sdk/runtime/vm/exceptions.cc

// Copyright (c) 2011, 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/exceptions.h"

#include "vm/dart_api_impl.h"
#include "vm/dart_entry.h"
#include "vm/debugger.h"
#include "vm/flags.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/stack_frame.h"
#include "vm/stub_code.h"
#include "vm/symbols.h"

namespace dart {

DEFINE_FLAG(bool, print_stacktrace_at_throw, false,
            "Prints a stack trace everytime a throw occurs.");
DEFINE_FLAG(bool, heap_profile_out_of_memory, false,
            "Writes a heap profile on unhandled out-of-memory exceptions.");
DEFINE_FLAG(bool, verbose_stacktrace, false,
    "Stack traces will include methods marked invisible.");

const char* Exceptions::kCastErrorDstName = "type cast";


class StacktraceBuilder : public ValueObject {
 public:
  StacktraceBuilder() { }
  virtual ~StacktraceBuilder() { }

  virtual void AddFrame(const Function& func,
                        const Code& code,
                        const Smi& offset) = 0;
};


class RegularStacktraceBuilder : public StacktraceBuilder {
 public:
  RegularStacktraceBuilder()
      : func_list_(GrowableObjectArray::Handle(GrowableObjectArray::New())),
        code_list_(GrowableObjectArray::Handle(GrowableObjectArray::New())),
        pc_offset_list_(
            GrowableObjectArray::Handle(GrowableObjectArray::New())) { }
  ~RegularStacktraceBuilder() { }

  const GrowableObjectArray& func_list() const { return func_list_; }
  const GrowableObjectArray& code_list() const { return code_list_; }
  const GrowableObjectArray& pc_offset_list() const { return pc_offset_list_; }

  virtual void AddFrame(const Function& func,
                        const Code& code,
                        const Smi& offset) {
    func_list_.Add(func);
    code_list_.Add(code);
    pc_offset_list_.Add(offset);
  }

 private:
  const GrowableObjectArray& func_list_;
  const GrowableObjectArray& code_list_;
  const GrowableObjectArray& pc_offset_list_;

  DISALLOW_COPY_AND_ASSIGN(RegularStacktraceBuilder);
};


class PreallocatedStacktraceBuilder : public StacktraceBuilder {
 public:
  explicit PreallocatedStacktraceBuilder(const Stacktrace& stacktrace)
      : stacktrace_(stacktrace),
        cur_index_(0) {
    ASSERT(stacktrace_.raw() ==
           Isolate::Current()->object_store()->preallocated_stack_trace());
  }
  ~PreallocatedStacktraceBuilder() { }

  virtual void AddFrame(const Function& func,
                        const Code& code,
                        const Smi& offset);

 private:
  static const int kNumTopframes = 3;

  const Stacktrace& stacktrace_;
  intptr_t cur_index_;

  DISALLOW_COPY_AND_ASSIGN(PreallocatedStacktraceBuilder);
};


void PreallocatedStacktraceBuilder::AddFrame(const Function& func,
                                             const Code& code,
                                             const Smi& offset) {
  if (cur_index_ >= Stacktrace::kPreallocatedStackdepth) {
    // The number of frames is overflowing the preallocated stack trace object.
    Function& frame_func = Function::Handle();
    Code& frame_code = Code::Handle();
    Smi& frame_offset = Smi::Handle();
    intptr_t start = Stacktrace::kPreallocatedStackdepth - (kNumTopframes - 1);
    intptr_t null_slot = start - 2;
    // Add an empty slot to indicate the overflow so that the toString
    // method can account for the overflow.
    if (stacktrace_.FunctionAtFrame(null_slot) != Function::null()) {
      stacktrace_.SetFunctionAtFrame(null_slot, frame_func);
      stacktrace_.SetCodeAtFrame(null_slot, frame_code);
    }
    // Move frames one slot down so that we can accomadate the new frame.
    for (intptr_t i = start; i < Stacktrace::kPreallocatedStackdepth; i++) {
      intptr_t prev = (i - 1);
      frame_func = stacktrace_.FunctionAtFrame(i);
      frame_code = stacktrace_.CodeAtFrame(i);
      frame_offset = stacktrace_.PcOffsetAtFrame(i);
      stacktrace_.SetFunctionAtFrame(prev, frame_func);
      stacktrace_.SetCodeAtFrame(prev, frame_code);
      stacktrace_.SetPcOffsetAtFrame(prev, frame_offset);
    }
    cur_index_ = (Stacktrace::kPreallocatedStackdepth - 1);
  }
  stacktrace_.SetFunctionAtFrame(cur_index_, func);
  stacktrace_.SetCodeAtFrame(cur_index_, code);
  stacktrace_.SetPcOffsetAtFrame(cur_index_, offset);
  cur_index_ += 1;
}


static bool ShouldShowFunction(const Function& function) {
  if (FLAG_verbose_stacktrace) {
    return true;
  }
  return function.is_visible();
}


// Iterate through the stack frames and try to find a frame with an
// exception handler. Once found, set the pc, sp and fp so that execution
// can continue in that frame.
static bool FindExceptionHandler(uword* handler_pc,
                                 uword* handler_sp,
                                 uword* handler_fp,
                                 StacktraceBuilder* builder) {
  StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
  StackFrame* frame = frames.NextFrame();
  ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
  Function& func = Function::Handle();
  Code& code = Code::Handle();
  Smi& offset = Smi::Handle();
  while (!frame->IsEntryFrame()) {
    if (frame->IsDartFrame()) {
      code = frame->LookupDartCode();
      if (code.is_optimized()) {
        // For optimized frames, extract all the inlined functions if any
        // into the stack trace.
        for (InlinedFunctionsIterator it(frame); !it.Done(); it.Advance()) {
          func = it.function();
          code = it.code();
          uword pc = it.pc();
          ASSERT(pc != 0);
          ASSERT(code.EntryPoint() <= pc);
          ASSERT(pc < (code.EntryPoint() + code.Size()));
          if (ShouldShowFunction(func)) {
            offset = Smi::New(pc - code.EntryPoint());
            builder->AddFrame(func, code, offset);
          }
        }
      } else {
        offset = Smi::New(frame->pc() - code.EntryPoint());
        func = code.function();
        if (ShouldShowFunction(func)) {
          builder->AddFrame(func, code, offset);
        }
      }
      if (frame->FindExceptionHandler(handler_pc)) {
        *handler_sp = frame->sp();
        *handler_fp = frame->fp();
        return true;
      }
    }
    frame = frames.NextFrame();
    ASSERT(frame != NULL);
  }
  ASSERT(frame->IsEntryFrame());
  *handler_pc = frame->pc();
  *handler_sp = frame->sp();
  *handler_fp = frame->fp();
  return false;
}


static void FindErrorHandler(uword* handler_pc,
                             uword* handler_sp,
                             uword* handler_fp) {
  // TODO(turnidge): Is there a faster way to get the next entry frame?
  StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
  StackFrame* frame = frames.NextFrame();
  ASSERT(frame != NULL);
  while (!frame->IsEntryFrame()) {
    frame = frames.NextFrame();
    ASSERT(frame != NULL);
  }
  ASSERT(frame->IsEntryFrame());
  *handler_pc = frame->pc();
  *handler_sp = frame->sp();
  *handler_fp = frame->fp();
}


static void JumpToHandler(uword program_counter,
                          uword stack_pointer,
                          uword frame_pointer,
                          RawObject* raw_exception,
                          RawObject* raw_stacktrace) {
#if defined(USING_SIMULATOR)
  // Unwinding of the C++ frames and destroying of their stack resources is done
  // by the simulator, because the target stack_pointer is a simulated stack
  // pointer and not the C++ stack pointer.

  // Continue simulating at the given pc in the given frame after setting up the
  // exception object in the kExceptionObjectReg register and the stacktrace
  // object (if not NULL) in the kStackTraceObjectReg register.
  Simulator::Current()->Longjmp(program_counter, stack_pointer, frame_pointer,
                                raw_exception, raw_stacktrace);
#else
  // Prepare for unwinding frames by destroying all the stack resources
  // in the previous frames.
  Isolate* isolate = Isolate::Current();
  while (isolate->top_resource() != NULL &&
         (reinterpret_cast<uword>(isolate->top_resource()) < stack_pointer)) {
    isolate->top_resource()->~StackResource();
  }

  // TODO(regis): Can we safely merge both stubs and pass NULL as
  // stacktrace_object in the case of an error handler?

  // A NULL raw_stacktrace indicates that we are jumping to an ErrorHandler,
  // rather than to an ExceptionHandler. TODO(regis): Merge these two cases.
  if (raw_stacktrace == NULL) {
    // Call a stub to set up the error object in kExceptionObjectReg and to
    // continue execution at the given pc in the given frame.
    typedef void (*ErrorHandler)(uword, uword, uword, RawObject*);
    ErrorHandler func = reinterpret_cast<ErrorHandler>(
        StubCode::JumpToErrorHandlerEntryPoint());
    func(program_counter, stack_pointer, frame_pointer, raw_exception);
  } else {
    // Call a stub to set up the exception object in kExceptionObjectReg,
    // to set up the stacktrace object in kStackTraceObjectReg, and to
    // continue execution at the given pc in the given frame.
    typedef void (*ExcpHandler)(uword, uword, uword, RawObject*, RawObject*);
    ExcpHandler func = reinterpret_cast<ExcpHandler>(
        StubCode::JumpToExceptionHandlerEntryPoint());
    func(program_counter, stack_pointer, frame_pointer,
         raw_exception, raw_stacktrace);
  }
#endif
  UNREACHABLE();
}


static void JumpToExceptionHandler(uword program_counter,
                                   uword stack_pointer,
                                   uword frame_pointer,
                                   const Instance& exception_object,
                                   const Instance& stacktrace_object) {
  // The no_gc StackResource is unwound through the tear down of
  // stack resources below.
  NoGCScope no_gc;
  RawObject* raw_exception = exception_object.raw();
  RawObject* raw_stacktrace = stacktrace_object.raw();

  JumpToHandler(program_counter, stack_pointer, frame_pointer,
                raw_exception, raw_stacktrace);

  UNREACHABLE();
}


static void JumpToErrorHandler(uword program_counter,
                               uword stack_pointer,
                               uword frame_pointer,
                               const Error& error_object) {
  // The no_gc StackResource is unwound through the tear down of
  // stack resources below.
  NoGCScope no_gc;
  ASSERT(!error_object.IsNull());
  RawObject* raw_error = error_object.raw();

  JumpToHandler(
      program_counter, stack_pointer, frame_pointer, raw_error, NULL);

  UNREACHABLE();
}


static void ThrowExceptionHelper(const Instance& incoming_exception,
                                 const Instance& existing_stacktrace) {
  bool use_preallocated_stacktrace = false;
  Isolate* isolate = Isolate::Current();
  Instance& exception = Instance::Handle(isolate, incoming_exception.raw());
  if (exception.IsNull()) {
    exception ^= Exceptions::Create(Exceptions::kNullThrown,
                                    Object::empty_array());
  } else if (exception.raw() == isolate->object_store()->out_of_memory() ||
             exception.raw() == isolate->object_store()->stack_overflow()) {
    use_preallocated_stacktrace = true;
  }
  uword handler_pc = 0;
  uword handler_sp = 0;
  uword handler_fp = 0;
  Stacktrace& stacktrace = Stacktrace::Handle(isolate);
  bool handler_exists = false;
  if (use_preallocated_stacktrace) {
    stacktrace ^= isolate->object_store()->preallocated_stack_trace();
    PreallocatedStacktraceBuilder frame_builder(stacktrace);
    handler_exists = FindExceptionHandler(&handler_pc,
                                          &handler_sp,
                                          &handler_fp,
                                          &frame_builder);
  } else {
    RegularStacktraceBuilder frame_builder;
    handler_exists = FindExceptionHandler(&handler_pc,
                                          &handler_sp,
                                          &handler_fp,
                                          &frame_builder);
    // TODO(5411263): At some point we can optimize by figuring out if a
    // stack trace is needed based on whether the catch code specifies a
    // stack trace object or there is a rethrow in the catch clause.
    if (frame_builder.pc_offset_list().Length() != 0) {
      // Create arrays for function, code and pc_offset triplet for each frame.
      const Array& func_array =
          Array::Handle(isolate, Array::MakeArray(frame_builder.func_list()));
      const Array& code_array =
          Array::Handle(isolate, Array::MakeArray(frame_builder.code_list()));
      const Array& pc_offset_array =
          Array::Handle(isolate,
                        Array::MakeArray(frame_builder.pc_offset_list()));
      if (existing_stacktrace.IsNull()) {
        stacktrace = Stacktrace::New(func_array, code_array, pc_offset_array);
      } else {
        stacktrace ^= existing_stacktrace.raw();
        stacktrace.Append(func_array, code_array, pc_offset_array);
        // Since we are re throwing and appending to the existing stack trace
        // we clear out the catch trace collected in the existing stack trace
        // as that trace will not be valid anymore.
        stacktrace.SetCatchStacktrace(Object::empty_array(),
                                      Object::empty_array(),
                                      Object::empty_array());
      }
    } else {
      stacktrace ^= existing_stacktrace.raw();
      // Since we are re throwing and appending to the existing stack trace
      // we clear out the catch trace collected in the existing stack trace
      // as that trace will not be valid anymore.
      stacktrace.SetCatchStacktrace(Object::empty_array(),
                                    Object::empty_array(),
                                    Object::empty_array());
    }
  }
  // We expect to find a handler_pc, if the exception is unhandled
  // then we expect to at least have the dart entry frame on the
  // stack as Exceptions::Throw should happen only after a dart
  // invocation has been done.
  ASSERT(handler_pc != 0);

  if (FLAG_print_stacktrace_at_throw) {
    OS::Print("Exception '%s' thrown:\n", exception.ToCString());
    OS::Print("%s\n", stacktrace.ToCString());
  }
  if (handler_exists) {
    // Found a dart handler for the exception, jump to it.
    JumpToExceptionHandler(handler_pc,
                           handler_sp,
                           handler_fp,
                           exception,
                           stacktrace);
  } else {
    if (FLAG_heap_profile_out_of_memory) {
      if (exception.raw() == isolate->object_store()->out_of_memory()) {
        isolate->heap()->ProfileToFile("out-of-memory");
      }
    }
    // No dart exception handler found in this invocation sequence,
    // so we create an unhandled exception object and return to the
    // invocation stub so that it returns this unhandled exception
    // object. The C++ code which invoked this dart sequence can check
    // and do the appropriate thing (rethrow the exception to the
    // dart invocation sequence above it, print diagnostics and terminate
    // the isolate etc.).
    const UnhandledException& unhandled_exception = UnhandledException::Handle(
        UnhandledException::New(exception, stacktrace));
    JumpToErrorHandler(handler_pc, handler_sp, handler_fp, unhandled_exception);
  }
  UNREACHABLE();
}


// Static helpers for allocating, initializing, and throwing an error instance.

// Return the script of the Dart function that called the native entry or the
// runtime entry. The frame iterator points to the callee.
RawScript* Exceptions::GetCallerScript(DartFrameIterator* iterator) {
  StackFrame* caller_frame = iterator->NextFrame();
  ASSERT(caller_frame != NULL && caller_frame->IsDartFrame());
  const Function& caller = Function::Handle(caller_frame->LookupDartFunction());
  ASSERT(!caller.IsNull());
  return caller.script();
}


// Allocate a new instance of the given class name.
// TODO(hausner): Rename this NewCoreInstance to call out the fact that
// the class name is resolved in the core library implicitly?
RawInstance* Exceptions::NewInstance(const char* class_name) {
  const String& cls_name = String::Handle(Symbols::New(class_name));
  const Library& core_lib = Library::Handle(Library::CoreLibrary());
  Class& cls = Class::Handle(core_lib.LookupClass(cls_name));
  ASSERT(!cls.IsNull());
  // There are no parameterized error types, so no need to set type arguments.
  return Instance::New(cls);
}


// Assign the value to the field given by its name in the given instance.
void Exceptions::SetField(const Instance& instance,
                          const Class& cls,
                          const char* field_name,
                          const Object& value) {
  const Field& field = Field::Handle(cls.LookupInstanceField(
      String::Handle(Symbols::New(field_name))));
  ASSERT(!field.IsNull());
  instance.SetField(field, value);
}


// Initialize the fields 'url', 'line', and 'column' in the given instance
// according to the given token location in the given script.
void Exceptions::SetLocationFields(const Instance& instance,
                                   const Class& cls,
                                   const Script& script,
                                   intptr_t location) {
  SetField(instance, cls, "url", String::Handle(script.url()));
  intptr_t line, column;
  script.GetTokenLocation(location, &line, &column);
  SetField(instance, cls, "line", Smi::Handle(Smi::New(line)));
  SetField(instance, cls, "column", Smi::Handle(Smi::New(column)));
}


// Allocate, initialize, and throw a TypeError.
void Exceptions::CreateAndThrowTypeError(intptr_t location,
                                         const String& src_type_name,
                                         const String& dst_type_name,
                                         const String& dst_name,
                                         const String& malformed_error) {
  // Allocate a new instance of TypeError or CastError.
  Instance& type_error = Instance::Handle();
  Class& cls = Class::Handle();
  if (dst_name.Equals(kCastErrorDstName)) {
    type_error = NewInstance("CastErrorImplementation");
    cls = type_error.clazz();
    cls = cls.SuperClass();
  } else {
    type_error = NewInstance("TypeErrorImplementation");
    cls = type_error.clazz();
  }

  // Initialize 'url', 'line', and 'column' fields.
  DartFrameIterator iterator;
  const Script& script = Script::Handle(GetCallerScript(&iterator));
  // Location fields are defined in AssertionError, the superclass of TypeError.
  const Class& assertion_error_class = Class::Handle(cls.SuperClass());
  SetLocationFields(type_error, assertion_error_class, script, location);

  // Initialize field 'failedAssertion' in AssertionError superclass.
  // Printing the src_obj value would be possible, but ToString() is expensive
  // and not meaningful for all classes, so we just print '$expr instanceof...'.
  // Users should look at TypeError.ToString(), which contains more useful
  // information than AssertionError.failedAssertion.
  String& failed_assertion = String::Handle(String::New("$expr instanceof "));
  failed_assertion = String::Concat(failed_assertion, dst_type_name);
  SetField(type_error,
           assertion_error_class,
           "failedAssertion",
           failed_assertion);

  // Initialize field 'srcType'.
  SetField(type_error, cls, "srcType", src_type_name);

  // Initialize field 'dstType'.
  SetField(type_error, cls, "dstType", dst_type_name);

  // Initialize field 'dstName'.
  SetField(type_error, cls, "dstName", dst_name);

  // Initialize field 'malformedError'.
  SetField(type_error, cls, "malformedError", malformed_error);

  // Type errors in the core library may be difficult to diagnose.
  // Print type error information before throwing the error when debugging.
  if (FLAG_print_stacktrace_at_throw) {
    if (!malformed_error.IsNull()) {
      OS::Print("%s\n", malformed_error.ToCString());
    }
    intptr_t line, column;
    script.GetTokenLocation(location, &line, &column);
    OS::Print("'%s': Failed type check: line %"Pd" pos %"Pd": ",
              String::Handle(script.url()).ToCString(), line, column);
    if (!dst_name.IsNull() && (dst_name.Length() > 0)) {
      OS::Print("type '%s' is not a subtype of type '%s' of '%s'.\n",
                src_type_name.ToCString(),
                dst_type_name.ToCString(),
                dst_name.ToCString());
    } else {
      OS::Print("malformed type used.\n");
    }
  }
  // Throw TypeError instance.
  Exceptions::Throw(type_error);
  UNREACHABLE();
}


void Exceptions::Throw(const Instance& exception) {
  Isolate* isolate = Isolate::Current();
  isolate->debugger()->SignalExceptionThrown(exception);
  // Null object is a valid exception object.
  ThrowExceptionHelper(exception, Instance::Handle(isolate));
}


void Exceptions::ReThrow(const Instance& exception,
                         const Instance& stacktrace) {
  // Null object is a valid exception object.
  ThrowExceptionHelper(exception, stacktrace);
}


void Exceptions::PropagateError(const Error& error) {
  ASSERT(Isolate::Current()->top_exit_frame_info() != 0);
  if (error.IsUnhandledException()) {
    // If the error object represents an unhandled exception, then
    // rethrow the exception in the normal fashion.
    const UnhandledException& uhe = UnhandledException::Cast(error);
    const Instance& exc = Instance::Handle(uhe.exception());
    const Instance& stk = Instance::Handle(uhe.stacktrace());
    Exceptions::ReThrow(exc, stk);
  } else {
    // Return to the invocation stub and return this error object.  The
    // C++ code which invoked this dart sequence can check and do the
    // appropriate thing.
    uword handler_pc = 0;
    uword handler_sp = 0;
    uword handler_fp = 0;
    FindErrorHandler(&handler_pc, &handler_sp, &handler_fp);
    JumpToErrorHandler(handler_pc, handler_sp, handler_fp, error);
  }
  UNREACHABLE();
}


void Exceptions::ThrowByType(ExceptionType type, const Array& arguments) {
  const Object& result = Object::Handle(Create(type, arguments));
  if (result.IsError()) {
    // We got an error while constructing the exception object.
    // Propagate the error instead of throwing the exception.
    PropagateError(Error::Cast(result));
  } else {
    ASSERT(result.IsInstance());
    Throw(Instance::Cast(result));
  }
}


RawObject* Exceptions::Create(ExceptionType type, const Array& arguments) {
  Library& library = Library::Handle();
  const String* class_name = NULL;
  const String* constructor_name = &Symbols::Dot();
  switch (type) {
    case kNone:
      UNREACHABLE();
      break;
    case kRange:
      library = Library::CoreLibrary();
      class_name = &Symbols::RangeError();
      break;
    case kArgument:
      library = Library::CoreLibrary();
      class_name = &Symbols::ArgumentError();
      break;
    case kNoSuchMethod:
      library = Library::CoreLibrary();
      class_name = &Symbols::NoSuchMethodError();
      constructor_name = &String::Handle(Symbols::New("._withType"));
      break;
    case kFormat:
      library = Library::CoreLibrary();
      class_name = &Symbols::FormatException();
      break;
    case kUnsupported:
      library = Library::CoreLibrary();
      class_name = &Symbols::UnsupportedError();
      break;
    case kStackOverflow:
      library = Library::CoreLibrary();
      class_name = &Symbols::StackOverflowError();
      break;
    case kOutOfMemory:
      library = Library::CoreLibrary();
      class_name = &Symbols::OutOfMemoryError();
      break;
    case kInternalError:
      library = Library::CoreLibrary();
      class_name = &Symbols::InternalError();
      break;
    case kNullThrown:
      library = Library::CoreLibrary();
      class_name = &Symbols::NullThrownError();
      break;
    case kIsolateSpawn:
      library = Library::IsolateLibrary();
      class_name = &Symbols::IsolateSpawnException();
      break;
    case kIsolateUnhandledException:
      library = Library::IsolateLibrary();
      class_name = &Symbols::IsolateUnhandledException();
      break;
  }

  return DartLibraryCalls::ExceptionCreate(library,
                                           *class_name,
                                           *constructor_name,
                                           arguments);
}

}  // namespace dart