js/src/jsexn.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /*
   8  * JS standard exception implementation.
   9  */
  10
  11 #include "jsexn.h"
  12
  13 #include "mozilla/Assertions.h"
  14 #include "mozilla/Maybe.h"
  15 #include "mozilla/ScopeExit.h"
  16
  17 #include <new>
  18 #include <stdarg.h>
  19 #include <stdint.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <utility>
  23
  24 #include "jsapi.h"
  25 #include "jsfriendapi.h"
  26 #include "jstypes.h"
  27
  28 #include "frontend/FrontendContext.h"  // AutoReportFrontendContext
  29 #include "js/CharacterEncoding.h"      // JS::UTF8Chars, JS::ConstUTF8CharsZ
  30 #include "js/Class.h"
  31 #include "js/ColumnNumber.h"  // JS::ColumnNumberOneOrigin, JS::TaggedColumnNumberZeroOrigin
  32 #include "js/Conversions.h"
  33 #include "js/ErrorReport.h"             // JS::PrintError
  34 #include "js/Exception.h"               // JS::ExceptionStack
  35 #include "js/experimental/TypedData.h"  // JS_IsArrayBufferViewObject
  36 #include "js/friend/ErrorMessages.h"  // JSErrNum, js::GetErrorMessage, JSMSG_*
  37 #include "js/Object.h"                // JS::GetBuiltinClass
  38 #include "js/PropertyAndElement.h"    // JS_GetProperty, JS_HasProperty
  39 #include "js/SavedFrameAPI.h"
  40 #include "js/Stack.h"
  41 #include "js/UniquePtr.h"
  42 #include "js/Value.h"
  43 #include "js/Warnings.h"  // JS::{,Set}WarningReporter
  44 #include "js/Wrapper.h"
  45 #include "util/Memory.h"
  46 #include "util/StringBuffer.h"
  47 #include "vm/Compartment.h"
  48 #include "vm/ErrorObject.h"
  49 #include "vm/FrameIter.h"    // js::NonBuiltinFrameIter
  50 #include "vm/JSAtomUtils.h"  // ClassName
  51 #include "vm/JSContext.h"
  52 #include "vm/JSObject.h"
  53 #include "vm/JSScript.h"
  54 #include "vm/Realm.h"
  55 #include "vm/SavedFrame.h"
  56 #include "vm/SavedStacks.h"
  57 #include "vm/SelfHosting.h"
  58 #include "vm/Stack.h"
  59 #include "vm/StringType.h"
  60 #include "vm/SymbolType.h"
  61 #include "wasm/WasmJS.h"  // WasmExceptionObject
  62
  63 #include "vm/Compartment-inl.h"
  64 #include "vm/ErrorObject-inl.h"
  65 #include "vm/JSContext-inl.h"
  66 #include "vm/JSObject-inl.h"
  67 #include "vm/ObjectOperations-inl.h"  // js::GetProperty
  68 #include "vm/SavedStacks-inl.h"
  69
  70 using namespace js;
  71
  72 using JS::SavedFrameSelfHosted;
  73
  74 size_t ExtraMallocSize(JSErrorReport* report) {
  75   if (report->linebuf()) {
  76     /*
  77      * Count with null terminator and alignment.
  78      * See CopyExtraData for the details about alignment.
  79      */
  80     return (report->linebufLength() + 1) * sizeof(char16_t) + 1;
  81   }
  82
  83   return 0;
  84 }
  85
  86 size_t ExtraMallocSize(JSErrorNotes::Note* note) { return 0; }
  87
  88 bool CopyExtraData(JSContext* cx, uint8_t** cursor, JSErrorReport* copy,
  89                    JSErrorReport* report) {
  90   if (report->linebuf()) {
  91     /*
  92      * Make sure cursor is properly aligned for char16_t for platforms
  93      * which need it and it's at the end of the buffer on exit.
  94      */
  95     size_t alignment_backlog = 0;
  96     if (size_t(*cursor) % 2) {
  97       (*cursor)++;
  98     } else {
  99       alignment_backlog = 1;
 100     }
 101
 102     size_t linebufSize = (report->linebufLength() + 1) * sizeof(char16_t);
 103     const char16_t* linebufCopy = (const char16_t*)(*cursor);
 104     js_memcpy(*cursor, report->linebuf(), linebufSize);
 105     *cursor += linebufSize + alignment_backlog;
 106     copy->initBorrowedLinebuf(linebufCopy, report->linebufLength(),
 107                               report->tokenOffset());
 108   }
 109
 110   /* Copy non-pointer members. */
 111   copy->isMuted = report->isMuted;
 112   copy->exnType = report->exnType;
 113   copy->isWarning_ = report->isWarning_;
 114
 115   /* Deep copy notes. */
 116   if (report->notes) {
 117     auto copiedNotes = report->notes->copy(cx);
 118     if (!copiedNotes) {
 119       return false;
 120     }
 121     copy->notes = std::move(copiedNotes);
 122   } else {
 123     copy->notes.reset(nullptr);
 124   }
 125
 126   return true;
 127 }
 128
 129 bool CopyExtraData(JSContext* cx, uint8_t** cursor, JSErrorNotes::Note* copy,
 130                    JSErrorNotes::Note* report) {
 131   return true;
 132 }
 133
 134 template <typename T>
 135 static UniquePtr<T> CopyErrorHelper(JSContext* cx, T* report) {
 136   /*
 137    * We use a single malloc block to make a deep copy of JSErrorReport or
 138    * JSErrorNotes::Note, except JSErrorNotes linked from JSErrorReport with
 139    * the following layout:
 140    *   JSErrorReport or JSErrorNotes::Note
 141    *   char array with characters for message_
 142    *   char array with characters for filename
 143    *   char16_t array with characters for linebuf (only for JSErrorReport)
 144    * Such layout together with the properties enforced by the following
 145    * asserts does not need any extra alignment padding.
 146    */
 147   static_assert(sizeof(T) % sizeof(const char*) == 0);
 148   static_assert(sizeof(const char*) % sizeof(char16_t) == 0);
 149
 150   size_t filenameSize =
 151       report->filename ? strlen(report->filename.c_str()) + 1 : 0;
 152   size_t messageSize = 0;
 153   if (report->message()) {
 154     messageSize = strlen(report->message().c_str()) + 1;
 155   }
 156
 157   /*
 158    * The mallocSize can not overflow since it represents the sum of the
 159    * sizes of already allocated objects.
 160    */
 161   size_t mallocSize =
 162       sizeof(T) + messageSize + filenameSize + ExtraMallocSize(report);
 163   uint8_t* cursor = cx->pod_calloc<uint8_t>(mallocSize);
 164   if (!cursor) {
 165     return nullptr;
 166   }
 167
 168   UniquePtr<T> copy(new (cursor) T());
 169   cursor += sizeof(T);
 170
 171   if (report->message()) {
 172     copy->initBorrowedMessage((const char*)cursor);
 173     js_memcpy(cursor, report->message().c_str(), messageSize);
 174     cursor += messageSize;
 175   }
 176
 177   if (report->filename) {
 178     copy->filename = JS::ConstUTF8CharsZ((const char*)cursor);
 179     js_memcpy(cursor, report->filename.c_str(), filenameSize);
 180     cursor += filenameSize;
 181   }
 182
 183   if (!CopyExtraData(cx, &cursor, copy.get(), report)) {
 184     return nullptr;
 185   }
 186
 187   MOZ_ASSERT(cursor == (uint8_t*)copy.get() + mallocSize);
 188
 189   // errorMessageName should be static.
 190   copy->errorMessageName = report->errorMessageName;
 191
 192   /* Copy non-pointer members. */
 193   copy->sourceId = report->sourceId;
 194   copy->lineno = report->lineno;
 195   copy->column = report->column;
 196   copy->errorNumber = report->errorNumber;
 197
 198   return copy;
 199 }
 200
 201 UniquePtr<JSErrorNotes::Note> js::CopyErrorNote(JSContext* cx,
 202                                                 JSErrorNotes::Note* note) {
 203   return CopyErrorHelper(cx, note);
 204 }
 205
 206 UniquePtr<JSErrorReport> js::CopyErrorReport(JSContext* cx,
 207                                              JSErrorReport* report) {
 208   return CopyErrorHelper(cx, report);
 209 }
 210
 211 struct SuppressErrorsGuard {
 212   JSContext* cx;
 213   JS::WarningReporter prevReporter;
 214   JS::AutoSaveExceptionState prevState;
 215
 216   explicit SuppressErrorsGuard(JSContext* cx)
 217       : cx(cx),
 218         prevReporter(JS::SetWarningReporter(cx, nullptr)),
 219         prevState(cx) {}
 220
 221   ~SuppressErrorsGuard() { JS::SetWarningReporter(cx, prevReporter); }
 222 };
 223
 224 // Cut off the stack if it gets too deep (most commonly for infinite recursion
 225 // errors).
 226 static const size_t MAX_REPORTED_STACK_DEPTH = 1u << 7;
 227
 228 bool js::CaptureStack(JSContext* cx, MutableHandleObject stack) {
 229   return CaptureCurrentStack(
 230       cx, stack, JS::StackCapture(JS::MaxFrames(MAX_REPORTED_STACK_DEPTH)));
 231 }
 232
 233 JSString* js::ComputeStackString(JSContext* cx) {
 234   SuppressErrorsGuard seg(cx);
 235
 236   RootedObject stack(cx);
 237   if (!CaptureStack(cx, &stack)) {
 238     return nullptr;
 239   }
 240
 241   RootedString str(cx);
 242   if (!BuildStackString(cx, cx->realm()->principals(), stack, &str)) {
 243     return nullptr;
 244   }
 245
 246   return str.get();
 247 }
 248
 249 JSErrorReport* js::ErrorFromException(JSContext* cx, HandleObject objArg) {
 250   // It's ok to UncheckedUnwrap here, since all we do is get the
 251   // JSErrorReport, and consumers are careful with the information they get
 252   // from that anyway.  Anyone doing things that would expose anything in the
 253   // JSErrorReport to page script either does a security check on the
 254   // JSErrorReport's principal or also tries to do toString on our object and
 255   // will fail if they can't unwrap it.
 256   RootedObject obj(cx, UncheckedUnwrap(objArg));
 257   if (!obj->is<ErrorObject>()) {
 258     return nullptr;
 259   }
 260
 261   JSErrorReport* report = obj->as<ErrorObject>().getOrCreateErrorReport(cx);
 262   if (!report) {
 263     MOZ_ASSERT(cx->isThrowingOutOfMemory());
 264     cx->recoverFromOutOfMemory();
 265   }
 266
 267   return report;
 268 }
 269
 270 JS_PUBLIC_API JSObject* JS::ExceptionStackOrNull(HandleObject objArg) {
 271   ErrorObject* errorObject = objArg->maybeUnwrapIf<ErrorObject>();
 272   if (errorObject) {
 273     return errorObject->stack();
 274   }
 275
 276   WasmExceptionObject* wasmObject =
 277       objArg->maybeUnwrapIf<WasmExceptionObject>();
 278   if (wasmObject) {
 279     return wasmObject->stack();
 280   }
 281
 282   return nullptr;
 283 }
 284
 285 JS_PUBLIC_API JSLinearString* js::GetErrorTypeName(JSContext* cx,
 286                                                    int16_t exnType) {
 287   /*
 288    * JSEXN_INTERNALERR returns null to prevent that "InternalError: "
 289    * is prepended before "uncaught exception: "
 290    */
 291   if (exnType < 0 || exnType >= JSEXN_LIMIT || exnType == JSEXN_INTERNALERR ||
 292       exnType == JSEXN_WARN || exnType == JSEXN_NOTE) {
 293     return nullptr;
 294   }
 295   JSProtoKey key = GetExceptionProtoKey(JSExnType(exnType));
 296   return ClassName(key, cx);
 297 }
 298
 299 bool js::ErrorToException(JSContext* cx, JSErrorReport* reportp,
 300                           JSErrorCallback callback, void* userRef) {
 301   MOZ_ASSERT(!reportp->isWarning());
 302
 303   // Find the exception index associated with this error.
 304   JSErrNum errorNumber = static_cast<JSErrNum>(reportp->errorNumber);
 305   if (!callback) {
 306     callback = GetErrorMessage;
 307   }
 308   const JSErrorFormatString* errorString = callback(userRef, errorNumber);
 309   JSExnType exnType =
 310       errorString ? static_cast<JSExnType>(errorString->exnType) : JSEXN_ERR;
 311   MOZ_ASSERT(exnType < JSEXN_ERROR_LIMIT);
 312
 313   // Prevent infinite recursion.
 314   if (cx->generatingError) {
 315     return false;
 316   }
 317
 318   cx->generatingError = true;
 319   auto restore = mozilla::MakeScopeExit([cx] { cx->generatingError = false; });
 320
 321   // Create an exception object.
 322   RootedString messageStr(cx, reportp->newMessageString(cx));
 323   if (!messageStr) {
 324     return false;
 325   }
 326
 327   Rooted<JSString*> fileName(cx);
 328   if (const char* filename = reportp->filename.c_str()) {
 329     fileName =
 330         JS_NewStringCopyUTF8N(cx, JS::UTF8Chars(filename, strlen(filename)));
 331     if (!fileName) {
 332       return false;
 333     }
 334   } else {
 335     fileName = cx->emptyString();
 336   }
 337
 338   uint32_t sourceId = reportp->sourceId;
 339   uint32_t lineNumber = reportp->lineno;
 340   JS::ColumnNumberOneOrigin columnNumber = reportp->column;
 341
 342   // Error reports don't provide a |cause|, so we default to |Nothing| here.
 343   auto cause = JS::NothingHandleValue;
 344
 345   RootedObject stack(cx);
 346   if (!CaptureStack(cx, &stack)) {
 347     return false;
 348   }
 349
 350   UniquePtr<JSErrorReport> report = CopyErrorReport(cx, reportp);
 351   if (!report) {
 352     return false;
 353   }
 354
 355   ErrorObject* errObject =
 356       ErrorObject::create(cx, exnType, stack, fileName, sourceId, lineNumber,
 357                           columnNumber, std::move(report), messageStr, cause);
 358   if (!errObject) {
 359     return false;
 360   }
 361
 362   // Throw it.
 363   RootedValue errValue(cx, ObjectValue(*errObject));
 364   Rooted<SavedFrame*> nstack(cx);
 365   if (stack) {
 366     nstack = &stack->as<SavedFrame>();
 367   }
 368   cx->setPendingException(errValue, nstack);
 369   return true;
 370 }
 371
 372 using SniffingBehavior = JS::ErrorReportBuilder::SniffingBehavior;
 373
 374 static bool IsDuckTypedErrorObject(JSContext* cx, HandleObject exnObject,
 375                                    const char** filename_strp) {
 376   /*
 377    * This function is called from ErrorReport::init and so should not generate
 378    * any new exceptions.
 379    */
 380   AutoClearPendingException acpe(cx);
 381
 382   bool found;
 383   if (!JS_HasProperty(cx, exnObject, "message", &found) || !found) {
 384     return false;
 385   }
 386
 387   // First try "filename".
 388   const char* filename_str = *filename_strp;
 389   if (!JS_HasProperty(cx, exnObject, filename_str, &found)) {
 390     return false;
 391   }
 392   if (!found) {
 393     // If that doesn't work, try "fileName".
 394     filename_str = "fileName";
 395     if (!JS_HasProperty(cx, exnObject, filename_str, &found) || !found) {
 396       return false;
 397     }
 398   }
 399
 400   if (!JS_HasProperty(cx, exnObject, "lineNumber", &found) || !found) {
 401     return false;
 402   }
 403
 404   *filename_strp = filename_str;
 405   return true;
 406 }
 407
 408 static bool GetPropertyNoException(JSContext* cx, HandleObject obj,
 409                                    SniffingBehavior behavior,
 410                                    Handle<PropertyName*> name,
 411                                    MutableHandleValue vp) {
 412   // This function has no side-effects so always use it.
 413   if (GetPropertyPure(cx, obj, NameToId(name), vp.address())) {
 414     return true;
 415   }
 416
 417   if (behavior == SniffingBehavior::WithSideEffects) {
 418     AutoClearPendingException acpe(cx);
 419     return GetProperty(cx, obj, obj, name, vp);
 420   }
 421
 422   return false;
 423 }
 424
 425 // Create a new error message similar to what Error.prototype.toString would
 426 // produce when called on an object with those property values for name and
 427 // message.
 428 static JSString* FormatErrorMessage(JSContext* cx, HandleString name,
 429                                     HandleString message) {
 430   if (name && message) {
 431     AutoClearPendingException acpe(cx);
 432     JSStringBuilder sb(cx);
 433
 434     // Prefix the message with the error type, if it exists.
 435     if (!sb.append(name) || !sb.append(": ") || !sb.append(message)) {
 436       return nullptr;
 437     }
 438
 439     return sb.finishString();
 440   }
 441
 442   return name ? name : message;
 443 }
 444
 445 static JSString* ErrorReportToString(JSContext* cx, HandleObject exn,
 446                                      JSErrorReport* reportp,
 447                                      SniffingBehavior behavior) {
 448   // The error object might have custom `name` overwriting the exnType in the
 449   // error report. Try getting that property and use the exnType as a fallback.
 450   RootedString name(cx);
 451   RootedValue nameV(cx);
 452   if (GetPropertyNoException(cx, exn, behavior, cx->names().name, &nameV) &&
 453       nameV.isString()) {
 454     name = nameV.toString();
 455   }
 456
 457   // We do NOT want to use GetErrorTypeName() here because it will not do the
 458   // "right thing" for JSEXN_INTERNALERR.  That is, the caller of this API
 459   // expects that "InternalError: " will be prepended but GetErrorTypeName
 460   // goes out of its way to avoid this.
 461   if (!name) {
 462     JSExnType type = static_cast<JSExnType>(reportp->exnType);
 463     if (type != JSEXN_WARN && type != JSEXN_NOTE) {
 464       name = ClassName(GetExceptionProtoKey(type), cx);
 465     }
 466   }
 467
 468   RootedString message(cx);
 469   RootedValue messageV(cx);
 470   if (GetPropertyNoException(cx, exn, behavior, cx->names().message,
 471                              &messageV) &&
 472       messageV.isString()) {
 473     message = messageV.toString();
 474   }
 475
 476   if (!message) {
 477     message = reportp->newMessageString(cx);
 478     if (!message) {
 479       return nullptr;
 480     }
 481   }
 482
 483   return FormatErrorMessage(cx, name, message);
 484 }
 485
 486 JS::ErrorReportBuilder::ErrorReportBuilder(JSContext* cx)
 487     : reportp(nullptr), exnObject(cx) {}
 488
 489 JS::ErrorReportBuilder::~ErrorReportBuilder() = default;
 490
 491 bool JS::ErrorReportBuilder::init(JSContext* cx,
 492                                   const JS::ExceptionStack& exnStack,
 493                                   SniffingBehavior sniffingBehavior) {
 494   MOZ_ASSERT(!cx->isExceptionPending());
 495   MOZ_ASSERT(!reportp);
 496
 497   if (exnStack.exception().isObject()) {
 498     // Because ToString below could error and an exception object could become
 499     // unrooted, we must root our exception object, if any.
 500     exnObject = &exnStack.exception().toObject();
 501     reportp = ErrorFromException(cx, exnObject);
 502   }
 503
 504   // Be careful not to invoke ToString if we've already successfully extracted
 505   // an error report, since the exception might be wrapped in a security
 506   // wrapper, and ToString-ing it might throw.
 507   RootedString str(cx);
 508   if (reportp) {
 509     str = ErrorReportToString(cx, exnObject, reportp, sniffingBehavior);
 510   } else if (exnStack.exception().isSymbol()) {
 511     RootedValue strVal(cx);
 512     if (js::SymbolDescriptiveString(cx, exnStack.exception().toSymbol(),
 513                                     &strVal)) {
 514       str = strVal.toString();
 515     } else {
 516       str = nullptr;
 517     }
 518   } else if (exnObject && sniffingBehavior == NoSideEffects) {
 519     str = cx->names().Object;
 520   } else {
 521     str = js::ToString<CanGC>(cx, exnStack.exception());
 522   }
 523
 524   if (!str) {
 525     cx->clearPendingException();
 526   }
 527
 528   // If ErrorFromException didn't get us a JSErrorReport, then the object
 529   // was not an ErrorObject, security-wrapped or otherwise. However, it might
 530   // still quack like one. Give duck-typing a chance.  We start by looking for
 531   // "filename" (all lowercase), since that's where DOMExceptions store their
 532   // filename.  Then we check "fileName", which is where Errors store it.  We
 533   // have to do it in that order, because DOMExceptions have Error.prototype
 534   // on their proto chain, and hence also have a "fileName" property, but its
 535   // value is "".
 536   const char* filename_str = "filename";
 537   if (!reportp && exnObject && sniffingBehavior == WithSideEffects &&
 538       IsDuckTypedErrorObject(cx, exnObject, &filename_str)) {
 539     // Temporary value for pulling properties off of duck-typed objects.
 540     RootedValue val(cx);
 541
 542     RootedString name(cx);
 543     if (JS_GetProperty(cx, exnObject, "name", &val) && val.isString()) {
 544       name = val.toString();
 545     } else {
 546       cx->clearPendingException();
 547     }
 548
 549     RootedString msg(cx);
 550     if (JS_GetProperty(cx, exnObject, "message", &val) && val.isString()) {
 551       msg = val.toString();
 552     } else {
 553       cx->clearPendingException();
 554     }
 555
 556     // If we have the right fields, override the ToString we performed on
 557     // the exception object above with something built out of its quacks
 558     // (i.e. as much of |NameQuack: MessageQuack| as we can make).
 559     str = FormatErrorMessage(cx, name, msg);
 560
 561     {
 562       AutoClearPendingException acpe(cx);
 563       if (JS_GetProperty(cx, exnObject, filename_str, &val)) {
 564         RootedString tmp(cx, js::ToString<CanGC>(cx, val));
 565         if (tmp) {
 566           filename = JS_EncodeStringToUTF8(cx, tmp);
 567         }
 568       }
 569     }
 570     if (!filename) {
 571       filename = DuplicateString("");
 572       if (!filename) {
 573         ReportOutOfMemory(cx);
 574         return false;
 575       }
 576     }
 577
 578     uint32_t lineno;
 579     if (!JS_GetProperty(cx, exnObject, "lineNumber", &val) ||
 580         !ToUint32(cx, val, &lineno)) {
 581       cx->clearPendingException();
 582       lineno = 0;
 583     }
 584
 585     uint32_t column;
 586     if (!JS_GetProperty(cx, exnObject, "columnNumber", &val) ||
 587         !ToUint32(cx, val, &column)) {
 588       cx->clearPendingException();
 589       column = 0;
 590     }
 591
 592     reportp = &ownedReport;
 593     new (reportp) JSErrorReport();
 594     ownedReport.filename = JS::ConstUTF8CharsZ(filename.get());
 595     ownedReport.lineno = lineno;
 596     ownedReport.exnType = JSEXN_INTERNALERR;
 597     ownedReport.column = JS::ColumnNumberOneOrigin(column);
 598
 599     if (str) {
 600       // Note that using |str| for |message_| here is kind of wrong,
 601       // because |str| is supposed to be of the format
 602       // |ErrorName: ErrorMessage|, and |message_| is supposed to
 603       // correspond to |ErrorMessage|. But this is what we've
 604       // historically done for duck-typed error objects.
 605       //
 606       // If only this stuff could get specced one day...
 607       if (auto utf8 = JS_EncodeStringToUTF8(cx, str)) {
 608         ownedReport.initOwnedMessage(utf8.release());
 609       } else {
 610         cx->clearPendingException();
 611         str = nullptr;
 612       }
 613     }
 614   }
 615
 616   const char* utf8Message = nullptr;
 617   if (str) {
 618     toStringResultBytesStorage = JS_EncodeStringToUTF8(cx, str);
 619     utf8Message = toStringResultBytesStorage.get();
 620     if (!utf8Message) {
 621       cx->clearPendingException();
 622     }
 623   }
 624   if (!utf8Message) {
 625     utf8Message = "unknown (can't convert to string)";
 626   }
 627
 628   if (!reportp) {
 629     // This is basically an inlined version of
 630     //
 631     //   JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
 632     //                            JSMSG_UNCAUGHT_EXCEPTION, utf8Message);
 633     //
 634     // but without the reporting bits.  Instead it just puts all
 635     // the stuff we care about in our ownedReport and message_.
 636     if (!populateUncaughtExceptionReportUTF8(cx, exnStack.stack(),
 637                                              utf8Message)) {
 638       // Just give up.  We're out of memory or something; not much we can
 639       // do here.
 640       return false;
 641     }
 642   } else {
 643     toStringResult_ = JS::ConstUTF8CharsZ(utf8Message, strlen(utf8Message));
 644   }
 645
 646   return true;
 647 }
 648
 649 bool JS::ErrorReportBuilder::populateUncaughtExceptionReportUTF8(
 650     JSContext* cx, HandleObject stack, ...) {
 651   va_list ap;
 652   va_start(ap, stack);
 653   bool ok = populateUncaughtExceptionReportUTF8VA(cx, stack, ap);
 654   va_end(ap);
 655   return ok;
 656 }
 657
 658 bool JS::ErrorReportBuilder::populateUncaughtExceptionReportUTF8VA(
 659     JSContext* cx, HandleObject stack, va_list ap) {
 660   new (&ownedReport) JSErrorReport();
 661   ownedReport.isWarning_ = false;
 662   ownedReport.errorNumber = JSMSG_UNCAUGHT_EXCEPTION;
 663
 664   bool skippedAsync;
 665   Rooted<SavedFrame*> frame(
 666       cx, UnwrapSavedFrame(cx, cx->realm()->principals(), stack,
 667                            SavedFrameSelfHosted::Exclude, skippedAsync));
 668   if (frame) {
 669     filename = StringToNewUTF8CharsZ(cx, *frame->getSource());
 670     if (!filename) {
 671       return false;
 672     }
 673
 674     // |ownedReport.filename| inherits the lifetime of |ErrorReport::filename|.
 675     ownedReport.filename = JS::ConstUTF8CharsZ(filename.get());
 676     ownedReport.sourceId = frame->getSourceId();
 677     ownedReport.lineno = frame->getLine();
 678     ownedReport.column =
 679         JS::ColumnNumberOneOrigin(frame->getColumn().oneOriginValue());
 680     ownedReport.isMuted = frame->getMutedErrors();
 681   } else {
 682     // XXXbz this assumes the stack we have right now is still
 683     // related to our exception object.
 684     NonBuiltinFrameIter iter(cx, cx->realm()->principals());
 685     if (!iter.done()) {
 686       ownedReport.filename = JS::ConstUTF8CharsZ(iter.filename());
 687       JS::TaggedColumnNumberZeroOrigin column;
 688       ownedReport.sourceId =
 689           iter.hasScript() ? iter.script()->scriptSource()->id() : 0;
 690       ownedReport.lineno = iter.computeLine(&column);
 691       ownedReport.column = JS::ColumnNumberOneOrigin(column.oneOriginValue());
 692       ownedReport.isMuted = iter.mutedErrors();
 693     }
 694   }
 695
 696   AutoReportFrontendContext fc(cx);
 697   if (!ExpandErrorArgumentsVA(&fc, GetErrorMessage, nullptr,
 698                               JSMSG_UNCAUGHT_EXCEPTION, ArgumentsAreUTF8,
 699                               &ownedReport, ap)) {
 700     return false;
 701   }
 702
 703   toStringResult_ = ownedReport.message();
 704   reportp = &ownedReport;
 705   return true;
 706 }
 707
 708 JSObject* js::CopyErrorObject(JSContext* cx, Handle<ErrorObject*> err) {
 709   UniquePtr<JSErrorReport> copyReport;
 710   if (JSErrorReport* errorReport = err->getErrorReport()) {
 711     copyReport = CopyErrorReport(cx, errorReport);
 712     if (!copyReport) {
 713       return nullptr;
 714     }
 715   }
 716
 717   RootedString message(cx, err->getMessage());
 718   if (message && !cx->compartment()->wrap(cx, &message)) {
 719     return nullptr;
 720   }
 721   RootedString fileName(cx, err->fileName(cx));
 722   if (!cx->compartment()->wrap(cx, &fileName)) {
 723     return nullptr;
 724   }
 725   RootedObject stack(cx, err->stack());
 726   if (!cx->compartment()->wrap(cx, &stack)) {
 727     return nullptr;
 728   }
 729   if (stack && JS_IsDeadWrapper(stack)) {
 730     // ErrorObject::create expects |stack| to be either nullptr or a (possibly
 731     // wrapped) SavedFrame instance.
 732     stack = nullptr;
 733   }
 734   Rooted<mozilla::Maybe<Value>> cause(cx, mozilla::Nothing());
 735   if (auto maybeCause = err->getCause()) {
 736     RootedValue errorCause(cx, maybeCause.value());
 737     if (!cx->compartment()->wrap(cx, &errorCause)) {
 738       return nullptr;
 739     }
 740     cause = mozilla::Some(errorCause.get());
 741   }
 742   uint32_t sourceId = err->sourceId();
 743   uint32_t lineNumber = err->lineNumber();
 744   JS::ColumnNumberOneOrigin columnNumber = err->columnNumber();
 745   JSExnType errorType = err->type();
 746
 747   // Create the Error object.
 748   return ErrorObject::create(cx, errorType, stack, fileName, sourceId,
 749                              lineNumber, columnNumber, std::move(copyReport),
 750                              message, cause);
 751 }
 752
 753 JS_PUBLIC_API bool JS::CreateError(JSContext* cx, JSExnType type,
 754                                    HandleObject stack, HandleString fileName,
 755                                    uint32_t lineNumber,
 756                                    JS::ColumnNumberOneOrigin columnNumber,
 757                                    JSErrorReport* report, HandleString message,
 758                                    Handle<mozilla::Maybe<Value>> cause,
 759                                    MutableHandleValue rval) {
 760   cx->check(stack, fileName, message);
 761   AssertObjectIsSavedFrameOrWrapper(cx, stack);
 762
 763   js::UniquePtr<JSErrorReport> rep;
 764   if (report) {
 765     rep = CopyErrorReport(cx, report);
 766     if (!rep) {
 767       return false;
 768     }
 769   }
 770
 771   JSObject* obj =
 772       js::ErrorObject::create(cx, type, stack, fileName, 0, lineNumber,
 773                               columnNumber, std::move(rep), message, cause);
 774   if (!obj) {
 775     return false;
 776   }
 777
 778   rval.setObject(*obj);
 779   return true;
 780 }
 781
 782 const char* js::ValueToSourceForError(JSContext* cx, HandleValue val,
 783                                       UniqueChars& bytes) {
 784   if (val.isUndefined()) {
 785     return "undefined";
 786   }
 787
 788   if (val.isNull()) {
 789     return "null";
 790   }
 791
 792   AutoClearPendingException acpe(cx);
 793
 794   RootedString str(cx, JS_ValueToSource(cx, val));
 795   if (!str) {
 796     return "<<error converting value to string>>";
 797   }
 798
 799   JSStringBuilder sb(cx);
 800   if (val.hasObjectPayload()) {
 801     RootedObject valObj(cx, &val.getObjectPayload());
 802     ESClass cls;
 803     if (!JS::GetBuiltinClass(cx, valObj, &cls)) {
 804       return "<<error determining class of value>>";
 805     }
 806     const char* s;
 807     if (cls == ESClass::Array) {
 808       s = "the array ";
 809     } else if (cls == ESClass::ArrayBuffer) {
 810       s = "the array buffer ";
 811     } else if (JS_IsArrayBufferViewObject(valObj)) {
 812       s = "the typed array ";
 813 #ifdef ENABLE_RECORD_TUPLE
 814     } else if (cls == ESClass::Record) {
 815       s = "the record ";
 816     } else if (cls == ESClass::Tuple) {
 817       s = "the tuple ";
 818 #endif
 819     } else {
 820       s = "the object ";
 821     }
 822     if (!sb.append(s, strlen(s))) {
 823       return "<<error converting value to string>>";
 824     }
 825   } else if (val.isNumber()) {
 826     if (!sb.append("the number ")) {
 827       return "<<error converting value to string>>";
 828     }
 829   } else if (val.isString()) {
 830     if (!sb.append("the string ")) {
 831       return "<<error converting value to string>>";
 832     }
 833   } else if (val.isBigInt()) {
 834     if (!sb.append("the BigInt ")) {
 835       return "<<error converting value to string>>";
 836     }
 837   } else {
 838     MOZ_ASSERT(val.isBoolean() || val.isSymbol());
 839     bytes = StringToNewUTF8CharsZ(cx, *str);
 840     return bytes.get();
 841   }
 842   if (!sb.append(str)) {
 843     return "<<error converting value to string>>";
 844   }
 845   str = sb.finishString();
 846   if (!str) {
 847     return "<<error converting value to string>>";
 848   }
 849   bytes = StringToNewUTF8CharsZ(cx, *str);
 850   return bytes.get();
 851 }
 852
 853 bool js::GetInternalError(JSContext* cx, unsigned errorNumber,
 854                           MutableHandleValue error) {
 855   FixedInvokeArgs<1> args(cx);
 856   args[0].set(Int32Value(errorNumber));
 857   return CallSelfHostedFunction(cx, cx->names().GetInternalError,
 858                                 NullHandleValue, args, error);
 859 }
 860
 861 bool js::GetTypeError(JSContext* cx, unsigned errorNumber,
 862                       MutableHandleValue error) {
 863   FixedInvokeArgs<1> args(cx);
 864   args[0].set(Int32Value(errorNumber));
 865   return CallSelfHostedFunction(cx, cx->names().GetTypeError, NullHandleValue,
 866                                 args, error);
 867 }
 868
 869 bool js::GetAggregateError(JSContext* cx, unsigned errorNumber,
 870                            MutableHandleValue error) {
 871   FixedInvokeArgs<1> args(cx);
 872   args[0].set(Int32Value(errorNumber));
 873   return CallSelfHostedFunction(cx, cx->names().GetAggregateError,
 874                                 NullHandleValue, args, error);
 875 }
 876
 877 JS_PUBLIC_API mozilla::Maybe<Value> JS::GetExceptionCause(JSObject* exc) {
 878   if (!exc->is<ErrorObject>()) {
 879     return mozilla::Nothing();
 880   }
 881   auto& error = exc->as<ErrorObject>();
 882   return error.getCause();
 883 }