Fixes a problem with the recovery of contexts in the debugger at closure calls.

runtime/vm/stub_code_ia32.cc

 // Copyright (c) 2013, 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/globals.h"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/instructions.h"
 #include "vm/heap.h"
 #include "vm/object_store.h"
 #include "vm/resolver.h"
 #include "vm/scavenger.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/tags.h"
 
 
 #define __ assembler->
 
 namespace dart {
 
 DEFINE_FLAG(bool, inline_alloc, true, "Inline allocation of objects.");
 DEFINE_FLAG(bool, use_slow_path, false,
     "Set to true for debugging & verifying the slow paths.");
 DECLARE_FLAG(bool, trace_optimized_ic_calls);
+DEFINE_FLAG(bool, verify_incoming_contexts, false, "");
 
 
 // Input parameters:
 //   ESP : points to return address.
 //   ESP + 4 : address of last argument in argument array.
 //   ESP + 4*EDX : address of first argument in argument array.
 //   ESP + 4*EDX + 4 : address of return value.
 //   ECX : address of the runtime function to call.
 //   EDX : number of arguments to the call.
 // Must preserve callee saved registers EDI and EBX.
 void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   const intptr_t isolate_offset = NativeArguments::isolate_offset();
   const intptr_t argc_tag_offset = NativeArguments::argc_tag_offset();
   const intptr_t argv_offset = NativeArguments::argv_offset();
   const intptr_t retval_offset = NativeArguments::retval_offset();
 
   __ EnterFrame(0);
 
   // Load current Isolate pointer from Context structure into EAX.
   __ movl(EAX, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
   __ movl(Address(EAX, Isolate::top_exit_frame_info_offset()), ESP);
 
+#if defined(DEBUG)
+  if (FLAG_verify_incoming_contexts) {
+    Label ok;
+    // Check that the isolate's saved ctx is null.
+    const Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    __ cmpl(Address(EAX, Isolate::top_context_offset()), raw_null);
+    __ j(EQUAL, &ok, Assembler::kNearJump);
+    __ Stop("Found non-null incoming top context: call to runtime stub");
+    __ Bind(&ok);
+  }
+#endif
+
   // Save current Context pointer into Isolate structure.
   __ movl(Address(EAX, Isolate::top_context_offset()), CTX);
 
   // Cache Isolate pointer into CTX while executing runtime code.
   __ movl(CTX, EAX);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movl(EAX, Address(CTX, Isolate::vm_tag_offset()));
@@ skipping 88 matching lines @@
 
   __ EnterFrame(0);
 
   // Load current Isolate pointer from Context structure into EDI.
   __ movl(EDI, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to dart VM code.
   __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), ESP);
 
+#if defined(DEBUG)
+  if (FLAG_verify_incoming_contexts) {
+    Label ok;
+    // Check that the isolate's saved ctx is null.
+    const Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    __ cmpl(Address(EDI, Isolate::top_context_offset()), raw_null);
+    __ j(EQUAL, &ok, Assembler::kNearJump);
+    __ Stop("Found non-null incoming top context: "
+            "call to native c function stub");
+    __ Bind(&ok);
+  }
+#endif
+
   // Save current Context pointer into Isolate structure.
   __ movl(Address(EDI, Isolate::top_context_offset()), CTX);
 
   // Cache Isolate pointer into CTX while executing native code.
   __ movl(CTX, EDI);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movl(EDI, Address(CTX, Isolate::vm_tag_offset()));
@@ skipping 80 matching lines @@
 
   __ EnterFrame(0);
 
   // Load current Isolate pointer from Context structure into EDI.
   __ movl(EDI, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to dart VM code.
   __ movl(Address(EDI, Isolate::top_exit_frame_info_offset()), ESP);
 
+#if defined(DEBUG)
+  if (FLAG_verify_incoming_contexts) {
+    Label ok;
+    // Check that the isolate's saved ctx is null.
+    const Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    __ cmpl(Address(EDI, Isolate::top_context_offset()), raw_null);
+    __ j(EQUAL, &ok, Assembler::kNearJump);
+    __ Stop("Found non-null incoming top context: "
+            "call to bootstrap c function stub");
+    __ Bind(&ok);
+  }
+#endif
+
   // Save current Context pointer into Isolate structure.
   __ movl(Address(EDI, Isolate::top_context_offset()), CTX);
 
   // Cache Isolate pointer into CTX while executing native code.
   __ movl(CTX, EDI);
 
 #if defined(DEBUG)
   { Label ok;
     // Check that we are always entering from Dart code.
     __ movl(EDI, Address(CTX, Isolate::vm_tag_offset()));
@@ skipping 560 matching lines @@
   // Note that VisitObjectPointers will find this saved Context pointer during
   // GC marking, since it traverses any information between SP and
   // FP - kExitLinkSlotFromEntryFp.
   // EntryFrame::SavedContext reads the context saved in this frame.
   // The constant kSavedContextSlotFromEntryFp must be kept in sync with
   // the code below.
   ASSERT(kSavedContextSlotFromEntryFp == -6);
   __ movl(ECX, Address(EDI, Isolate::top_context_offset()));
   __ pushl(ECX);
 
+  // TODO(turnidge): This code should probably be emitted all the time
+  // on all architectures but I am leaving it under DEBUG/flag for
+  // now.
+#if defined(DEBUG)
+  if (FLAG_verify_incoming_contexts) {
+    // Clear Context pointer in Isolate structure.
+    const Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    __ movl(Address(EDI, Isolate::top_context_offset()), raw_null);
+  }
+#endif
+
   // Load arguments descriptor array into EDX.
   __ movl(EDX, Address(EBP, kArgumentsDescOffset));
   __ movl(EDX, Address(EDX, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load number of arguments into EBX.
   __ movl(EBX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(EBX);
 
   // Set up arguments for the dart call.
   Label push_arguments;
@@ skipping 1087 matching lines @@
   const Register temp = ECX;
   __ movl(left, Address(ESP, 2 * kWordSize));
   __ movl(right, Address(ESP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32