ErrorHandling.h

Go to the documentation of this file.

//===- llvm/Support/ErrorHandling.h - Fatal error handling ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines an API used to indicate fatal error conditions.  Non-fatal
// errors (most of them) should be handled through LLVMContext.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_SUPPORT_ERRORHANDLING_H
#define LLVM_SUPPORT_ERRORHANDLING_H
 
#include "llvm/Support/Compiler.h"
 
namespace llvm {
  class StringRef;
  class Twine;
 
  /// An error handler callback.
  typedef void (*fatal_error_handler_t)(void *user_data,
                                        const char *reason,
                                        bool gen_crash_diag);
 
  /// install_fatal_error_handler - Installs a new error handler to be used
  /// whenever a serious (non-recoverable) error is encountered by LLVM.
  ///
  /// If no error handler is installed the default is to print the error message
  /// to stderr, and call exit(1).  If an error handler is installed then it is
  /// the handler's responsibility to log the message, it will no longer be
  /// printed to stderr.  If the error handler returns, then exit(1) will be
  /// called.
  ///
  /// It is dangerous to naively use an error handler which throws an exception.
  /// Even though some applications desire to gracefully recover from arbitrary
  /// faults, blindly throwing exceptions through unfamiliar code isn't a way to
  /// achieve this.
  ///
  /// \param user_data - An argument which will be passed to the install error
  /// handler.
  void install_fatal_error_handler(fatal_error_handler_t handler,
                                   void *user_data = nullptr);
 
  /// Restores default error handling behaviour.
  void remove_fatal_error_handler();
 
  /// ScopedFatalErrorHandler - This is a simple helper class which just
  /// calls install_fatal_error_handler in its constructor and
  /// remove_fatal_error_handler in its destructor.
  struct ScopedFatalErrorHandler {
    explicit ScopedFatalErrorHandler(fatal_error_handler_t handler,
                                     void *user_data = nullptr) {
      install_fatal_error_handler(handler, user_data);
    }
 
    ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
  };
 
/// Reports a serious error, calling any installed error handler. These
/// functions are intended to be used for error conditions which are outside
/// the control of the compiler (I/O errors, invalid user input, etc.)
///
/// If no error handler is installed the default is to print the message to
/// standard error, followed by a newline.
/// After the error handler is called this function will call abort(), it
/// does not return.
/// NOTE: The std::string variant was removed to avoid a <string> dependency.
[[noreturn]] void report_fatal_error(const char *reason,
                                     bool gen_crash_diag = true);
[[noreturn]] void report_fatal_error(StringRef reason,
                                     bool gen_crash_diag = true);
[[noreturn]] void report_fatal_error(const Twine &reason,
                                     bool gen_crash_diag = true);
 
/// Installs a new bad alloc error handler that should be used whenever a
/// bad alloc error, e.g. failing malloc/calloc, is encountered by LLVM.
///
/// The user can install a bad alloc handler, in order to define the behavior
/// in case of failing allocations, e.g. throwing an exception. Note that this
/// handler must not trigger any additional allocations itself.
///
/// If no error handler is installed the default is to print the error message
/// to stderr, and call exit(1).  If an error handler is installed then it is
/// the handler's responsibility to log the message, it will no longer be
/// printed to stderr.  If the error handler returns, then exit(1) will be
/// called.
///
///
/// \param user_data - An argument which will be passed to the installed error
/// handler.
void install_bad_alloc_error_handler(fatal_error_handler_t handler,
                                     void *user_data = nullptr);
 
/// Restores default bad alloc error handling behavior.
void remove_bad_alloc_error_handler();
 
void install_out_of_memory_new_handler();
 
/// Reports a bad alloc error, calling any user defined bad alloc
/// error handler. In contrast to the generic 'report_fatal_error'
/// functions, this function might not terminate, e.g. the user
/// defined error handler throws an exception, but it won't return.
///
/// Note: When throwing an exception in the bad alloc handler, make sure that
/// the following unwind succeeds, e.g. do not trigger additional allocations
/// in the unwind chain.
///
/// If no error handler is installed (default), throws a bad_alloc exception
/// if LLVM is compiled with exception support. Otherwise prints the error
/// to standard error and calls abort().
[[noreturn]] void report_bad_alloc_error(const char *Reason,
                                         bool GenCrashDiag = true);
 
/// This function calls abort(), and prints the optional message to stderr.
/// Use the llvm_unreachable macro (that adds location info), instead of
/// calling this function directly.
[[noreturn]] void
llvm_unreachable_internal(const char *msg = nullptr, const char *file = nullptr,
                          unsigned line = 0);
}
 
/// Marks that the current location is not supposed to be reachable.
/// In !NDEBUG builds, prints the message and location info to stderr.
/// In NDEBUG builds, if the platform does not support a builtin unreachable
/// then we call an internal LLVM runtime function. Otherwise the behavior is
/// controlled by the CMake flag
///   -DLLVM_UNREACHABLE_OPTIMIZE
/// * When "ON" (default) llvm_unreachable() becomes an optimizer hint
///   that the current location is not supposed to be reachable: the hint
///   turns such code path into undefined behavior.  On compilers that don't
///   support such hints, prints a reduced message instead and aborts the
///   program.
/// * When "OFF", a builtin_trap is emitted instead of an
//    optimizer hint or printing a reduced message.
///
/// Use this instead of assert(0). It conveys intent more clearly, suppresses
/// diagnostics for unreachable code paths, and allows compilers to omit
/// unnecessary code.
#ifndef NDEBUG
#define llvm_unreachable(msg) \
  ::llvm::llvm_unreachable_internal(msg, __FILE__, __LINE__)
#elif !defined(LLVM_BUILTIN_UNREACHABLE)
#define llvm_unreachable(msg) ::llvm::llvm_unreachable_internal()
#elif LLVM_UNREACHABLE_OPTIMIZE
#define llvm_unreachable(msg) LLVM_BUILTIN_UNREACHABLE
#else
#define llvm_unreachable(msg)                                                  \
  do {                                                                         \
    LLVM_BUILTIN_TRAP;                                                         \
    LLVM_BUILTIN_UNREACHABLE;                                                  \
  } while (false)
#endif
 
#endif