Error.h revision 341825
1321369Sdim//===- llvm/Support/Error.h - Recoverable error handling --------*- C++ -*-===// 2303231Sdim// 3303231Sdim// The LLVM Compiler Infrastructure 4303231Sdim// 5303231Sdim// This file is distributed under the University of Illinois Open Source 6303231Sdim// License. See LICENSE.TXT for details. 7303231Sdim// 8303231Sdim//===----------------------------------------------------------------------===// 9303231Sdim// 10303231Sdim// This file defines an API used to report recoverable errors. 11303231Sdim// 12303231Sdim//===----------------------------------------------------------------------===// 13303231Sdim 14303231Sdim#ifndef LLVM_SUPPORT_ERROR_H 15303231Sdim#define LLVM_SUPPORT_ERROR_H 16303231Sdim 17314564Sdim#include "llvm/ADT/SmallVector.h" 18303231Sdim#include "llvm/ADT/STLExtras.h" 19303231Sdim#include "llvm/ADT/StringExtras.h" 20303231Sdim#include "llvm/ADT/Twine.h" 21314564Sdim#include "llvm/Config/abi-breaking.h" 22314564Sdim#include "llvm/Support/AlignOf.h" 23314564Sdim#include "llvm/Support/Compiler.h" 24303231Sdim#include "llvm/Support/Debug.h" 25321369Sdim#include "llvm/Support/ErrorHandling.h" 26303231Sdim#include "llvm/Support/ErrorOr.h" 27341825Sdim#include "llvm/Support/Format.h" 28303231Sdim#include "llvm/Support/raw_ostream.h" 29314564Sdim#include <algorithm> 30314564Sdim#include <cassert> 31314564Sdim#include <cstdint> 32314564Sdim#include <cstdlib> 33314564Sdim#include <functional> 34314564Sdim#include <memory> 35314564Sdim#include <new> 36314564Sdim#include <string> 37314564Sdim#include <system_error> 38314564Sdim#include <type_traits> 39314564Sdim#include <utility> 40303231Sdim#include <vector> 41303231Sdim 42303231Sdimnamespace llvm { 43303231Sdim 44314564Sdimclass ErrorSuccess; 45303231Sdim 46303231Sdim/// Base class for error info classes. Do not extend this directly: Extend 47303231Sdim/// the ErrorInfo template subclass instead. 48303231Sdimclass ErrorInfoBase { 49303231Sdimpublic: 50314564Sdim virtual ~ErrorInfoBase() = default; 51303231Sdim 52303231Sdim /// Print an error message to an output stream. 53303231Sdim virtual void log(raw_ostream &OS) const = 0; 54303231Sdim 55303231Sdim /// Return the error message as a string. 56303231Sdim virtual std::string message() const { 57303231Sdim std::string Msg; 58303231Sdim raw_string_ostream OS(Msg); 59303231Sdim log(OS); 60303231Sdim return OS.str(); 61303231Sdim } 62303231Sdim 63303231Sdim /// Convert this error to a std::error_code. 64303231Sdim /// 65303231Sdim /// This is a temporary crutch to enable interaction with code still 66303231Sdim /// using std::error_code. It will be removed in the future. 67303231Sdim virtual std::error_code convertToErrorCode() const = 0; 68303231Sdim 69321369Sdim // Returns the class ID for this type. 70321369Sdim static const void *classID() { return &ID; } 71321369Sdim 72321369Sdim // Returns the class ID for the dynamic type of this ErrorInfoBase instance. 73321369Sdim virtual const void *dynamicClassID() const = 0; 74321369Sdim 75303231Sdim // Check whether this instance is a subclass of the class identified by 76303231Sdim // ClassID. 77303231Sdim virtual bool isA(const void *const ClassID) const { 78303231Sdim return ClassID == classID(); 79303231Sdim } 80303231Sdim 81303231Sdim // Check whether this instance is a subclass of ErrorInfoT. 82303231Sdim template <typename ErrorInfoT> bool isA() const { 83303231Sdim return isA(ErrorInfoT::classID()); 84303231Sdim } 85303231Sdim 86303231Sdimprivate: 87303231Sdim virtual void anchor(); 88314564Sdim 89303231Sdim static char ID; 90303231Sdim}; 91303231Sdim 92303231Sdim/// Lightweight error class with error context and mandatory checking. 93303231Sdim/// 94303231Sdim/// Instances of this class wrap a ErrorInfoBase pointer. Failure states 95303231Sdim/// are represented by setting the pointer to a ErrorInfoBase subclass 96303231Sdim/// instance containing information describing the failure. Success is 97303231Sdim/// represented by a null pointer value. 98303231Sdim/// 99303231Sdim/// Instances of Error also contains a 'Checked' flag, which must be set 100303231Sdim/// before the destructor is called, otherwise the destructor will trigger a 101303231Sdim/// runtime error. This enforces at runtime the requirement that all Error 102303231Sdim/// instances be checked or returned to the caller. 103303231Sdim/// 104303231Sdim/// There are two ways to set the checked flag, depending on what state the 105303231Sdim/// Error instance is in. For Error instances indicating success, it 106303231Sdim/// is sufficient to invoke the boolean conversion operator. E.g.: 107303231Sdim/// 108314564Sdim/// @code{.cpp} 109303231Sdim/// Error foo(<...>); 110303231Sdim/// 111303231Sdim/// if (auto E = foo(<...>)) 112303231Sdim/// return E; // <- Return E if it is in the error state. 113303231Sdim/// // We have verified that E was in the success state. It can now be safely 114303231Sdim/// // destroyed. 115314564Sdim/// @endcode 116303231Sdim/// 117303231Sdim/// A success value *can not* be dropped. For example, just calling 'foo(<...>)' 118303231Sdim/// without testing the return value will raise a runtime error, even if foo 119303231Sdim/// returns success. 120303231Sdim/// 121303231Sdim/// For Error instances representing failure, you must use either the 122303231Sdim/// handleErrors or handleAllErrors function with a typed handler. E.g.: 123303231Sdim/// 124314564Sdim/// @code{.cpp} 125303231Sdim/// class MyErrorInfo : public ErrorInfo<MyErrorInfo> { 126303231Sdim/// // Custom error info. 127303231Sdim/// }; 128303231Sdim/// 129303231Sdim/// Error foo(<...>) { return make_error<MyErrorInfo>(...); } 130303231Sdim/// 131303231Sdim/// auto E = foo(<...>); // <- foo returns failure with MyErrorInfo. 132303231Sdim/// auto NewE = 133303231Sdim/// handleErrors(E, 134303231Sdim/// [](const MyErrorInfo &M) { 135303231Sdim/// // Deal with the error. 136303231Sdim/// }, 137303231Sdim/// [](std::unique_ptr<OtherError> M) -> Error { 138303231Sdim/// if (canHandle(*M)) { 139303231Sdim/// // handle error. 140303231Sdim/// return Error::success(); 141303231Sdim/// } 142303231Sdim/// // Couldn't handle this error instance. Pass it up the stack. 143303231Sdim/// return Error(std::move(M)); 144303231Sdim/// ); 145303231Sdim/// // Note - we must check or return NewE in case any of the handlers 146303231Sdim/// // returned a new error. 147314564Sdim/// @endcode 148303231Sdim/// 149303231Sdim/// The handleAllErrors function is identical to handleErrors, except 150303231Sdim/// that it has a void return type, and requires all errors to be handled and 151303231Sdim/// no new errors be returned. It prevents errors (assuming they can all be 152303231Sdim/// handled) from having to be bubbled all the way to the top-level. 153303231Sdim/// 154303231Sdim/// *All* Error instances must be checked before destruction, even if 155303231Sdim/// they're moved-assigned or constructed from Success values that have already 156303231Sdim/// been checked. This enforces checking through all levels of the call stack. 157314564Sdimclass LLVM_NODISCARD Error { 158303231Sdim // ErrorList needs to be able to yank ErrorInfoBase pointers out of this 159303231Sdim // class to add to the error list. 160303231Sdim friend class ErrorList; 161303231Sdim 162303231Sdim // handleErrors needs to be able to set the Checked flag. 163303231Sdim template <typename... HandlerTs> 164303231Sdim friend Error handleErrors(Error E, HandlerTs &&... Handlers); 165303231Sdim 166303231Sdim // Expected<T> needs to be able to steal the payload when constructed from an 167303231Sdim // error. 168314564Sdim template <typename T> friend class Expected; 169303231Sdim 170314564Sdimprotected: 171303231Sdim /// Create a success value. Prefer using 'Error::success()' for readability 172321369Sdim Error() { 173303231Sdim setPtr(nullptr); 174303231Sdim setChecked(false); 175303231Sdim } 176303231Sdim 177314564Sdimpublic: 178314564Sdim /// Create a success value. 179314564Sdim static ErrorSuccess success(); 180303231Sdim 181303231Sdim // Errors are not copy-constructable. 182303231Sdim Error(const Error &Other) = delete; 183303231Sdim 184303231Sdim /// Move-construct an error value. The newly constructed error is considered 185303231Sdim /// unchecked, even if the source error had been checked. The original error 186303231Sdim /// becomes a checked Success value, regardless of its original state. 187321369Sdim Error(Error &&Other) { 188303231Sdim setChecked(true); 189303231Sdim *this = std::move(Other); 190303231Sdim } 191303231Sdim 192303231Sdim /// Create an error value. Prefer using the 'make_error' function, but 193303231Sdim /// this constructor can be useful when "re-throwing" errors from handlers. 194303231Sdim Error(std::unique_ptr<ErrorInfoBase> Payload) { 195303231Sdim setPtr(Payload.release()); 196303231Sdim setChecked(false); 197303231Sdim } 198303231Sdim 199303231Sdim // Errors are not copy-assignable. 200303231Sdim Error &operator=(const Error &Other) = delete; 201303231Sdim 202303231Sdim /// Move-assign an error value. The current error must represent success, you 203303231Sdim /// you cannot overwrite an unhandled error. The current error is then 204303231Sdim /// considered unchecked. The source error becomes a checked success value, 205303231Sdim /// regardless of its original state. 206303231Sdim Error &operator=(Error &&Other) { 207303231Sdim // Don't allow overwriting of unchecked values. 208303231Sdim assertIsChecked(); 209303231Sdim setPtr(Other.getPtr()); 210303231Sdim 211303231Sdim // This Error is unchecked, even if the source error was checked. 212303231Sdim setChecked(false); 213303231Sdim 214303231Sdim // Null out Other's payload and set its checked bit. 215303231Sdim Other.setPtr(nullptr); 216303231Sdim Other.setChecked(true); 217303231Sdim 218303231Sdim return *this; 219303231Sdim } 220303231Sdim 221303231Sdim /// Destroy a Error. Fails with a call to abort() if the error is 222303231Sdim /// unchecked. 223303231Sdim ~Error() { 224303231Sdim assertIsChecked(); 225303231Sdim delete getPtr(); 226303231Sdim } 227303231Sdim 228303231Sdim /// Bool conversion. Returns true if this Error is in a failure state, 229303231Sdim /// and false if it is in an accept state. If the error is in a Success state 230303231Sdim /// it will be considered checked. 231303231Sdim explicit operator bool() { 232303231Sdim setChecked(getPtr() == nullptr); 233303231Sdim return getPtr() != nullptr; 234303231Sdim } 235303231Sdim 236303231Sdim /// Check whether one error is a subclass of another. 237303231Sdim template <typename ErrT> bool isA() const { 238303231Sdim return getPtr() && getPtr()->isA(ErrT::classID()); 239303231Sdim } 240303231Sdim 241321369Sdim /// Returns the dynamic class id of this error, or null if this is a success 242321369Sdim /// value. 243321369Sdim const void* dynamicClassID() const { 244321369Sdim if (!getPtr()) 245321369Sdim return nullptr; 246321369Sdim return getPtr()->dynamicClassID(); 247321369Sdim } 248321369Sdim 249303231Sdimprivate: 250327952Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 251327952Sdim // assertIsChecked() happens very frequently, but under normal circumstances 252327952Sdim // is supposed to be a no-op. So we want it to be inlined, but having a bunch 253327952Sdim // of debug prints can cause the function to be too large for inlining. So 254327952Sdim // it's important that we define this function out of line so that it can't be 255327952Sdim // inlined. 256327952Sdim LLVM_ATTRIBUTE_NORETURN 257327952Sdim void fatalUncheckedError() const; 258327952Sdim#endif 259327952Sdim 260303231Sdim void assertIsChecked() { 261314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 262327952Sdim if (LLVM_UNLIKELY(!getChecked() || getPtr())) 263327952Sdim fatalUncheckedError(); 264303231Sdim#endif 265303231Sdim } 266303231Sdim 267303231Sdim ErrorInfoBase *getPtr() const { 268314564Sdim return reinterpret_cast<ErrorInfoBase*>( 269314564Sdim reinterpret_cast<uintptr_t>(Payload) & 270314564Sdim ~static_cast<uintptr_t>(0x1)); 271303231Sdim } 272303231Sdim 273303231Sdim void setPtr(ErrorInfoBase *EI) { 274314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 275314564Sdim Payload = reinterpret_cast<ErrorInfoBase*>( 276314564Sdim (reinterpret_cast<uintptr_t>(EI) & 277314564Sdim ~static_cast<uintptr_t>(0x1)) | 278314564Sdim (reinterpret_cast<uintptr_t>(Payload) & 0x1)); 279303231Sdim#else 280303231Sdim Payload = EI; 281303231Sdim#endif 282303231Sdim } 283303231Sdim 284303231Sdim bool getChecked() const { 285314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 286314564Sdim return (reinterpret_cast<uintptr_t>(Payload) & 0x1) == 0; 287303231Sdim#else 288303231Sdim return true; 289303231Sdim#endif 290303231Sdim } 291303231Sdim 292303231Sdim void setChecked(bool V) { 293314564Sdim Payload = reinterpret_cast<ErrorInfoBase*>( 294314564Sdim (reinterpret_cast<uintptr_t>(Payload) & 295314564Sdim ~static_cast<uintptr_t>(0x1)) | 296314564Sdim (V ? 0 : 1)); 297303231Sdim } 298303231Sdim 299303231Sdim std::unique_ptr<ErrorInfoBase> takePayload() { 300303231Sdim std::unique_ptr<ErrorInfoBase> Tmp(getPtr()); 301303231Sdim setPtr(nullptr); 302303231Sdim setChecked(true); 303303231Sdim return Tmp; 304303231Sdim } 305303231Sdim 306341825Sdim friend raw_ostream &operator<<(raw_ostream &OS, const Error &E) { 307341825Sdim if (auto P = E.getPtr()) 308341825Sdim P->log(OS); 309341825Sdim else 310341825Sdim OS << "success"; 311341825Sdim return OS; 312341825Sdim } 313341825Sdim 314321369Sdim ErrorInfoBase *Payload = nullptr; 315303231Sdim}; 316303231Sdim 317314564Sdim/// Subclass of Error for the sole purpose of identifying the success path in 318314564Sdim/// the type system. This allows to catch invalid conversion to Expected<T> at 319314564Sdim/// compile time. 320314564Sdimclass ErrorSuccess : public Error {}; 321314564Sdim 322314564Sdiminline ErrorSuccess Error::success() { return ErrorSuccess(); } 323314564Sdim 324303231Sdim/// Make a Error instance representing failure using the given error info 325303231Sdim/// type. 326303231Sdimtemplate <typename ErrT, typename... ArgTs> Error make_error(ArgTs &&... Args) { 327303231Sdim return Error(llvm::make_unique<ErrT>(std::forward<ArgTs>(Args)...)); 328303231Sdim} 329303231Sdim 330303231Sdim/// Base class for user error types. Users should declare their error types 331303231Sdim/// like: 332303231Sdim/// 333303231Sdim/// class MyError : public ErrorInfo<MyError> { 334303231Sdim/// .... 335303231Sdim/// }; 336303231Sdim/// 337303231Sdim/// This class provides an implementation of the ErrorInfoBase::kind 338303231Sdim/// method, which is used by the Error RTTI system. 339303231Sdimtemplate <typename ThisErrT, typename ParentErrT = ErrorInfoBase> 340303231Sdimclass ErrorInfo : public ParentErrT { 341303231Sdimpublic: 342321369Sdim static const void *classID() { return &ThisErrT::ID; } 343321369Sdim 344321369Sdim const void *dynamicClassID() const override { return &ThisErrT::ID; } 345321369Sdim 346303231Sdim bool isA(const void *const ClassID) const override { 347303231Sdim return ClassID == classID() || ParentErrT::isA(ClassID); 348303231Sdim } 349303231Sdim}; 350303231Sdim 351303231Sdim/// Special ErrorInfo subclass representing a list of ErrorInfos. 352303231Sdim/// Instances of this class are constructed by joinError. 353303231Sdimclass ErrorList final : public ErrorInfo<ErrorList> { 354303231Sdim // handleErrors needs to be able to iterate the payload list of an 355303231Sdim // ErrorList. 356303231Sdim template <typename... HandlerTs> 357303231Sdim friend Error handleErrors(Error E, HandlerTs &&... Handlers); 358303231Sdim 359303231Sdim // joinErrors is implemented in terms of join. 360303231Sdim friend Error joinErrors(Error, Error); 361303231Sdim 362303231Sdimpublic: 363303231Sdim void log(raw_ostream &OS) const override { 364303231Sdim OS << "Multiple errors:\n"; 365303231Sdim for (auto &ErrPayload : Payloads) { 366303231Sdim ErrPayload->log(OS); 367303231Sdim OS << "\n"; 368303231Sdim } 369303231Sdim } 370303231Sdim 371303231Sdim std::error_code convertToErrorCode() const override; 372303231Sdim 373303231Sdim // Used by ErrorInfo::classID. 374303231Sdim static char ID; 375303231Sdim 376303231Sdimprivate: 377303231Sdim ErrorList(std::unique_ptr<ErrorInfoBase> Payload1, 378303231Sdim std::unique_ptr<ErrorInfoBase> Payload2) { 379303231Sdim assert(!Payload1->isA<ErrorList>() && !Payload2->isA<ErrorList>() && 380303231Sdim "ErrorList constructor payloads should be singleton errors"); 381303231Sdim Payloads.push_back(std::move(Payload1)); 382303231Sdim Payloads.push_back(std::move(Payload2)); 383303231Sdim } 384303231Sdim 385303231Sdim static Error join(Error E1, Error E2) { 386303231Sdim if (!E1) 387303231Sdim return E2; 388303231Sdim if (!E2) 389303231Sdim return E1; 390303231Sdim if (E1.isA<ErrorList>()) { 391303231Sdim auto &E1List = static_cast<ErrorList &>(*E1.getPtr()); 392303231Sdim if (E2.isA<ErrorList>()) { 393303231Sdim auto E2Payload = E2.takePayload(); 394303231Sdim auto &E2List = static_cast<ErrorList &>(*E2Payload); 395303231Sdim for (auto &Payload : E2List.Payloads) 396303231Sdim E1List.Payloads.push_back(std::move(Payload)); 397303231Sdim } else 398303231Sdim E1List.Payloads.push_back(E2.takePayload()); 399303231Sdim 400303231Sdim return E1; 401303231Sdim } 402303231Sdim if (E2.isA<ErrorList>()) { 403303231Sdim auto &E2List = static_cast<ErrorList &>(*E2.getPtr()); 404303231Sdim E2List.Payloads.insert(E2List.Payloads.begin(), E1.takePayload()); 405303231Sdim return E2; 406303231Sdim } 407303231Sdim return Error(std::unique_ptr<ErrorList>( 408303231Sdim new ErrorList(E1.takePayload(), E2.takePayload()))); 409303231Sdim } 410303231Sdim 411303231Sdim std::vector<std::unique_ptr<ErrorInfoBase>> Payloads; 412303231Sdim}; 413303231Sdim 414303231Sdim/// Concatenate errors. The resulting Error is unchecked, and contains the 415303231Sdim/// ErrorInfo(s), if any, contained in E1, followed by the 416303231Sdim/// ErrorInfo(s), if any, contained in E2. 417303231Sdiminline Error joinErrors(Error E1, Error E2) { 418303231Sdim return ErrorList::join(std::move(E1), std::move(E2)); 419303231Sdim} 420303231Sdim 421303231Sdim/// Tagged union holding either a T or a Error. 422303231Sdim/// 423303231Sdim/// This class parallels ErrorOr, but replaces error_code with Error. Since 424303231Sdim/// Error cannot be copied, this class replaces getError() with 425303231Sdim/// takeError(). It also adds an bool errorIsA<ErrT>() method for testing the 426303231Sdim/// error class type. 427314564Sdimtemplate <class T> class LLVM_NODISCARD Expected { 428321369Sdim template <class T1> friend class ExpectedAsOutParameter; 429303231Sdim template <class OtherT> friend class Expected; 430321369Sdim 431303231Sdim static const bool isRef = std::is_reference<T>::value; 432303231Sdim 433341825Sdim using wrap = std::reference_wrapper<typename std::remove_reference<T>::type>; 434303231Sdim 435321369Sdim using error_type = std::unique_ptr<ErrorInfoBase>; 436321369Sdim 437303231Sdimpublic: 438321369Sdim using storage_type = typename std::conditional<isRef, wrap, T>::type; 439321369Sdim using value_type = T; 440303231Sdim 441303231Sdimprivate: 442321369Sdim using reference = typename std::remove_reference<T>::type &; 443321369Sdim using const_reference = const typename std::remove_reference<T>::type &; 444321369Sdim using pointer = typename std::remove_reference<T>::type *; 445321369Sdim using const_pointer = const typename std::remove_reference<T>::type *; 446303231Sdim 447303231Sdimpublic: 448303231Sdim /// Create an Expected<T> error value from the given Error. 449303231Sdim Expected(Error Err) 450303231Sdim : HasError(true) 451314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 452314564Sdim // Expected is unchecked upon construction in Debug builds. 453314564Sdim , Unchecked(true) 454303231Sdim#endif 455303231Sdim { 456303231Sdim assert(Err && "Cannot create Expected<T> from Error success value."); 457314564Sdim new (getErrorStorage()) error_type(Err.takePayload()); 458303231Sdim } 459303231Sdim 460314564Sdim /// Forbid to convert from Error::success() implicitly, this avoids having 461314564Sdim /// Expected<T> foo() { return Error::success(); } which compiles otherwise 462314564Sdim /// but triggers the assertion above. 463314564Sdim Expected(ErrorSuccess) = delete; 464314564Sdim 465303231Sdim /// Create an Expected<T> success value from the given OtherT value, which 466303231Sdim /// must be convertible to T. 467303231Sdim template <typename OtherT> 468303231Sdim Expected(OtherT &&Val, 469303231Sdim typename std::enable_if<std::is_convertible<OtherT, T>::value>::type 470303231Sdim * = nullptr) 471303231Sdim : HasError(false) 472314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 473314564Sdim // Expected is unchecked upon construction in Debug builds. 474314564Sdim , Unchecked(true) 475303231Sdim#endif 476303231Sdim { 477303231Sdim new (getStorage()) storage_type(std::forward<OtherT>(Val)); 478303231Sdim } 479303231Sdim 480303231Sdim /// Move construct an Expected<T> value. 481303231Sdim Expected(Expected &&Other) { moveConstruct(std::move(Other)); } 482303231Sdim 483303231Sdim /// Move construct an Expected<T> value from an Expected<OtherT>, where OtherT 484303231Sdim /// must be convertible to T. 485303231Sdim template <class OtherT> 486303231Sdim Expected(Expected<OtherT> &&Other, 487303231Sdim typename std::enable_if<std::is_convertible<OtherT, T>::value>::type 488303231Sdim * = nullptr) { 489303231Sdim moveConstruct(std::move(Other)); 490303231Sdim } 491303231Sdim 492303231Sdim /// Move construct an Expected<T> value from an Expected<OtherT>, where OtherT 493303231Sdim /// isn't convertible to T. 494303231Sdim template <class OtherT> 495303231Sdim explicit Expected( 496303231Sdim Expected<OtherT> &&Other, 497303231Sdim typename std::enable_if<!std::is_convertible<OtherT, T>::value>::type * = 498303231Sdim nullptr) { 499303231Sdim moveConstruct(std::move(Other)); 500303231Sdim } 501303231Sdim 502303231Sdim /// Move-assign from another Expected<T>. 503303231Sdim Expected &operator=(Expected &&Other) { 504303231Sdim moveAssign(std::move(Other)); 505303231Sdim return *this; 506303231Sdim } 507303231Sdim 508303231Sdim /// Destroy an Expected<T>. 509303231Sdim ~Expected() { 510303231Sdim assertIsChecked(); 511303231Sdim if (!HasError) 512303231Sdim getStorage()->~storage_type(); 513303231Sdim else 514303231Sdim getErrorStorage()->~error_type(); 515303231Sdim } 516303231Sdim 517341825Sdim /// Return false if there is an error. 518303231Sdim explicit operator bool() { 519314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 520314564Sdim Unchecked = HasError; 521303231Sdim#endif 522303231Sdim return !HasError; 523303231Sdim } 524303231Sdim 525341825Sdim /// Returns a reference to the stored T value. 526303231Sdim reference get() { 527303231Sdim assertIsChecked(); 528303231Sdim return *getStorage(); 529303231Sdim } 530303231Sdim 531341825Sdim /// Returns a const reference to the stored T value. 532303231Sdim const_reference get() const { 533303231Sdim assertIsChecked(); 534303231Sdim return const_cast<Expected<T> *>(this)->get(); 535303231Sdim } 536303231Sdim 537341825Sdim /// Check that this Expected<T> is an error of type ErrT. 538303231Sdim template <typename ErrT> bool errorIsA() const { 539321369Sdim return HasError && (*getErrorStorage())->template isA<ErrT>(); 540303231Sdim } 541303231Sdim 542341825Sdim /// Take ownership of the stored error. 543303231Sdim /// After calling this the Expected<T> is in an indeterminate state that can 544303231Sdim /// only be safely destructed. No further calls (beside the destructor) should 545303231Sdim /// be made on the Expected<T> vaule. 546303231Sdim Error takeError() { 547314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 548314564Sdim Unchecked = false; 549303231Sdim#endif 550303231Sdim return HasError ? Error(std::move(*getErrorStorage())) : Error::success(); 551303231Sdim } 552303231Sdim 553341825Sdim /// Returns a pointer to the stored T value. 554303231Sdim pointer operator->() { 555303231Sdim assertIsChecked(); 556303231Sdim return toPointer(getStorage()); 557303231Sdim } 558303231Sdim 559341825Sdim /// Returns a const pointer to the stored T value. 560303231Sdim const_pointer operator->() const { 561303231Sdim assertIsChecked(); 562303231Sdim return toPointer(getStorage()); 563303231Sdim } 564303231Sdim 565341825Sdim /// Returns a reference to the stored T value. 566303231Sdim reference operator*() { 567303231Sdim assertIsChecked(); 568303231Sdim return *getStorage(); 569303231Sdim } 570303231Sdim 571341825Sdim /// Returns a const reference to the stored T value. 572303231Sdim const_reference operator*() const { 573303231Sdim assertIsChecked(); 574303231Sdim return *getStorage(); 575303231Sdim } 576303231Sdim 577303231Sdimprivate: 578303231Sdim template <class T1> 579303231Sdim static bool compareThisIfSameType(const T1 &a, const T1 &b) { 580303231Sdim return &a == &b; 581303231Sdim } 582303231Sdim 583303231Sdim template <class T1, class T2> 584303231Sdim static bool compareThisIfSameType(const T1 &a, const T2 &b) { 585303231Sdim return false; 586303231Sdim } 587303231Sdim 588303231Sdim template <class OtherT> void moveConstruct(Expected<OtherT> &&Other) { 589303231Sdim HasError = Other.HasError; 590314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 591314564Sdim Unchecked = true; 592314564Sdim Other.Unchecked = false; 593303231Sdim#endif 594303231Sdim 595303231Sdim if (!HasError) 596303231Sdim new (getStorage()) storage_type(std::move(*Other.getStorage())); 597303231Sdim else 598303231Sdim new (getErrorStorage()) error_type(std::move(*Other.getErrorStorage())); 599303231Sdim } 600303231Sdim 601303231Sdim template <class OtherT> void moveAssign(Expected<OtherT> &&Other) { 602303231Sdim assertIsChecked(); 603303231Sdim 604303231Sdim if (compareThisIfSameType(*this, Other)) 605303231Sdim return; 606303231Sdim 607303231Sdim this->~Expected(); 608303231Sdim new (this) Expected(std::move(Other)); 609303231Sdim } 610303231Sdim 611303231Sdim pointer toPointer(pointer Val) { return Val; } 612303231Sdim 613303231Sdim const_pointer toPointer(const_pointer Val) const { return Val; } 614303231Sdim 615303231Sdim pointer toPointer(wrap *Val) { return &Val->get(); } 616303231Sdim 617303231Sdim const_pointer toPointer(const wrap *Val) const { return &Val->get(); } 618303231Sdim 619303231Sdim storage_type *getStorage() { 620303231Sdim assert(!HasError && "Cannot get value when an error exists!"); 621303231Sdim return reinterpret_cast<storage_type *>(TStorage.buffer); 622303231Sdim } 623303231Sdim 624303231Sdim const storage_type *getStorage() const { 625303231Sdim assert(!HasError && "Cannot get value when an error exists!"); 626303231Sdim return reinterpret_cast<const storage_type *>(TStorage.buffer); 627303231Sdim } 628303231Sdim 629303231Sdim error_type *getErrorStorage() { 630303231Sdim assert(HasError && "Cannot get error when a value exists!"); 631303231Sdim return reinterpret_cast<error_type *>(ErrorStorage.buffer); 632303231Sdim } 633303231Sdim 634321369Sdim const error_type *getErrorStorage() const { 635321369Sdim assert(HasError && "Cannot get error when a value exists!"); 636321369Sdim return reinterpret_cast<const error_type *>(ErrorStorage.buffer); 637321369Sdim } 638321369Sdim 639321369Sdim // Used by ExpectedAsOutParameter to reset the checked flag. 640321369Sdim void setUnchecked() { 641321369Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 642321369Sdim Unchecked = true; 643321369Sdim#endif 644321369Sdim } 645321369Sdim 646327952Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 647327952Sdim LLVM_ATTRIBUTE_NORETURN 648327952Sdim LLVM_ATTRIBUTE_NOINLINE 649327952Sdim void fatalUncheckedExpected() const { 650327952Sdim dbgs() << "Expected<T> must be checked before access or destruction.\n"; 651327952Sdim if (HasError) { 652327952Sdim dbgs() << "Unchecked Expected<T> contained error:\n"; 653327952Sdim (*getErrorStorage())->log(dbgs()); 654327952Sdim } else 655327952Sdim dbgs() << "Expected<T> value was in success state. (Note: Expected<T> " 656327952Sdim "values in success mode must still be checked prior to being " 657327952Sdim "destroyed).\n"; 658327952Sdim abort(); 659327952Sdim } 660327952Sdim#endif 661327952Sdim 662303231Sdim void assertIsChecked() { 663314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 664327952Sdim if (LLVM_UNLIKELY(Unchecked)) 665327952Sdim fatalUncheckedExpected(); 666303231Sdim#endif 667303231Sdim } 668303231Sdim 669303231Sdim union { 670303231Sdim AlignedCharArrayUnion<storage_type> TStorage; 671303231Sdim AlignedCharArrayUnion<error_type> ErrorStorage; 672303231Sdim }; 673303231Sdim bool HasError : 1; 674314564Sdim#if LLVM_ENABLE_ABI_BREAKING_CHECKS 675314564Sdim bool Unchecked : 1; 676303231Sdim#endif 677303231Sdim}; 678303231Sdim 679327952Sdim/// Report a serious error, calling any installed error handler. See 680327952Sdim/// ErrorHandling.h. 681327952SdimLLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, 682327952Sdim bool gen_crash_diag = true); 683327952Sdim 684327952Sdim/// Report a fatal error if Err is a failure value. 685327952Sdim/// 686327952Sdim/// This function can be used to wrap calls to fallible functions ONLY when it 687327952Sdim/// is known that the Error will always be a success value. E.g. 688327952Sdim/// 689327952Sdim/// @code{.cpp} 690327952Sdim/// // foo only attempts the fallible operation if DoFallibleOperation is 691327952Sdim/// // true. If DoFallibleOperation is false then foo always returns 692327952Sdim/// // Error::success(). 693327952Sdim/// Error foo(bool DoFallibleOperation); 694327952Sdim/// 695327952Sdim/// cantFail(foo(false)); 696327952Sdim/// @endcode 697327952Sdiminline void cantFail(Error Err, const char *Msg = nullptr) { 698327952Sdim if (Err) { 699327952Sdim if (!Msg) 700327952Sdim Msg = "Failure value returned from cantFail wrapped call"; 701327952Sdim llvm_unreachable(Msg); 702327952Sdim } 703327952Sdim} 704327952Sdim 705327952Sdim/// Report a fatal error if ValOrErr is a failure value, otherwise unwraps and 706327952Sdim/// returns the contained value. 707327952Sdim/// 708327952Sdim/// This function can be used to wrap calls to fallible functions ONLY when it 709327952Sdim/// is known that the Error will always be a success value. E.g. 710327952Sdim/// 711327952Sdim/// @code{.cpp} 712327952Sdim/// // foo only attempts the fallible operation if DoFallibleOperation is 713327952Sdim/// // true. If DoFallibleOperation is false then foo always returns an int. 714327952Sdim/// Expected<int> foo(bool DoFallibleOperation); 715327952Sdim/// 716327952Sdim/// int X = cantFail(foo(false)); 717327952Sdim/// @endcode 718327952Sdimtemplate <typename T> 719327952SdimT cantFail(Expected<T> ValOrErr, const char *Msg = nullptr) { 720327952Sdim if (ValOrErr) 721327952Sdim return std::move(*ValOrErr); 722327952Sdim else { 723327952Sdim if (!Msg) 724327952Sdim Msg = "Failure value returned from cantFail wrapped call"; 725327952Sdim llvm_unreachable(Msg); 726327952Sdim } 727327952Sdim} 728327952Sdim 729327952Sdim/// Report a fatal error if ValOrErr is a failure value, otherwise unwraps and 730327952Sdim/// returns the contained reference. 731327952Sdim/// 732327952Sdim/// This function can be used to wrap calls to fallible functions ONLY when it 733327952Sdim/// is known that the Error will always be a success value. E.g. 734327952Sdim/// 735327952Sdim/// @code{.cpp} 736327952Sdim/// // foo only attempts the fallible operation if DoFallibleOperation is 737327952Sdim/// // true. If DoFallibleOperation is false then foo always returns a Bar&. 738327952Sdim/// Expected<Bar&> foo(bool DoFallibleOperation); 739327952Sdim/// 740327952Sdim/// Bar &X = cantFail(foo(false)); 741327952Sdim/// @endcode 742327952Sdimtemplate <typename T> 743327952SdimT& cantFail(Expected<T&> ValOrErr, const char *Msg = nullptr) { 744327952Sdim if (ValOrErr) 745327952Sdim return *ValOrErr; 746327952Sdim else { 747327952Sdim if (!Msg) 748327952Sdim Msg = "Failure value returned from cantFail wrapped call"; 749327952Sdim llvm_unreachable(Msg); 750327952Sdim } 751327952Sdim} 752327952Sdim 753327952Sdim/// Helper for testing applicability of, and applying, handlers for 754327952Sdim/// ErrorInfo types. 755327952Sdimtemplate <typename HandlerT> 756327952Sdimclass ErrorHandlerTraits 757327952Sdim : public ErrorHandlerTraits<decltype( 758327952Sdim &std::remove_reference<HandlerT>::type::operator())> {}; 759327952Sdim 760327952Sdim// Specialization functions of the form 'Error (const ErrT&)'. 761327952Sdimtemplate <typename ErrT> class ErrorHandlerTraits<Error (&)(ErrT &)> { 762327952Sdimpublic: 763327952Sdim static bool appliesTo(const ErrorInfoBase &E) { 764327952Sdim return E.template isA<ErrT>(); 765327952Sdim } 766327952Sdim 767327952Sdim template <typename HandlerT> 768327952Sdim static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) { 769327952Sdim assert(appliesTo(*E) && "Applying incorrect handler"); 770327952Sdim return H(static_cast<ErrT &>(*E)); 771327952Sdim } 772327952Sdim}; 773327952Sdim 774327952Sdim// Specialization functions of the form 'void (const ErrT&)'. 775327952Sdimtemplate <typename ErrT> class ErrorHandlerTraits<void (&)(ErrT &)> { 776327952Sdimpublic: 777327952Sdim static bool appliesTo(const ErrorInfoBase &E) { 778327952Sdim return E.template isA<ErrT>(); 779327952Sdim } 780327952Sdim 781327952Sdim template <typename HandlerT> 782327952Sdim static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) { 783327952Sdim assert(appliesTo(*E) && "Applying incorrect handler"); 784327952Sdim H(static_cast<ErrT &>(*E)); 785327952Sdim return Error::success(); 786327952Sdim } 787327952Sdim}; 788327952Sdim 789327952Sdim/// Specialization for functions of the form 'Error (std::unique_ptr<ErrT>)'. 790327952Sdimtemplate <typename ErrT> 791327952Sdimclass ErrorHandlerTraits<Error (&)(std::unique_ptr<ErrT>)> { 792327952Sdimpublic: 793327952Sdim static bool appliesTo(const ErrorInfoBase &E) { 794327952Sdim return E.template isA<ErrT>(); 795327952Sdim } 796327952Sdim 797327952Sdim template <typename HandlerT> 798327952Sdim static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) { 799327952Sdim assert(appliesTo(*E) && "Applying incorrect handler"); 800327952Sdim std::unique_ptr<ErrT> SubE(static_cast<ErrT *>(E.release())); 801327952Sdim return H(std::move(SubE)); 802327952Sdim } 803327952Sdim}; 804327952Sdim 805327952Sdim/// Specialization for functions of the form 'void (std::unique_ptr<ErrT>)'. 806327952Sdimtemplate <typename ErrT> 807327952Sdimclass ErrorHandlerTraits<void (&)(std::unique_ptr<ErrT>)> { 808327952Sdimpublic: 809327952Sdim static bool appliesTo(const ErrorInfoBase &E) { 810327952Sdim return E.template isA<ErrT>(); 811327952Sdim } 812327952Sdim 813327952Sdim template <typename HandlerT> 814327952Sdim static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) { 815327952Sdim assert(appliesTo(*E) && "Applying incorrect handler"); 816327952Sdim std::unique_ptr<ErrT> SubE(static_cast<ErrT *>(E.release())); 817327952Sdim H(std::move(SubE)); 818327952Sdim return Error::success(); 819327952Sdim } 820327952Sdim}; 821327952Sdim 822327952Sdim// Specialization for member functions of the form 'RetT (const ErrT&)'. 823327952Sdimtemplate <typename C, typename RetT, typename ErrT> 824327952Sdimclass ErrorHandlerTraits<RetT (C::*)(ErrT &)> 825327952Sdim : public ErrorHandlerTraits<RetT (&)(ErrT &)> {}; 826327952Sdim 827327952Sdim// Specialization for member functions of the form 'RetT (const ErrT&) const'. 828327952Sdimtemplate <typename C, typename RetT, typename ErrT> 829327952Sdimclass ErrorHandlerTraits<RetT (C::*)(ErrT &) const> 830327952Sdim : public ErrorHandlerTraits<RetT (&)(ErrT &)> {}; 831327952Sdim 832327952Sdim// Specialization for member functions of the form 'RetT (const ErrT&)'. 833327952Sdimtemplate <typename C, typename RetT, typename ErrT> 834327952Sdimclass ErrorHandlerTraits<RetT (C::*)(const ErrT &)> 835327952Sdim : public ErrorHandlerTraits<RetT (&)(ErrT &)> {}; 836327952Sdim 837327952Sdim// Specialization for member functions of the form 'RetT (const ErrT&) const'. 838327952Sdimtemplate <typename C, typename RetT, typename ErrT> 839327952Sdimclass ErrorHandlerTraits<RetT (C::*)(const ErrT &) const> 840327952Sdim : public ErrorHandlerTraits<RetT (&)(ErrT &)> {}; 841327952Sdim 842327952Sdim/// Specialization for member functions of the form 843327952Sdim/// 'RetT (std::unique_ptr<ErrT>)'. 844327952Sdimtemplate <typename C, typename RetT, typename ErrT> 845327952Sdimclass ErrorHandlerTraits<RetT (C::*)(std::unique_ptr<ErrT>)> 846327952Sdim : public ErrorHandlerTraits<RetT (&)(std::unique_ptr<ErrT>)> {}; 847327952Sdim 848327952Sdim/// Specialization for member functions of the form 849327952Sdim/// 'RetT (std::unique_ptr<ErrT>) const'. 850327952Sdimtemplate <typename C, typename RetT, typename ErrT> 851327952Sdimclass ErrorHandlerTraits<RetT (C::*)(std::unique_ptr<ErrT>) const> 852327952Sdim : public ErrorHandlerTraits<RetT (&)(std::unique_ptr<ErrT>)> {}; 853327952Sdim 854327952Sdiminline Error handleErrorImpl(std::unique_ptr<ErrorInfoBase> Payload) { 855327952Sdim return Error(std::move(Payload)); 856327952Sdim} 857327952Sdim 858327952Sdimtemplate <typename HandlerT, typename... HandlerTs> 859327952SdimError handleErrorImpl(std::unique_ptr<ErrorInfoBase> Payload, 860327952Sdim HandlerT &&Handler, HandlerTs &&... Handlers) { 861327952Sdim if (ErrorHandlerTraits<HandlerT>::appliesTo(*Payload)) 862327952Sdim return ErrorHandlerTraits<HandlerT>::apply(std::forward<HandlerT>(Handler), 863327952Sdim std::move(Payload)); 864327952Sdim return handleErrorImpl(std::move(Payload), 865327952Sdim std::forward<HandlerTs>(Handlers)...); 866327952Sdim} 867327952Sdim 868327952Sdim/// Pass the ErrorInfo(s) contained in E to their respective handlers. Any 869327952Sdim/// unhandled errors (or Errors returned by handlers) are re-concatenated and 870327952Sdim/// returned. 871327952Sdim/// Because this function returns an error, its result must also be checked 872327952Sdim/// or returned. If you intend to handle all errors use handleAllErrors 873327952Sdim/// (which returns void, and will abort() on unhandled errors) instead. 874327952Sdimtemplate <typename... HandlerTs> 875327952SdimError handleErrors(Error E, HandlerTs &&... Hs) { 876327952Sdim if (!E) 877327952Sdim return Error::success(); 878327952Sdim 879327952Sdim std::unique_ptr<ErrorInfoBase> Payload = E.takePayload(); 880327952Sdim 881327952Sdim if (Payload->isA<ErrorList>()) { 882327952Sdim ErrorList &List = static_cast<ErrorList &>(*Payload); 883327952Sdim Error R; 884327952Sdim for (auto &P : List.Payloads) 885327952Sdim R = ErrorList::join( 886327952Sdim std::move(R), 887327952Sdim handleErrorImpl(std::move(P), std::forward<HandlerTs>(Hs)...)); 888327952Sdim return R; 889327952Sdim } 890327952Sdim 891327952Sdim return handleErrorImpl(std::move(Payload), std::forward<HandlerTs>(Hs)...); 892327952Sdim} 893327952Sdim 894341825Sdim/// Behaves the same as handleErrors, except that by contract all errors 895341825Sdim/// *must* be handled by the given handlers (i.e. there must be no remaining 896341825Sdim/// errors after running the handlers, or llvm_unreachable is called). 897327952Sdimtemplate <typename... HandlerTs> 898327952Sdimvoid handleAllErrors(Error E, HandlerTs &&... Handlers) { 899327952Sdim cantFail(handleErrors(std::move(E), std::forward<HandlerTs>(Handlers)...)); 900327952Sdim} 901327952Sdim 902327952Sdim/// Check that E is a non-error, then drop it. 903341825Sdim/// If E is an error, llvm_unreachable will be called. 904327952Sdiminline void handleAllErrors(Error E) { 905327952Sdim cantFail(std::move(E)); 906327952Sdim} 907327952Sdim 908327952Sdim/// Handle any errors (if present) in an Expected<T>, then try a recovery path. 909327952Sdim/// 910327952Sdim/// If the incoming value is a success value it is returned unmodified. If it 911327952Sdim/// is a failure value then it the contained error is passed to handleErrors. 912327952Sdim/// If handleErrors is able to handle the error then the RecoveryPath functor 913327952Sdim/// is called to supply the final result. If handleErrors is not able to 914327952Sdim/// handle all errors then the unhandled errors are returned. 915327952Sdim/// 916327952Sdim/// This utility enables the follow pattern: 917327952Sdim/// 918327952Sdim/// @code{.cpp} 919327952Sdim/// enum FooStrategy { Aggressive, Conservative }; 920327952Sdim/// Expected<Foo> foo(FooStrategy S); 921327952Sdim/// 922327952Sdim/// auto ResultOrErr = 923327952Sdim/// handleExpected( 924327952Sdim/// foo(Aggressive), 925327952Sdim/// []() { return foo(Conservative); }, 926327952Sdim/// [](AggressiveStrategyError&) { 927327952Sdim/// // Implicitly conusme this - we'll recover by using a conservative 928327952Sdim/// // strategy. 929327952Sdim/// }); 930327952Sdim/// 931327952Sdim/// @endcode 932327952Sdimtemplate <typename T, typename RecoveryFtor, typename... HandlerTs> 933327952SdimExpected<T> handleExpected(Expected<T> ValOrErr, RecoveryFtor &&RecoveryPath, 934327952Sdim HandlerTs &&... Handlers) { 935327952Sdim if (ValOrErr) 936327952Sdim return ValOrErr; 937327952Sdim 938327952Sdim if (auto Err = handleErrors(ValOrErr.takeError(), 939327952Sdim std::forward<HandlerTs>(Handlers)...)) 940327952Sdim return std::move(Err); 941327952Sdim 942327952Sdim return RecoveryPath(); 943327952Sdim} 944327952Sdim 945327952Sdim/// Log all errors (if any) in E to OS. If there are any errors, ErrorBanner 946327952Sdim/// will be printed before the first one is logged. A newline will be printed 947327952Sdim/// after each error. 948327952Sdim/// 949327952Sdim/// This is useful in the base level of your program to allow clean termination 950327952Sdim/// (allowing clean deallocation of resources, etc.), while reporting error 951327952Sdim/// information to the user. 952327952Sdimvoid logAllUnhandledErrors(Error E, raw_ostream &OS, Twine ErrorBanner); 953327952Sdim 954327952Sdim/// Write all error messages (if any) in E to a string. The newline character 955327952Sdim/// is used to separate error messages. 956327952Sdiminline std::string toString(Error E) { 957327952Sdim SmallVector<std::string, 2> Errors; 958327952Sdim handleAllErrors(std::move(E), [&Errors](const ErrorInfoBase &EI) { 959327952Sdim Errors.push_back(EI.message()); 960327952Sdim }); 961327952Sdim return join(Errors.begin(), Errors.end(), "\n"); 962327952Sdim} 963327952Sdim 964327952Sdim/// Consume a Error without doing anything. This method should be used 965327952Sdim/// only where an error can be considered a reasonable and expected return 966327952Sdim/// value. 967327952Sdim/// 968327952Sdim/// Uses of this method are potentially indicative of design problems: If it's 969327952Sdim/// legitimate to do nothing while processing an "error", the error-producer 970327952Sdim/// might be more clearly refactored to return an Optional<T>. 971327952Sdiminline void consumeError(Error Err) { 972327952Sdim handleAllErrors(std::move(Err), [](const ErrorInfoBase &) {}); 973327952Sdim} 974327952Sdim 975341825Sdim/// Helper for converting an Error to a bool. 976341825Sdim/// 977341825Sdim/// This method returns true if Err is in an error state, or false if it is 978341825Sdim/// in a success state. Puts Err in a checked state in both cases (unlike 979341825Sdim/// Error::operator bool(), which only does this for success states). 980341825Sdiminline bool errorToBool(Error Err) { 981341825Sdim bool IsError = static_cast<bool>(Err); 982341825Sdim if (IsError) 983341825Sdim consumeError(std::move(Err)); 984341825Sdim return IsError; 985341825Sdim} 986341825Sdim 987327952Sdim/// Helper for Errors used as out-parameters. 988327952Sdim/// 989327952Sdim/// This helper is for use with the Error-as-out-parameter idiom, where an error 990327952Sdim/// is passed to a function or method by reference, rather than being returned. 991327952Sdim/// In such cases it is helpful to set the checked bit on entry to the function 992327952Sdim/// so that the error can be written to (unchecked Errors abort on assignment) 993327952Sdim/// and clear the checked bit on exit so that clients cannot accidentally forget 994327952Sdim/// to check the result. This helper performs these actions automatically using 995327952Sdim/// RAII: 996327952Sdim/// 997327952Sdim/// @code{.cpp} 998327952Sdim/// Result foo(Error &Err) { 999327952Sdim/// ErrorAsOutParameter ErrAsOutParam(&Err); // 'Checked' flag set 1000327952Sdim/// // <body of foo> 1001327952Sdim/// // <- 'Checked' flag auto-cleared when ErrAsOutParam is destructed. 1002327952Sdim/// } 1003327952Sdim/// @endcode 1004327952Sdim/// 1005327952Sdim/// ErrorAsOutParameter takes an Error* rather than Error& so that it can be 1006327952Sdim/// used with optional Errors (Error pointers that are allowed to be null). If 1007327952Sdim/// ErrorAsOutParameter took an Error reference, an instance would have to be 1008327952Sdim/// created inside every condition that verified that Error was non-null. By 1009327952Sdim/// taking an Error pointer we can just create one instance at the top of the 1010327952Sdim/// function. 1011327952Sdimclass ErrorAsOutParameter { 1012327952Sdimpublic: 1013327952Sdim ErrorAsOutParameter(Error *Err) : Err(Err) { 1014327952Sdim // Raise the checked bit if Err is success. 1015327952Sdim if (Err) 1016327952Sdim (void)!!*Err; 1017327952Sdim } 1018327952Sdim 1019327952Sdim ~ErrorAsOutParameter() { 1020327952Sdim // Clear the checked bit. 1021327952Sdim if (Err && !*Err) 1022327952Sdim *Err = Error::success(); 1023327952Sdim } 1024327952Sdim 1025327952Sdimprivate: 1026327952Sdim Error *Err; 1027327952Sdim}; 1028327952Sdim 1029321369Sdim/// Helper for Expected<T>s used as out-parameters. 1030321369Sdim/// 1031321369Sdim/// See ErrorAsOutParameter. 1032321369Sdimtemplate <typename T> 1033321369Sdimclass ExpectedAsOutParameter { 1034321369Sdimpublic: 1035321369Sdim ExpectedAsOutParameter(Expected<T> *ValOrErr) 1036321369Sdim : ValOrErr(ValOrErr) { 1037321369Sdim if (ValOrErr) 1038321369Sdim (void)!!*ValOrErr; 1039321369Sdim } 1040321369Sdim 1041321369Sdim ~ExpectedAsOutParameter() { 1042321369Sdim if (ValOrErr) 1043321369Sdim ValOrErr->setUnchecked(); 1044321369Sdim } 1045321369Sdim 1046321369Sdimprivate: 1047321369Sdim Expected<T> *ValOrErr; 1048321369Sdim}; 1049321369Sdim 1050303231Sdim/// This class wraps a std::error_code in a Error. 1051303231Sdim/// 1052303231Sdim/// This is useful if you're writing an interface that returns a Error 1053303231Sdim/// (or Expected) and you want to call code that still returns 1054303231Sdim/// std::error_codes. 1055303231Sdimclass ECError : public ErrorInfo<ECError> { 1056303231Sdim friend Error errorCodeToError(std::error_code); 1057314564Sdim 1058303231Sdimpublic: 1059303231Sdim void setErrorCode(std::error_code EC) { this->EC = EC; } 1060303231Sdim std::error_code convertToErrorCode() const override { return EC; } 1061303231Sdim void log(raw_ostream &OS) const override { OS << EC.message(); } 1062303231Sdim 1063303231Sdim // Used by ErrorInfo::classID. 1064303231Sdim static char ID; 1065303231Sdim 1066303231Sdimprotected: 1067303231Sdim ECError() = default; 1068303231Sdim ECError(std::error_code EC) : EC(EC) {} 1069314564Sdim 1070303231Sdim std::error_code EC; 1071303231Sdim}; 1072303231Sdim 1073303231Sdim/// The value returned by this function can be returned from convertToErrorCode 1074303231Sdim/// for Error values where no sensible translation to std::error_code exists. 1075303231Sdim/// It should only be used in this situation, and should never be used where a 1076303231Sdim/// sensible conversion to std::error_code is available, as attempts to convert 1077303231Sdim/// to/from this error will result in a fatal error. (i.e. it is a programmatic 1078303231Sdim///error to try to convert such a value). 1079303231Sdimstd::error_code inconvertibleErrorCode(); 1080303231Sdim 1081303231Sdim/// Helper for converting an std::error_code to a Error. 1082303231SdimError errorCodeToError(std::error_code EC); 1083303231Sdim 1084303231Sdim/// Helper for converting an ECError to a std::error_code. 1085303231Sdim/// 1086303231Sdim/// This method requires that Err be Error() or an ECError, otherwise it 1087303231Sdim/// will trigger a call to abort(). 1088303231Sdimstd::error_code errorToErrorCode(Error Err); 1089303231Sdim 1090303231Sdim/// Convert an ErrorOr<T> to an Expected<T>. 1091303231Sdimtemplate <typename T> Expected<T> errorOrToExpected(ErrorOr<T> &&EO) { 1092303231Sdim if (auto EC = EO.getError()) 1093303231Sdim return errorCodeToError(EC); 1094303231Sdim return std::move(*EO); 1095303231Sdim} 1096303231Sdim 1097303231Sdim/// Convert an Expected<T> to an ErrorOr<T>. 1098303231Sdimtemplate <typename T> ErrorOr<T> expectedToErrorOr(Expected<T> &&E) { 1099303231Sdim if (auto Err = E.takeError()) 1100303231Sdim return errorToErrorCode(std::move(Err)); 1101303231Sdim return std::move(*E); 1102303231Sdim} 1103303231Sdim 1104303231Sdim/// This class wraps a string in an Error. 1105303231Sdim/// 1106303231Sdim/// StringError is useful in cases where the client is not expected to be able 1107303231Sdim/// to consume the specific error message programmatically (for example, if the 1108303231Sdim/// error message is to be presented to the user). 1109303231Sdimclass StringError : public ErrorInfo<StringError> { 1110303231Sdimpublic: 1111303231Sdim static char ID; 1112314564Sdim 1113303231Sdim StringError(const Twine &S, std::error_code EC); 1114314564Sdim 1115303231Sdim void log(raw_ostream &OS) const override; 1116303231Sdim std::error_code convertToErrorCode() const override; 1117314564Sdim 1118321369Sdim const std::string &getMessage() const { return Msg; } 1119321369Sdim 1120303231Sdimprivate: 1121303231Sdim std::string Msg; 1122303231Sdim std::error_code EC; 1123303231Sdim}; 1124303231Sdim 1125341825Sdim/// Create formatted StringError object. 1126341825Sdimtemplate <typename... Ts> 1127341825SdimError createStringError(std::error_code EC, char const *Fmt, 1128341825Sdim const Ts &... Vals) { 1129341825Sdim std::string Buffer; 1130341825Sdim raw_string_ostream Stream(Buffer); 1131341825Sdim Stream << format(Fmt, Vals...); 1132341825Sdim return make_error<StringError>(Stream.str(), EC); 1133341825Sdim} 1134341825Sdim 1135341825SdimError createStringError(std::error_code EC, char const *Msg); 1136341825Sdim 1137303231Sdim/// Helper for check-and-exit error handling. 1138303231Sdim/// 1139303231Sdim/// For tool use only. NOT FOR USE IN LIBRARY CODE. 1140303231Sdim/// 1141303231Sdimclass ExitOnError { 1142303231Sdimpublic: 1143303231Sdim /// Create an error on exit helper. 1144303231Sdim ExitOnError(std::string Banner = "", int DefaultErrorExitCode = 1) 1145303231Sdim : Banner(std::move(Banner)), 1146303231Sdim GetExitCode([=](const Error &) { return DefaultErrorExitCode; }) {} 1147303231Sdim 1148303231Sdim /// Set the banner string for any errors caught by operator(). 1149303231Sdim void setBanner(std::string Banner) { this->Banner = std::move(Banner); } 1150303231Sdim 1151303231Sdim /// Set the exit-code mapper function. 1152303231Sdim void setExitCodeMapper(std::function<int(const Error &)> GetExitCode) { 1153303231Sdim this->GetExitCode = std::move(GetExitCode); 1154303231Sdim } 1155303231Sdim 1156303231Sdim /// Check Err. If it's in a failure state log the error(s) and exit. 1157303231Sdim void operator()(Error Err) const { checkError(std::move(Err)); } 1158303231Sdim 1159303231Sdim /// Check E. If it's in a success state then return the contained value. If 1160303231Sdim /// it's in a failure state log the error(s) and exit. 1161303231Sdim template <typename T> T operator()(Expected<T> &&E) const { 1162303231Sdim checkError(E.takeError()); 1163303231Sdim return std::move(*E); 1164303231Sdim } 1165303231Sdim 1166303231Sdim /// Check E. If it's in a success state then return the contained reference. If 1167303231Sdim /// it's in a failure state log the error(s) and exit. 1168303231Sdim template <typename T> T& operator()(Expected<T&> &&E) const { 1169303231Sdim checkError(E.takeError()); 1170303231Sdim return *E; 1171303231Sdim } 1172303231Sdim 1173303231Sdimprivate: 1174303231Sdim void checkError(Error Err) const { 1175303231Sdim if (Err) { 1176303231Sdim int ExitCode = GetExitCode(Err); 1177303231Sdim logAllUnhandledErrors(std::move(Err), errs(), Banner); 1178303231Sdim exit(ExitCode); 1179303231Sdim } 1180303231Sdim } 1181303231Sdim 1182303231Sdim std::string Banner; 1183303231Sdim std::function<int(const Error &)> GetExitCode; 1184303231Sdim}; 1185303231Sdim 1186314564Sdim} // end namespace llvm 1187303231Sdim 1188303231Sdim#endif // LLVM_SUPPORT_ERROR_H 1189