/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "common_throws.h"

#include <sstream>

#include "ScopedLocalRef.h"

#include "art_field-inl.h"
#include "art_method-inl.h"
#include "base/logging.h"
#include "class_linker-inl.h"
#include "dex_file-inl.h"
#include "dex_instruction-inl.h"
#include "invoke_type.h"
#include "mirror/class-inl.h"
#include "mirror/object-inl.h"
#include "mirror/object_array-inl.h"
#include "thread.h"
#include "verifier/method_verifier.h"

namespace art {

static void AddReferrerLocation(std::ostream& os, mirror::Class* referrer)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  if (referrer != nullptr) {
    std::string location(referrer->GetLocation());
    if (!location.empty()) {
      os << " (declaration of '" << PrettyDescriptor(referrer)
            << "' appears in " << location << ")";
    }
  }
}

static void ThrowException(const char* exception_descriptor,
                           mirror::Class* referrer, const char* fmt, va_list* args = nullptr)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  std::ostringstream msg;
  if (args != nullptr) {
    std::string vmsg;
    StringAppendV(&vmsg, fmt, *args);
    msg << vmsg;
  } else {
    msg << fmt;
  }
  AddReferrerLocation(msg, referrer);
  Thread* self = Thread::Current();
  self->ThrowNewException(exception_descriptor, msg.str().c_str());
}

static void ThrowWrappedException(const char* exception_descriptor,
                                  mirror::Class* referrer, const char* fmt, va_list* args = nullptr)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  std::ostringstream msg;
  if (args != nullptr) {
    std::string vmsg;
    StringAppendV(&vmsg, fmt, *args);
    msg << vmsg;
  } else {
    msg << fmt;
  }
  AddReferrerLocation(msg, referrer);
  Thread* self = Thread::Current();
  self->ThrowNewWrappedException(exception_descriptor, msg.str().c_str());
}

// AbstractMethodError

void ThrowAbstractMethodError(ArtMethod* method) {
  ThrowException("Ljava/lang/AbstractMethodError;", nullptr,
                 StringPrintf("abstract method \"%s\"",
                              PrettyMethod(method).c_str()).c_str());
}

void ThrowAbstractMethodError(uint32_t method_idx, const DexFile& dex_file) {
  ThrowException("Ljava/lang/AbstractMethodError;", /* referrer */ nullptr,
                 StringPrintf("abstract method \"%s\"",
                              PrettyMethod(method_idx,
                                           dex_file,
                                           /* with_signature */ true).c_str()).c_str());
}

// ArithmeticException

void ThrowArithmeticExceptionDivideByZero() {
  ThrowException("Ljava/lang/ArithmeticException;", nullptr, "divide by zero");
}

// ArrayIndexOutOfBoundsException

void ThrowArrayIndexOutOfBoundsException(int index, int length) {
  ThrowException("Ljava/lang/ArrayIndexOutOfBoundsException;", nullptr,
                 StringPrintf("length=%d; index=%d", length, index).c_str());
}

// ArrayStoreException

void ThrowArrayStoreException(mirror::Class* element_class, mirror::Class* array_class) {
  ThrowException("Ljava/lang/ArrayStoreException;", nullptr,
                 StringPrintf("%s cannot be stored in an array of type %s",
                              PrettyDescriptor(element_class).c_str(),
                              PrettyDescriptor(array_class).c_str()).c_str());
}

// ClassCastException

void ThrowClassCastException(mirror::Class* dest_type, mirror::Class* src_type) {
  ThrowException("Ljava/lang/ClassCastException;", nullptr,
                 StringPrintf("%s cannot be cast to %s",
                              PrettyDescriptor(src_type).c_str(),
                              PrettyDescriptor(dest_type).c_str()).c_str());
}

void ThrowClassCastException(const char* msg) {
  ThrowException("Ljava/lang/ClassCastException;", nullptr, msg);
}

// ClassCircularityError

void ThrowClassCircularityError(mirror::Class* c) {
  std::ostringstream msg;
  msg << PrettyDescriptor(c);
  ThrowException("Ljava/lang/ClassCircularityError;", c, msg.str().c_str());
}

void ThrowClassCircularityError(mirror::Class* c, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/ClassCircularityError;", c, fmt, &args);
  va_end(args);
}

// ClassFormatError

void ThrowClassFormatError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/ClassFormatError;", referrer, fmt, &args);
  va_end(args);
}

// IllegalAccessError

void ThrowIllegalAccessErrorClass(mirror::Class* referrer, mirror::Class* accessed) {
  std::ostringstream msg;
  msg << "Illegal class access: '" << PrettyDescriptor(referrer) << "' attempting to access '"
      << PrettyDescriptor(accessed) << "'";
  ThrowException("Ljava/lang/IllegalAccessError;", referrer, msg.str().c_str());
}

void ThrowIllegalAccessErrorClassForMethodDispatch(mirror::Class* referrer, mirror::Class* accessed,
                                                   ArtMethod* called,
                                                   InvokeType type) {
  std::ostringstream msg;
  msg << "Illegal class access ('" << PrettyDescriptor(referrer) << "' attempting to access '"
      << PrettyDescriptor(accessed) << "') in attempt to invoke " << type
      << " method " << PrettyMethod(called).c_str();
  ThrowException("Ljava/lang/IllegalAccessError;", referrer, msg.str().c_str());
}

void ThrowIllegalAccessErrorMethod(mirror::Class* referrer, ArtMethod* accessed) {
  std::ostringstream msg;
  msg << "Method '" << PrettyMethod(accessed) << "' is inaccessible to class '"
      << PrettyDescriptor(referrer) << "'";
  ThrowException("Ljava/lang/IllegalAccessError;", referrer, msg.str().c_str());
}

void ThrowIllegalAccessErrorField(mirror::Class* referrer, ArtField* accessed) {
  std::ostringstream msg;
  msg << "Field '" << PrettyField(accessed, false) << "' is inaccessible to class '"
      << PrettyDescriptor(referrer) << "'";
  ThrowException("Ljava/lang/IllegalAccessError;", referrer, msg.str().c_str());
}

void ThrowIllegalAccessErrorFinalField(ArtMethod* referrer, ArtField* accessed) {
  std::ostringstream msg;
  msg << "Final field '" << PrettyField(accessed, false) << "' cannot be written to by method '"
      << PrettyMethod(referrer) << "'";
  ThrowException("Ljava/lang/IllegalAccessError;",
                 referrer != nullptr ? referrer->GetDeclaringClass() : nullptr,
                 msg.str().c_str());
}

void ThrowIllegalAccessError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/IllegalAccessError;", referrer, fmt, &args);
  va_end(args);
}

// IllegalAccessException

void ThrowIllegalAccessException(const char* msg) {
  ThrowException("Ljava/lang/IllegalAccessException;", nullptr, msg);
}

// IllegalArgumentException

void ThrowIllegalArgumentException(const char* msg) {
  ThrowException("Ljava/lang/IllegalArgumentException;", nullptr, msg);
}


// IncompatibleClassChangeError

void ThrowIncompatibleClassChangeError(InvokeType expected_type, InvokeType found_type,
                                       ArtMethod* method, ArtMethod* referrer) {
  std::ostringstream msg;
  msg << "The method '" << PrettyMethod(method) << "' was expected to be of type "
      << expected_type << " but instead was found to be of type " << found_type;
  ThrowException("Ljava/lang/IncompatibleClassChangeError;",
                 referrer != nullptr ? referrer->GetDeclaringClass() : nullptr,
                 msg.str().c_str());
}

void ThrowIncompatibleClassChangeErrorClassForInterfaceSuper(ArtMethod* method,
                                                             mirror::Class* target_class,
                                                             mirror::Object* this_object,
                                                             ArtMethod* referrer) {
  // Referrer is calling interface_method on this_object, however, the interface_method isn't
  // implemented by this_object.
  CHECK(this_object != nullptr);
  std::ostringstream msg;
  msg << "Class '" << PrettyDescriptor(this_object->GetClass())
      << "' does not implement interface '" << PrettyDescriptor(target_class) << "' in call to '"
      << PrettyMethod(method) << "'";
  ThrowException("Ljava/lang/IncompatibleClassChangeError;",
                 referrer != nullptr ? referrer->GetDeclaringClass() : nullptr,
                 msg.str().c_str());
}

void ThrowIncompatibleClassChangeErrorClassForInterfaceDispatch(ArtMethod* interface_method,
                                                                mirror::Object* this_object,
                                                                ArtMethod* referrer) {
  // Referrer is calling interface_method on this_object, however, the interface_method isn't
  // implemented by this_object.
  CHECK(this_object != nullptr);
  std::ostringstream msg;
  msg << "Class '" << PrettyDescriptor(this_object->GetClass())
      << "' does not implement interface '"
      << PrettyDescriptor(interface_method->GetDeclaringClass())
      << "' in call to '" << PrettyMethod(interface_method) << "'";
  ThrowException("Ljava/lang/IncompatibleClassChangeError;",
                 referrer != nullptr ? referrer->GetDeclaringClass() : nullptr,
                 msg.str().c_str());
}

void ThrowIncompatibleClassChangeErrorField(ArtField* resolved_field, bool is_static,
                                            ArtMethod* referrer) {
  std::ostringstream msg;
  msg << "Expected '" << PrettyField(resolved_field) << "' to be a "
      << (is_static ? "static" : "instance") << " field" << " rather than a "
      << (is_static ? "instance" : "static") << " field";
  ThrowException("Ljava/lang/IncompatibleClassChangeError;", referrer->GetDeclaringClass(),
                 msg.str().c_str());
}

void ThrowIncompatibleClassChangeError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/IncompatibleClassChangeError;", referrer, fmt, &args);
  va_end(args);
}

void ThrowIncompatibleClassChangeErrorForMethodConflict(ArtMethod* method) {
  DCHECK(method != nullptr);
  ThrowException("Ljava/lang/IncompatibleClassChangeError;",
                 /*referrer*/nullptr,
                 StringPrintf("Conflicting default method implementations %s",
                              PrettyMethod(method).c_str()).c_str());
}


// IOException

void ThrowIOException(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/io/IOException;", nullptr, fmt, &args);
  va_end(args);
}

void ThrowWrappedIOException(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowWrappedException("Ljava/io/IOException;", nullptr, fmt, &args);
  va_end(args);
}

// LinkageError

void ThrowLinkageError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/LinkageError;", referrer, fmt, &args);
  va_end(args);
}

void ThrowWrappedLinkageError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowWrappedException("Ljava/lang/LinkageError;", referrer, fmt, &args);
  va_end(args);
}

// NegativeArraySizeException

void ThrowNegativeArraySizeException(int size) {
  ThrowException("Ljava/lang/NegativeArraySizeException;", nullptr,
                 StringPrintf("%d", size).c_str());
}

void ThrowNegativeArraySizeException(const char* msg) {
  ThrowException("Ljava/lang/NegativeArraySizeException;", nullptr, msg);
}

// NoSuchFieldError

void ThrowNoSuchFieldError(const StringPiece& scope, mirror::Class* c,
                           const StringPiece& type, const StringPiece& name) {
  std::ostringstream msg;
  std::string temp;
  msg << "No " << scope << "field " << name << " of type " << type
      << " in class " << c->GetDescriptor(&temp) << " or its superclasses";
  ThrowException("Ljava/lang/NoSuchFieldError;", c, msg.str().c_str());
}

void ThrowNoSuchFieldException(mirror::Class* c, const StringPiece& name) {
  std::ostringstream msg;
  std::string temp;
  msg << "No field " << name << " in class " << c->GetDescriptor(&temp);
  ThrowException("Ljava/lang/NoSuchFieldException;", c, msg.str().c_str());
}

// NoSuchMethodError

void ThrowNoSuchMethodError(InvokeType type, mirror::Class* c, const StringPiece& name,
                            const Signature& signature) {
  std::ostringstream msg;
  std::string temp;
  msg << "No " << type << " method " << name << signature
      << " in class " << c->GetDescriptor(&temp) << " or its super classes";
  ThrowException("Ljava/lang/NoSuchMethodError;", c, msg.str().c_str());
}

void ThrowNoSuchMethodError(uint32_t method_idx) {
  ArtMethod* method = Thread::Current()->GetCurrentMethod(nullptr);
  mirror::DexCache* dex_cache = method->GetDeclaringClass()->GetDexCache();
  const DexFile& dex_file = *dex_cache->GetDexFile();
  std::ostringstream msg;
  msg << "No method '" << PrettyMethod(method_idx, dex_file, true) << "'";
  ThrowException("Ljava/lang/NoSuchMethodError;",
                 method->GetDeclaringClass(), msg.str().c_str());
}

// NullPointerException

void ThrowNullPointerExceptionForFieldAccess(ArtField* field, bool is_read) {
  std::ostringstream msg;
  msg << "Attempt to " << (is_read ? "read from" : "write to")
      << " field '" << PrettyField(field, true) << "' on a null object reference";
  ThrowException("Ljava/lang/NullPointerException;", nullptr, msg.str().c_str());
}

static void ThrowNullPointerExceptionForMethodAccessImpl(uint32_t method_idx,
                                                         const DexFile& dex_file,
                                                         InvokeType type)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  std::ostringstream msg;
  msg << "Attempt to invoke " << type << " method '"
      << PrettyMethod(method_idx, dex_file, true) << "' on a null object reference";
  ThrowException("Ljava/lang/NullPointerException;", nullptr, msg.str().c_str());
}

void ThrowNullPointerExceptionForMethodAccess(uint32_t method_idx,
                                              InvokeType type) {
  mirror::DexCache* dex_cache =
      Thread::Current()->GetCurrentMethod(nullptr)->GetDeclaringClass()->GetDexCache();
  const DexFile& dex_file = *dex_cache->GetDexFile();
  ThrowNullPointerExceptionForMethodAccessImpl(method_idx, dex_file, type);
}

void ThrowNullPointerExceptionForMethodAccess(ArtMethod* method,
                                              InvokeType type) {
  mirror::DexCache* dex_cache = method->GetDeclaringClass()->GetDexCache();
  const DexFile& dex_file = *dex_cache->GetDexFile();
  ThrowNullPointerExceptionForMethodAccessImpl(method->GetDexMethodIndex(),
                                               dex_file, type);
}

static bool IsValidImplicitCheck(uintptr_t addr, ArtMethod* method, const Instruction& instr)
    SHARED_REQUIRES(Locks::mutator_lock_) {
  if (!CanDoImplicitNullCheckOn(addr)) {
    return false;
  }

  switch (instr.Opcode()) {
    case Instruction::INVOKE_DIRECT:
    case Instruction::INVOKE_DIRECT_RANGE:
    case Instruction::INVOKE_VIRTUAL:
    case Instruction::INVOKE_VIRTUAL_RANGE:
    case Instruction::INVOKE_INTERFACE:
    case Instruction::INVOKE_INTERFACE_RANGE:
    case Instruction::INVOKE_VIRTUAL_QUICK:
    case Instruction::INVOKE_VIRTUAL_RANGE_QUICK: {
      // Without inlining, we could just check that the offset is the class offset.
      // However, when inlining, the compiler can (validly) merge the null check with a field access
      // on the same object. Note that the stack map at the NPE will reflect the invoke's location,
      // which is the caller.
      return true;
    }

    case Instruction::IGET:
    case Instruction::IGET_WIDE:
    case Instruction::IGET_OBJECT:
    case Instruction::IGET_BOOLEAN:
    case Instruction::IGET_BYTE:
    case Instruction::IGET_CHAR:
    case Instruction::IGET_SHORT:
    case Instruction::IPUT:
    case Instruction::IPUT_WIDE:
    case Instruction::IPUT_OBJECT:
    case Instruction::IPUT_BOOLEAN:
    case Instruction::IPUT_BYTE:
    case Instruction::IPUT_CHAR:
    case Instruction::IPUT_SHORT: {
      ArtField* field =
          Runtime::Current()->GetClassLinker()->ResolveField(instr.VRegC_22c(), method, false);
      return (addr == 0) ||
          (addr == field->GetOffset().Uint32Value()) ||
          (kEmitCompilerReadBarrier && (addr == mirror::Object::MonitorOffset().Uint32Value()));
    }

    case Instruction::IGET_QUICK:
    case Instruction::IGET_BOOLEAN_QUICK:
    case Instruction::IGET_BYTE_QUICK:
    case Instruction::IGET_CHAR_QUICK:
    case Instruction::IGET_SHORT_QUICK:
    case Instruction::IGET_WIDE_QUICK:
    case Instruction::IGET_OBJECT_QUICK:
    case Instruction::IPUT_QUICK:
    case Instruction::IPUT_BOOLEAN_QUICK:
    case Instruction::IPUT_BYTE_QUICK:
    case Instruction::IPUT_CHAR_QUICK:
    case Instruction::IPUT_SHORT_QUICK:
    case Instruction::IPUT_WIDE_QUICK:
    case Instruction::IPUT_OBJECT_QUICK: {
      return (addr == 0u) ||
          (addr == instr.VRegC_22c()) ||
          (kEmitCompilerReadBarrier && (addr == mirror::Object::MonitorOffset().Uint32Value()));
    }

    case Instruction::AGET:
    case Instruction::AGET_WIDE:
    case Instruction::AGET_OBJECT:
    case Instruction::AGET_BOOLEAN:
    case Instruction::AGET_BYTE:
    case Instruction::AGET_CHAR:
    case Instruction::AGET_SHORT:
    case Instruction::APUT:
    case Instruction::APUT_WIDE:
    case Instruction::APUT_OBJECT:
    case Instruction::APUT_BOOLEAN:
    case Instruction::APUT_BYTE:
    case Instruction::APUT_CHAR:
    case Instruction::APUT_SHORT:
    case Instruction::FILL_ARRAY_DATA:
    case Instruction::ARRAY_LENGTH: {
      // The length access should crash. We currently do not do implicit checks on
      // the array access itself.
      return (addr == 0u) ||
          (addr == mirror::Array::LengthOffset().Uint32Value()) ||
          (kEmitCompilerReadBarrier && (addr == mirror::Object::MonitorOffset().Uint32Value()));
    }

    default: {
      // We have covered all the cases where an NPE could occur.
      // Note that this must be kept in sync with the compiler, and adding
      // any new way to do implicit checks in the compiler should also update
      // this code.
      return false;
    }
  }
}

void ThrowNullPointerExceptionFromDexPC(bool check_address, uintptr_t addr) {
  uint32_t throw_dex_pc;
  ArtMethod* method = Thread::Current()->GetCurrentMethod(&throw_dex_pc);
  const DexFile::CodeItem* code = method->GetCodeItem();
  CHECK_LT(throw_dex_pc, code->insns_size_in_code_units_);
  const Instruction* instr = Instruction::At(&code->insns_[throw_dex_pc]);
  if (check_address && !IsValidImplicitCheck(addr, method, *instr)) {
    const DexFile* dex_file = method->GetDeclaringClass()->GetDexCache()->GetDexFile();
    LOG(FATAL) << "Invalid address for an implicit NullPointerException check: "
               << "0x" << std::hex << addr << std::dec
               << ", at "
               << instr->DumpString(dex_file)
               << " in "
               << PrettyMethod(method);
  }

  switch (instr->Opcode()) {
    case Instruction::INVOKE_DIRECT:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_35c(), kDirect);
      break;
    case Instruction::INVOKE_DIRECT_RANGE:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_3rc(), kDirect);
      break;
    case Instruction::INVOKE_VIRTUAL:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_35c(), kVirtual);
      break;
    case Instruction::INVOKE_VIRTUAL_RANGE:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_3rc(), kVirtual);
      break;
    case Instruction::INVOKE_INTERFACE:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_35c(), kInterface);
      break;
    case Instruction::INVOKE_INTERFACE_RANGE:
      ThrowNullPointerExceptionForMethodAccess(instr->VRegB_3rc(), kInterface);
      break;
    case Instruction::INVOKE_VIRTUAL_QUICK:
    case Instruction::INVOKE_VIRTUAL_RANGE_QUICK: {
      // Since we replaced the method index, we ask the verifier to tell us which
      // method is invoked at this location.
      ArtMethod* invoked_method =
          verifier::MethodVerifier::FindInvokedMethodAtDexPc(method, throw_dex_pc);
      if (invoked_method != nullptr) {
        // NPE with precise message.
        ThrowNullPointerExceptionForMethodAccess(invoked_method, kVirtual);
      } else {
        // NPE with imprecise message.
        ThrowNullPointerException("Attempt to invoke a virtual method on a null object reference");
      }
      break;
    }
    case Instruction::IGET:
    case Instruction::IGET_WIDE:
    case Instruction::IGET_OBJECT:
    case Instruction::IGET_BOOLEAN:
    case Instruction::IGET_BYTE:
    case Instruction::IGET_CHAR:
    case Instruction::IGET_SHORT: {
      ArtField* field =
          Runtime::Current()->GetClassLinker()->ResolveField(instr->VRegC_22c(), method, false);
      ThrowNullPointerExceptionForFieldAccess(field, true /* read */);
      break;
    }
    case Instruction::IGET_QUICK:
    case Instruction::IGET_BOOLEAN_QUICK:
    case Instruction::IGET_BYTE_QUICK:
    case Instruction::IGET_CHAR_QUICK:
    case Instruction::IGET_SHORT_QUICK:
    case Instruction::IGET_WIDE_QUICK:
    case Instruction::IGET_OBJECT_QUICK: {
      // Since we replaced the field index, we ask the verifier to tell us which
      // field is accessed at this location.
      ArtField* field =
          verifier::MethodVerifier::FindAccessedFieldAtDexPc(method, throw_dex_pc);
      if (field != nullptr) {
        // NPE with precise message.
        ThrowNullPointerExceptionForFieldAccess(field, true /* read */);
      } else {
        // NPE with imprecise message.
        ThrowNullPointerException("Attempt to read from a field on a null object reference");
      }
      break;
    }
    case Instruction::IPUT:
    case Instruction::IPUT_WIDE:
    case Instruction::IPUT_OBJECT:
    case Instruction::IPUT_BOOLEAN:
    case Instruction::IPUT_BYTE:
    case Instruction::IPUT_CHAR:
    case Instruction::IPUT_SHORT: {
      ArtField* field =
          Runtime::Current()->GetClassLinker()->ResolveField(instr->VRegC_22c(), method, false);
      ThrowNullPointerExceptionForFieldAccess(field, false /* write */);
      break;
    }
    case Instruction::IPUT_QUICK:
    case Instruction::IPUT_BOOLEAN_QUICK:
    case Instruction::IPUT_BYTE_QUICK:
    case Instruction::IPUT_CHAR_QUICK:
    case Instruction::IPUT_SHORT_QUICK:
    case Instruction::IPUT_WIDE_QUICK:
    case Instruction::IPUT_OBJECT_QUICK: {
      // Since we replaced the field index, we ask the verifier to tell us which
      // field is accessed at this location.
      ArtField* field =
          verifier::MethodVerifier::FindAccessedFieldAtDexPc(method, throw_dex_pc);
      if (field != nullptr) {
        // NPE with precise message.
        ThrowNullPointerExceptionForFieldAccess(field, false /* write */);
      } else {
        // NPE with imprecise message.
        ThrowNullPointerException("Attempt to write to a field on a null object reference");
      }
      break;
    }
    case Instruction::AGET:
    case Instruction::AGET_WIDE:
    case Instruction::AGET_OBJECT:
    case Instruction::AGET_BOOLEAN:
    case Instruction::AGET_BYTE:
    case Instruction::AGET_CHAR:
    case Instruction::AGET_SHORT:
      ThrowException("Ljava/lang/NullPointerException;", nullptr,
                     "Attempt to read from null array");
      break;
    case Instruction::APUT:
    case Instruction::APUT_WIDE:
    case Instruction::APUT_OBJECT:
    case Instruction::APUT_BOOLEAN:
    case Instruction::APUT_BYTE:
    case Instruction::APUT_CHAR:
    case Instruction::APUT_SHORT:
      ThrowException("Ljava/lang/NullPointerException;", nullptr,
                     "Attempt to write to null array");
      break;
    case Instruction::ARRAY_LENGTH:
      ThrowException("Ljava/lang/NullPointerException;", nullptr,
                     "Attempt to get length of null array");
      break;
    case Instruction::FILL_ARRAY_DATA: {
      ThrowException("Ljava/lang/NullPointerException;", nullptr,
                     "Attempt to write to null array");
      break;
    }
    case Instruction::MONITOR_ENTER:
    case Instruction::MONITOR_EXIT: {
      ThrowException("Ljava/lang/NullPointerException;", nullptr,
                     "Attempt to do a synchronize operation on a null object");
      break;
    }
    default: {
      const DexFile* dex_file =
          method->GetDeclaringClass()->GetDexCache()->GetDexFile();
      LOG(FATAL) << "NullPointerException at an unexpected instruction: "
                 << instr->DumpString(dex_file)
                 << " in "
                 << PrettyMethod(method);
      break;
    }
  }
}

void ThrowNullPointerException(const char* msg) {
  ThrowException("Ljava/lang/NullPointerException;", nullptr, msg);
}

// RuntimeException

void ThrowRuntimeException(const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/RuntimeException;", nullptr, fmt, &args);
  va_end(args);
}

// Stack overflow.

void ThrowStackOverflowError(Thread* self) {
  if (self->IsHandlingStackOverflow()) {
    LOG(ERROR) << "Recursive stack overflow.";
    // We don't fail here because SetStackEndForStackOverflow will print better diagnostics.
  }

  self->SetStackEndForStackOverflow();  // Allow space on the stack for constructor to execute.
  JNIEnvExt* env = self->GetJniEnv();
  std::string msg("stack size ");
  msg += PrettySize(self->GetStackSize());

  // Avoid running Java code for exception initialization.
  // TODO: Checks to make this a bit less brittle.

  std::string error_msg;

  // Allocate an uninitialized object.
  ScopedLocalRef<jobject> exc(env,
                              env->AllocObject(WellKnownClasses::java_lang_StackOverflowError));
  if (exc.get() != nullptr) {
    // "Initialize".
    // StackOverflowError -> VirtualMachineError -> Error -> Throwable -> Object.
    // Only Throwable has "custom" fields:
    //   String detailMessage.
    //   Throwable cause (= this).
    //   List<Throwable> suppressedExceptions (= Collections.emptyList()).
    //   Object stackState;
    //   StackTraceElement[] stackTrace;
    // Only Throwable has a non-empty constructor:
    //   this.stackTrace = EmptyArray.STACK_TRACE_ELEMENT;
    //   fillInStackTrace();

    // detailMessage.
    // TODO: Use String::FromModifiedUTF...?
    ScopedLocalRef<jstring> s(env, env->NewStringUTF(msg.c_str()));
    if (s.get() != nullptr) {
      env->SetObjectField(exc.get(), WellKnownClasses::java_lang_Throwable_detailMessage, s.get());

      // cause.
      env->SetObjectField(exc.get(), WellKnownClasses::java_lang_Throwable_cause, exc.get());

      // suppressedExceptions.
      ScopedLocalRef<jobject> emptylist(env, env->GetStaticObjectField(
          WellKnownClasses::java_util_Collections,
          WellKnownClasses::java_util_Collections_EMPTY_LIST));
      CHECK(emptylist.get() != nullptr);
      env->SetObjectField(exc.get(),
                          WellKnownClasses::java_lang_Throwable_suppressedExceptions,
                          emptylist.get());

      // stackState is set as result of fillInStackTrace. fillInStackTrace calls
      // nativeFillInStackTrace.
      ScopedLocalRef<jobject> stack_state_val(env, nullptr);
      {
        ScopedObjectAccessUnchecked soa(env);
        stack_state_val.reset(soa.Self()->CreateInternalStackTrace<false>(soa));
      }
      if (stack_state_val.get() != nullptr) {
        env->SetObjectField(exc.get(),
                            WellKnownClasses::java_lang_Throwable_stackState,
                            stack_state_val.get());

        // stackTrace.
        ScopedLocalRef<jobject> stack_trace_elem(env, env->GetStaticObjectField(
            WellKnownClasses::libcore_util_EmptyArray,
            WellKnownClasses::libcore_util_EmptyArray_STACK_TRACE_ELEMENT));
        env->SetObjectField(exc.get(),
                            WellKnownClasses::java_lang_Throwable_stackTrace,
                            stack_trace_elem.get());
      } else {
        error_msg = "Could not create stack trace.";
      }
      // Throw the exception.
      self->SetException(reinterpret_cast<mirror::Throwable*>(self->DecodeJObject(exc.get())));
    } else {
      // Could not allocate a string object.
      error_msg = "Couldn't throw new StackOverflowError because JNI NewStringUTF failed.";
    }
  } else {
    error_msg = "Could not allocate StackOverflowError object.";
  }

  if (!error_msg.empty()) {
    LOG(WARNING) << error_msg;
    CHECK(self->IsExceptionPending());
  }

  bool explicit_overflow_check = Runtime::Current()->ExplicitStackOverflowChecks();
  self->ResetDefaultStackEnd();  // Return to default stack size.

  // And restore protection if implicit checks are on.
  if (!explicit_overflow_check) {
    self->ProtectStack();
  }
}

// StringIndexOutOfBoundsException

void ThrowStringIndexOutOfBoundsException(int index, int length) {
  ThrowException("Ljava/lang/StringIndexOutOfBoundsException;", nullptr,
                 StringPrintf("length=%d; index=%d", length, index).c_str());
}

// VerifyError

void ThrowVerifyError(mirror::Class* referrer, const char* fmt, ...) {
  va_list args;
  va_start(args, fmt);
  ThrowException("Ljava/lang/VerifyError;", referrer, fmt, &args);
  va_end(args);
}

}  // namespace art