DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (5350524bb654)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * A set of structs for tracking exceptions that need to be thrown to JS:
 * ErrorResult and IgnoredErrorResult.
 *
 * Conceptually, these structs represent either success or an exception in the
 * process of being thrown.  This means that a failing ErrorResult _must_ be
 * handled in one of the following ways before coming off the stack:
 *
 * 1) Suppressed via SuppressException().
 * 2) Converted to a pure nsresult return value via StealNSResult().
 * 3) Converted to an actual pending exception on a JSContext via
 *    MaybeSetPendingException.
 * 4) Converted to an exception JS::Value (probably to then reject a Promise
 *    with) via dom::ToJSValue.
 *
 * An IgnoredErrorResult will automatically do the first of those four things.
 */

#ifndef mozilla_ErrorResult_h
#define mozilla_ErrorResult_h

#include <stdarg.h>

#include "js/GCAnnotations.h"
#include "js/Value.h"
#include "nscore.h"
#include "nsStringGlue.h"
#include "mozilla/Assertions.h"
#include "mozilla/Move.h"
#include "nsTArray.h"
#include "nsISupportsImpl.h"

namespace IPC {
class Message;
template <typename> struct ParamTraits;
} // namespace IPC
class PickleIterator;

namespace mozilla {

namespace dom {

enum ErrNum {
#define MSG_DEF(_name, _argc, _exn, _str) \
  _name,
#include "mozilla/dom/Errors.msg"
#undef MSG_DEF
  Err_Limit
};

// Debug-only compile-time table of the number of arguments of each error, for use in static_assert.
#if defined(DEBUG) && (defined(__clang__) || defined(__GNUC__))
uint16_t constexpr ErrorFormatNumArgs[] = {
#define MSG_DEF(_name, _argc, _exn, _str) \
  _argc,
#include "mozilla/dom/Errors.msg"
#undef MSG_DEF
};
#endif

uint16_t
GetErrorArgCount(const ErrNum aErrorNumber);

namespace binding_detail {
void ThrowErrorMessage(JSContext* aCx, const unsigned aErrorNumber, ...);
} // namespace binding_detail

template<typename... Ts>
inline bool
ThrowErrorMessage(JSContext* aCx, const ErrNum aErrorNumber, Ts&&... aArgs)
{
  binding_detail::ThrowErrorMessage(aCx, static_cast<const unsigned>(aErrorNumber),
                                    mozilla::Forward<Ts>(aArgs)...);
  return false;
}

struct StringArrayAppender
{
  static void Append(nsTArray<nsString>& aArgs, uint16_t aCount)
  {
    MOZ_RELEASE_ASSERT(aCount == 0, "Must give at least as many string arguments as are required by the ErrNum.");
  }

  template<typename... Ts>
  static void Append(nsTArray<nsString>& aArgs, uint16_t aCount, const nsAString& aFirst, Ts&&... aOtherArgs)
  {
    if (aCount == 0) {
      MOZ_ASSERT(false, "There should not be more string arguments provided than are required by the ErrNum.");
      return;
    }
    aArgs.AppendElement(aFirst);
    Append(aArgs, aCount - 1, Forward<Ts>(aOtherArgs)...);
  }
};

} // namespace dom

class ErrorResult;

namespace binding_danger {

/**
 * Templated implementation class for various ErrorResult-like things.  The
 * instantiations differ only in terms of their cleanup policies (used in the
 * destructor), which they can specify via the template argument.  Note that
 * this means it's safe to reinterpret_cast between the instantiations unless
 * you plan to invoke the destructor through such a cast pointer.
 *
 * A cleanup policy consists of two booleans: whether to assert that we've been
 * reported or suppressed, and whether to then go ahead and suppress the
 * exception.
 */
template<typename CleanupPolicy>
class TErrorResult {
public:
  TErrorResult()
    : mResult(NS_OK)
#ifdef DEBUG
    , mMightHaveUnreportedJSException(false)
    , mUnionState(HasNothing)
#endif
  {
  }

  ~TErrorResult() {
    AssertInOwningThread();

    if (CleanupPolicy::assertHandled) {
      // Consumers should have called one of MaybeSetPendingException
      // (possibly via ToJSValue), StealNSResult, and SuppressException
      AssertReportedOrSuppressed();
    }

    if (CleanupPolicy::suppress) {
      SuppressException();
    }

    // And now assert that we're in a good final state.
    AssertReportedOrSuppressed();
  }

  TErrorResult(TErrorResult&& aRHS)
    // Initialize mResult and whatever else we need to default-initialize, so
    // the ClearUnionData call in our operator= will do the right thing
    // (nothing).
    : TErrorResult()
  {
    *this = Move(aRHS);
  }
  TErrorResult& operator=(TErrorResult&& aRHS);

  explicit TErrorResult(nsresult aRv)
    : TErrorResult()
  {
    AssignErrorCode(aRv);
  }

  operator ErrorResult&();

  void Throw(nsresult rv) {
    MOZ_ASSERT(NS_FAILED(rv), "Please don't try throwing success");
    AssignErrorCode(rv);
  }

  // Duplicate our current state on the given TErrorResult object.  Any
  // existing errors or messages on the target will be suppressed before
  // cloning.  Our own error state remains unchanged.
  void CloneTo(TErrorResult& aRv) const;

  // Use SuppressException when you want to suppress any exception that might be
  // on the TErrorResult.  After this call, the TErrorResult will be back a "no
  // exception thrown" state.
  void SuppressException();

  // Use StealNSResult() when you want to safely convert the TErrorResult to
  // an nsresult that you will then return to a caller.  This will
  // SuppressException(), since there will no longer be a way to report it.
  nsresult StealNSResult() {
    nsresult rv = ErrorCode();
    SuppressException();
    // Don't propagate out our internal error codes that have special meaning.
    if (rv == NS_ERROR_TYPE_ERR ||
        rv == NS_ERROR_RANGE_ERR ||
        rv == NS_ERROR_DOM_JS_EXCEPTION ||
        rv == NS_ERROR_DOM_DOMEXCEPTION) {
      // What about NS_ERROR_DOM_EXCEPTION_ON_JSCONTEXT?  I guess that can be
      // legitimately passed on through....
      // What to pick here?
      return NS_ERROR_DOM_INVALID_STATE_ERR;
    }

    return rv;
  }

  // Use MaybeSetPendingException to convert a TErrorResult to a pending
  // exception on the given JSContext.  This is the normal "throw an exception"
  // codepath.
  //
  // The return value is false if the TErrorResult represents success, true
  // otherwise.  This does mean that in JSAPI method implementations you can't
  // just use this as |return rv.MaybeSetPendingException(cx)| (though you could
  // |return !rv.MaybeSetPendingException(cx)|), but in practice pretty much any
  // consumer would want to do some more work on the success codepath.  So
  // instead the way you use this is:
  //
  //   if (rv.MaybeSetPendingException(cx)) {
  //     bail out here
  //   }
  //   go on to do something useful
  //
  // The success path is inline, since it should be the common case and we don't
  // want to pay the price of a function call in some of the consumers of this
  // method in the common case.
  //
  // Note that a true return value does NOT mean there is now a pending
  // exception on aCx, due to uncatchable exceptions.  It should still be
  // considered equivalent to a JSAPI failure in terms of what callers should do
  // after true is returned.
  //
  // After this call, the TErrorResult will no longer return true from Failed(),
  // since the exception will have moved to the JSContext.
  bool MaybeSetPendingException(JSContext* cx)
  {
    WouldReportJSException();
    if (!Failed()) {
      return false;
    }

    SetPendingException(cx);
    return true;
  }

  // Use StealExceptionFromJSContext to convert a pending exception on a
  // JSContext to a TErrorResult.  This function must be called only when a
  // JSAPI operation failed.  It assumes that lack of pending exception on the
  // JSContext means an uncatchable exception was thrown.
  //
  // Codepaths that might call this method must call MightThrowJSException even
  // if the relevant JSAPI calls do not fail.
  //
  // When this function returns, JS_IsExceptionPending(cx) will definitely be
  // false.
  void StealExceptionFromJSContext(JSContext* cx);

  template<dom::ErrNum errorNumber, typename... Ts>
  void ThrowTypeError(Ts&&... messageArgs)
  {
    ThrowErrorWithMessage<errorNumber>(NS_ERROR_TYPE_ERR,
                                       Forward<Ts>(messageArgs)...);
  }

  template<dom::ErrNum errorNumber, typename... Ts>
  void ThrowRangeError(Ts&&... messageArgs)
  {
    ThrowErrorWithMessage<errorNumber>(NS_ERROR_RANGE_ERR,
                                       Forward<Ts>(messageArgs)...);
  }

  bool IsErrorWithMessage() const { return ErrorCode() == NS_ERROR_TYPE_ERR || ErrorCode() == NS_ERROR_RANGE_ERR; }

  // Facilities for throwing a preexisting JS exception value via this
  // TErrorResult.  The contract is that any code which might end up calling
  // ThrowJSException() or StealExceptionFromJSContext() must call
  // MightThrowJSException() even if no exception is being thrown.  Code that
  // conditionally calls ToJSValue on this TErrorResult only if Failed() must
  // first call WouldReportJSException even if this TErrorResult has not failed.
  //
  // The exn argument to ThrowJSException can be in any compartment.  It does
  // not have to be in the compartment of cx.  If someone later uses it, they
  // will wrap it into whatever compartment they're working in, as needed.
  void ThrowJSException(JSContext* cx, JS::Handle<JS::Value> exn);
  bool IsJSException() const { return ErrorCode() == NS_ERROR_DOM_JS_EXCEPTION; }

  // Facilities for throwing a DOMException.  If an empty message string is
  // passed to ThrowDOMException, the default message string for the given
  // nsresult will be used.  The passed-in string must be UTF-8.  The nsresult
  // passed in must be one we create DOMExceptions for; otherwise you may get an
  // XPConnect Exception.
  void ThrowDOMException(nsresult rv, const nsACString& message = EmptyCString());
  bool IsDOMException() const { return ErrorCode() == NS_ERROR_DOM_DOMEXCEPTION; }

  // Flag on the TErrorResult that whatever needs throwing has been
  // thrown on the JSContext already and we should not mess with it.
  // If nothing was thrown, this becomes an uncatchable exception.
  void NoteJSContextException(JSContext* aCx);

  // Check whether the TErrorResult says to just throw whatever is on
  // the JSContext already.
  bool IsJSContextException() {
    return ErrorCode() == NS_ERROR_DOM_EXCEPTION_ON_JSCONTEXT;
  }

  // Support for uncatchable exceptions.
  void ThrowUncatchableException() {
    Throw(NS_ERROR_UNCATCHABLE_EXCEPTION);
  }
  bool IsUncatchableException() const {
    return ErrorCode() == NS_ERROR_UNCATCHABLE_EXCEPTION;
  }

  void MOZ_ALWAYS_INLINE MightThrowJSException()
  {
#ifdef DEBUG
    mMightHaveUnreportedJSException = true;
#endif
  }
  void MOZ_ALWAYS_INLINE WouldReportJSException()
  {
#ifdef DEBUG
    mMightHaveUnreportedJSException = false;
#endif
  }

  // In the future, we can add overloads of Throw that take more
  // interesting things, like strings or DOM exception types or
  // something if desired.

  // Backwards-compat to make conversion simpler.  We don't call
  // Throw() here because people can easily pass success codes to
  // this.
  void operator=(nsresult rv) {
    AssignErrorCode(rv);
  }

  bool Failed() const {
    return NS_FAILED(mResult);
  }

  bool ErrorCodeIs(nsresult rv) const {
    return mResult == rv;
  }

  // For use in logging ONLY.
  uint32_t ErrorCodeAsInt() const {
    return static_cast<uint32_t>(ErrorCode());
  }

protected:
  nsresult ErrorCode() const {
    return mResult;
  }

private:
#ifdef DEBUG
  enum UnionState {
    HasMessage,
    HasDOMExceptionInfo,
    HasJSException,
    HasNothing
  };
#endif // DEBUG

  friend struct IPC::ParamTraits<TErrorResult>;
  friend struct IPC::ParamTraits<ErrorResult>;
  void SerializeMessage(IPC::Message* aMsg) const;
  bool DeserializeMessage(const IPC::Message* aMsg, PickleIterator* aIter);

  void SerializeDOMExceptionInfo(IPC::Message* aMsg) const;
  bool DeserializeDOMExceptionInfo(const IPC::Message* aMsg, PickleIterator* aIter);

  // Helper method that creates a new Message for this TErrorResult,
  // and returns the arguments array from that Message.
  nsTArray<nsString>& CreateErrorMessageHelper(const dom::ErrNum errorNumber, nsresult errorType);

  template<dom::ErrNum errorNumber, typename... Ts>
  void ThrowErrorWithMessage(nsresult errorType, Ts&&... messageArgs)
  {
#if defined(DEBUG) && (defined(__clang__) || defined(__GNUC__))
    static_assert(dom::ErrorFormatNumArgs[errorNumber] == sizeof...(messageArgs),
                  "Pass in the right number of arguments");
#endif

    ClearUnionData();

    nsTArray<nsString>& messageArgsArray = CreateErrorMessageHelper(errorNumber, errorType);
    uint16_t argCount = dom::GetErrorArgCount(errorNumber);
    dom::StringArrayAppender::Append(messageArgsArray, argCount,
                                     Forward<Ts>(messageArgs)...);
#ifdef DEBUG
    mUnionState = HasMessage;
#endif // DEBUG
  }

  MOZ_ALWAYS_INLINE void AssertInOwningThread() const {
#ifdef DEBUG
    NS_ASSERT_OWNINGTHREAD(TErrorResult);
#endif
  }

  void AssignErrorCode(nsresult aRv) {
    MOZ_ASSERT(aRv != NS_ERROR_TYPE_ERR, "Use ThrowTypeError()");
    MOZ_ASSERT(aRv != NS_ERROR_RANGE_ERR, "Use ThrowRangeError()");
    MOZ_ASSERT(!IsErrorWithMessage(), "Don't overwrite errors with message");
    MOZ_ASSERT(aRv != NS_ERROR_DOM_JS_EXCEPTION, "Use ThrowJSException()");
    MOZ_ASSERT(!IsJSException(), "Don't overwrite JS exceptions");
    MOZ_ASSERT(aRv != NS_ERROR_DOM_DOMEXCEPTION, "Use ThrowDOMException()");
    MOZ_ASSERT(!IsDOMException(), "Don't overwrite DOM exceptions");
    MOZ_ASSERT(aRv != NS_ERROR_XPC_NOT_ENOUGH_ARGS, "May need to bring back ThrowNotEnoughArgsError");
    MOZ_ASSERT(aRv != NS_ERROR_DOM_EXCEPTION_ON_JSCONTEXT,
               "Use NoteJSContextException");
    // Don't trust people anyway, though.
    if (aRv == NS_ERROR_TYPE_ERR ||
        aRv == NS_ERROR_RANGE_ERR ||
        aRv == NS_ERROR_DOM_JS_EXCEPTION ||
        aRv == NS_ERROR_DOM_DOMEXCEPTION) {
      mResult = NS_ERROR_UNEXPECTED;
    } else {
      mResult = aRv;
    }
  }

  void ClearMessage();
  void ClearDOMExceptionInfo();

  // ClearUnionData will try to clear the data in our
  // mMessage/mJSException/mDOMExceptionInfo union.  After this the union may be
  // in an uninitialized state (e.g. mMessage or mDOMExceptionInfo may be
  // pointing to deleted memory) and the caller must either reinitialize it or
  // change mResult to something that will not involve us touching the union
  // anymore.
  void ClearUnionData();

  // Implementation of MaybeSetPendingException for the case when we're a
  // failure result.
  void SetPendingException(JSContext* cx);

  // Methods for setting various specific kinds of pending exceptions.
  void SetPendingExceptionWithMessage(JSContext* cx);
  void SetPendingJSException(JSContext* cx);
  void SetPendingDOMException(JSContext* cx);
  void SetPendingGenericErrorException(JSContext* cx);

  MOZ_ALWAYS_INLINE void AssertReportedOrSuppressed()
  {
    MOZ_ASSERT(!Failed());
    MOZ_ASSERT(!mMightHaveUnreportedJSException);
    MOZ_ASSERT(mUnionState == HasNothing);
  }

  // Special values of mResult:
  // NS_ERROR_TYPE_ERR -- ThrowTypeError() called on us.
  // NS_ERROR_RANGE_ERR -- ThrowRangeError() called on us.
  // NS_ERROR_DOM_JS_EXCEPTION -- ThrowJSException() called on us.
  // NS_ERROR_UNCATCHABLE_EXCEPTION -- ThrowUncatchableException called on us.
  // NS_ERROR_DOM_DOMEXCEPTION -- ThrowDOMException() called on us.
  nsresult mResult;

  struct Message;
  struct DOMExceptionInfo;
  // mMessage is set by ThrowErrorWithMessage and reported (and deallocated) by
  // SetPendingExceptionWithMessage.
  // mJSException is set (and rooted) by ThrowJSException and reported
  // (and unrooted) by SetPendingJSException.
  // mDOMExceptionInfo is set by ThrowDOMException and reported
  // (and deallocated) by SetPendingDOMException.
  union {
    Message* mMessage; // valid when IsErrorWithMessage()
    JS::UninitializedValue mJSException; // valid when IsJSException()
    DOMExceptionInfo* mDOMExceptionInfo; // valid when IsDOMException()
  };

#ifdef DEBUG
  // Used to keep track of codepaths that might throw JS exceptions,
  // for assertion purposes.
  bool mMightHaveUnreportedJSException;

  // Used to keep track of what's stored in our union right now.  Note
  // that this may be set to HasNothing even if our mResult suggests
  // we should have something, if we have already cleaned up the
  // something.
  UnionState mUnionState;

  // The thread that created this TErrorResult
  NS_DECL_OWNINGTHREAD;
#endif

  // Not to be implemented, to make sure people always pass this by
  // reference, not by value.
  TErrorResult(const TErrorResult&) = delete;
  void operator=(const TErrorResult&) = delete;
};

struct JustAssertCleanupPolicy {
  static const bool assertHandled = true;
  static const bool suppress = false;
};

struct AssertAndSuppressCleanupPolicy {
  static const bool assertHandled = true;
  static const bool suppress = true;
};

struct JustSuppressCleanupPolicy {
  static const bool assertHandled = false;
  static const bool suppress = true;
};

} // namespace binding_danger

// A class people should normally use on the stack when they plan to actually
// do something with the exception.
class ErrorResult :
    public binding_danger::TErrorResult<binding_danger::AssertAndSuppressCleanupPolicy>
{
  typedef binding_danger::TErrorResult<binding_danger::AssertAndSuppressCleanupPolicy> BaseErrorResult;

public:
  ErrorResult()
    : BaseErrorResult()
  {}

  ErrorResult(ErrorResult&& aRHS)
    : BaseErrorResult(Move(aRHS))
  {}

  explicit ErrorResult(nsresult aRv)
    : BaseErrorResult(aRv)
  {}

  void operator=(nsresult rv)
  {
    BaseErrorResult::operator=(rv);
  }

  ErrorResult& operator=(ErrorResult&& aRHS)
  {
    BaseErrorResult::operator=(Move(aRHS));
    return *this;
  }

private:
  // Not to be implemented, to make sure people always pass this by
  // reference, not by value.
  ErrorResult(const ErrorResult&) = delete;
  void operator=(const ErrorResult&) = delete;
};

template<typename CleanupPolicy>
binding_danger::TErrorResult<CleanupPolicy>::operator ErrorResult&()
{
  return *static_cast<ErrorResult*>(
     reinterpret_cast<TErrorResult<AssertAndSuppressCleanupPolicy>*>(this));
}

// A class for use when an ErrorResult should just automatically be ignored.
// This doesn't inherit from ErrorResult so we don't make two separate calls to
// SuppressException.
class IgnoredErrorResult :
    public binding_danger::TErrorResult<binding_danger::JustSuppressCleanupPolicy>
{
};

/******************************************************************************
 ** Macros for checking results
 ******************************************************************************/

#define ENSURE_SUCCESS(res, ret)                                          \
  do {                                                                    \
    if (res.Failed()) {                                                   \
      nsCString msg;                                                      \
      msg.AppendPrintf("ENSURE_SUCCESS(%s, %s) failed with "              \
                       "result 0x%X", #res, #ret, res.ErrorCodeAsInt());  \
      NS_WARNING(msg.get());                                              \
      return ret;                                                         \
    }                                                                     \
  } while(0)

#define ENSURE_SUCCESS_VOID(res)                                          \
  do {                                                                    \
    if (res.Failed()) {                                                   \
      nsCString msg;                                                      \
      msg.AppendPrintf("ENSURE_SUCCESS_VOID(%s) failed with "             \
                       "result 0x%X", #res, res.ErrorCodeAsInt());        \
      NS_WARNING(msg.get());                                              \
      return;                                                             \
    }                                                                     \
  } while(0)

} // namespace mozilla

#endif /* mozilla_ErrorResult_h */