Instrument debugger to track down stack trace problems

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 349 matching lines @@
 RawContext* ActivationFrame::GetSavedCurrentContext() {
   GetVarDescriptors();
   intptr_t var_desc_len = var_descriptors_.Length();
   for (int i = 0; i < var_desc_len; i++) {
     RawLocalVarDescriptors::VarInfo var_info;
     var_descriptors_.GetInfo(i, &var_info);
     if (var_info.kind == RawLocalVarDescriptors::kSavedCurrentContext) {
       return reinterpret_cast<RawContext*>(GetLocalVarValue(var_info.index));
     }
   }
-  UNREACHABLE();
   return Context::null();
 }
 
 
 ActivationFrame* DebuggerStackTrace::GetHandlerFrame(
     const Instance& exc_obj) const {
   ExceptionHandlers& handlers = ExceptionHandlers::Handle();
   Array& handled_types = Array::Handle();
   AbstractType& type = Type::Handle();
   const TypeArguments& no_instantiator = TypeArguments::Handle();
@@ skipping 529 matching lines @@
                                                         frame->fp(),
                                                         frame->sp(),
                                                         code);
       // If this activation frame called a closure, the function has
       // saved its context before the call.
       if (stack_trace->Length() > 0) {
         ActivationFrame* callee_frame =
             stack_trace->ActivationFrameAt(stack_trace->Length() - 1);
         if (callee_frame->function().IsClosureFunction()) {
           ctx = activation->GetSavedCurrentContext();
+          if (FLAG_verbose_debug && ctx.IsNull()) {
+            const Function& caller = activation->function();
+            const Function& callee = callee_frame->function();
+            const Script& script =
+                Script::Handle(Class::Handle(caller.Owner()).script());
+            intptr_t line, col;
+            script.GetTokenLocation(activation->TokenPos(), &line, &col);
+            printf("CollectStackTrace error: no saved context in function "
+                "'%s' which calls closure '%s' "
+                " in line %"Pd" column %"Pd"\n",
+                caller.ToFullyQualifiedCString(),
+                callee.ToFullyQualifiedCString(),
+                line, col);
+          }
+          ASSERT(!ctx.IsNull());
         }
       }
       if (optimized_frame_found || code.is_optimized()) {
         // Set context to null, to avoid returning bad context variable values.
         activation->SetContext(Context::Handle());
         optimized_frame_found = true;
       } else {
         activation->SetContext(ctx);
       }
       stack_trace->AddActivation(activation);
@@ skipping 733 matching lines @@
     }
     bpt = bpt->next();
   }
   return NULL;
 }
 
 
 // Remove and delete the source breakpoint bpt and its associated
 // code breakpoints.
 void Debugger::RemoveBreakpoint(intptr_t bp_id) {
-  ASSERT(src_breakpoints_ != NULL);
   SourceBreakpoint* prev_bpt = NULL;
   SourceBreakpoint* curr_bpt = src_breakpoints_;
   while (curr_bpt != NULL) {
     if (curr_bpt->id() == bp_id) {
       if (prev_bpt == NULL) {
         src_breakpoints_ = src_breakpoints_->next();
       } else {
         prev_bpt->set_next(curr_bpt->next());
       }
       // Remove references from code breakpoints to this source breakpoint,
@@ skipping 84 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart