+  // script as the outer function. We could have closures originating
+  // in mixin classes whose source code is contained in a different
+  // script.
+  const Script& outer_origin = Script::Handle(isolate_, function.script());
+  const GrowableObjectArray& closures =
+     GrowableObjectArray::Handle(isolate_, owner.closures());
+  const intptr_t num_closures = closures.Length();
+  Function& closure = Function::Handle(isolate_);
+  Function& best_fit = Function::Handle(isolate_);
+  for (intptr_t i = 0; i < num_closures; i++) {
+    closure ^= closures.At(i);
+    if ((function.token_pos() < closure.token_pos()) &&
+        (closure.end_token_pos() < function.end_token_pos()) &&
+        (closure.token_pos() <= token_pos) &&
+        (token_pos <= closure.end_token_pos()) &&
+        (closure.script() == outer_origin.raw())) {
+      SelectBestFit(&best_fit, &closure);
     }
   }
-  // Uncommon case: not a mixin function.
-  ASSERT(!Class::Handle(func.Owner()).IsMixinApplication());
-  return func.raw();
+  return best_fit.raw();
 }
 
 
 void Debugger::NotifyCompilation(const Function& func) {
   if (src_breakpoints_ == NULL) {
     // Return with minimal overhead if there are no breakpoints.
     return;
   }
-  Function& lookup_function = Function::Handle(func.raw());
-  if (func.IsImplicitClosureFunction()) {
-    // If the newly compiled function is a an implicit closure (a closure that
-    // was formed by assigning a static or instance method to a function
-    // object), we need to use the closure's parent function to see whether
-    // there are any breakpoints. The parent function is the actual method on
-    // which the user sets breakpoints.
-    lookup_function = func.parent_function();
-    ASSERT(!lookup_function.IsNull());
-  }
-  if (lookup_function.Owner() != lookup_function.origin()) {
-    // This is a cloned function from a mixin class. If a breakpoint
-    // was set in this function, it is registered using the function
-    // of the origin class.
-    lookup_function = GetOriginalFunction(lookup_function);
-  }
-  SourceBreakpoint* bpt = src_breakpoints_;
-  while (bpt != NULL) {
-    if (lookup_function.raw() == bpt->function()) {
-      // Check if the breakpoint is inside a closure or local function
-      // within the newly compiled function. Note that we must look
-      // in the owner class of the function that just got compiled
-      // (i.e. func), not the owner class of the function we use to
-      // record the breakpoint (lookup_function).
-      Class& owner = Class::Handle(func.Owner());
-      Function& closure =
-          Function::Handle(owner.LookupClosureFunction(bpt->token_pos()));
-      if (!closure.IsNull() && (closure.raw() != lookup_function.raw())) {
+  // Iterate over all source breakpoints to check whether breakpoints
+  // need to be set in the newly compiled function.
+  Script& script = Script::Handle(isolate_);
+  for (SourceBreakpoint* bpt = src_breakpoints_;
+       bpt != NULL;
+       bpt = bpt->next()) {
+       script = bpt->script();
+    if (FunctionContains(func, script, bpt->token_pos())) {
+      Function& inner_function = Function::Handle(isolate_);
+      inner_function = FindInnermostClosure(func, bpt->token_pos());
+      if (!inner_function.IsNull()) {
+        // The local function of a function we just compiled cannot
+        // be compiled already.
+        ASSERT(!inner_function.HasCode());
         if (FLAG_verbose_debug) {
-          OS::Print("Resetting pending breakpoint to function %s\n",
-                    closure.ToFullyQualifiedCString());
+          OS::Print("Pending BP remains unresolved in inner function '%s'\n",
+                    inner_function.ToFullyQualifiedCString());
         }
-        bpt->set_function(closure);
-      } else {
+        continue;
+      }
+
+      // TODO(hausner): What should we do if function is optimized?
+      // Can we deoptimize the function?
+      ASSERT(!func.HasOptimizedCode());
+
+      // There is no local function within func that contains the
+      // breakpoint token position. Resolve the breakpoint if necessary
+      // and set the code breakpoints.
+      if (!bpt->IsResolved()) {
+        // Resolve source breakpoint in the newly compiled function.
+        intptr_t bp_pos = ResolveBreakpointPos(func, bpt->token_pos());
+        if (bp_pos < 0) {
+          if (FLAG_verbose_debug) {
+            OS::Print("Failed resolving breakpoint for function '%s'\n",
+                      String::Handle(func.name()).ToCString());
+          }
+          continue;
+        }
+        intptr_t requested_pos = bpt->token_pos();
+        bpt->SetResolved(func, bp_pos);
         if (FLAG_verbose_debug) {
-          OS::Print("Enable pending breakpoint for function '%s'\n",
-                    String::Handle(lookup_function.name()).ToCString());
+          OS::Print("Resolved BP %" Pd " to pos %" Pd ", line %" Pd ", "
+                    "function '%s' (requested pos %" Pd ")\n",
+                    bpt->id(),
+                    bpt->token_pos(),
+                    bpt->LineNumber(),
+                    func.ToFullyQualifiedCString(),
+                    requested_pos);
         }
-        const Script& script= Script::Handle(func.script());
-        intptr_t first_pos, last_pos;
-        script.TokenRangeAtLine(bpt->LineNumber(), &first_pos, &last_pos);
-        intptr_t bp_pos =
-            ResolveBreakpointPos(func, bpt->token_pos(), last_pos);
-        bpt->set_token_pos(bp_pos);
-        MakeCodeBreakpointsAt(func, bp_pos, bpt);
         SignalBpResolved(bpt);
       }
-      bpt->Enable();  // Enables the code breakpoint as well.
+      ASSERT(bpt->IsResolved());
+      if (FLAG_verbose_debug) {
+        OS::Print("Setting breakpoint %" Pd " at line %" Pd " for %s '%s'\n",
+                  bpt->id(),
+                  bpt->LineNumber(),
+                  func.IsClosureFunction() ? "closure" : "function",
+                  String::Handle(func.name()).ToCString());
+      }
+      MakeCodeBreakpointsAt(func, bpt);
     }
-    bpt = bpt->next();
   }
 }
 
 
 CodeBreakpoint* Debugger::GetCodeBreakpoint(uword breakpoint_address) {
   CodeBreakpoint* bpt = code_breakpoints_;
   while (bpt != NULL) {
     if (bpt->pc() == breakpoint_address) {
       return bpt;
     }
@@ skipping 73 matching lines @@
       temp_bpt->Disable();
       delete temp_bpt;
     } else {
       prev_bpt = curr_bpt;
       curr_bpt = curr_bpt->next();
     }
   }
 }
 
 
-SourceBreakpoint* Debugger::GetSourceBreakpoint(const Function& func,
+SourceBreakpoint* Debugger::GetSourceBreakpoint(const Script& script,
                                                 intptr_t token_pos) {
   SourceBreakpoint* bpt = src_breakpoints_;
   while (bpt != NULL) {
-    if ((bpt->function() == func.raw()) &&
-        (bpt->token_pos() == token_pos)) {
+    if ((bpt->script_ == script.raw()) && (bpt->token_pos_ == token_pos)) {
       return bpt;
     }
     bpt = bpt->next();
   }
   return NULL;
 }
 
 
 SourceBreakpoint* Debugger::GetBreakpointById(intptr_t id) {
   SourceBreakpoint* bpt = src_breakpoints_;
@@ skipping 14 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart