1//===- llvm/Support/ErrorHandling.h - Fatal error handling ------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines an API used to indicate fatal error conditions.  Non-fatal
11// errors (most of them) should be handled through LLVMContext.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_SUPPORT_ERRORHANDLING_H
16#define LLVM_SUPPORT_ERRORHANDLING_H
17
18#include "llvm/ADT/StringRef.h"
19#include "llvm/Support/Compiler.h"
20#include <string>
21
22namespace llvm {
23  class Twine;
24
25  /// An error handler callback.
26  typedef void (*fatal_error_handler_t)(void *user_data,
27                                        const std::string& reason,
28                                        bool gen_crash_diag);
29
30  /// install_fatal_error_handler - Installs a new error handler to be used
31  /// whenever a serious (non-recoverable) error is encountered by LLVM.
32  ///
33  /// If no error handler is installed the default is to print the error message
34  /// to stderr, and call exit(1).  If an error handler is installed then it is
35  /// the handler's responsibility to log the message, it will no longer be
36  /// printed to stderr.  If the error handler returns, then exit(1) will be
37  /// called.
38  ///
39  /// It is dangerous to naively use an error handler which throws an exception.
40  /// Even though some applications desire to gracefully recover from arbitrary
41  /// faults, blindly throwing exceptions through unfamiliar code isn't a way to
42  /// achieve this.
43  ///
44  /// \param user_data - An argument which will be passed to the install error
45  /// handler.
46  void install_fatal_error_handler(fatal_error_handler_t handler,
47                                   void *user_data = nullptr);
48
49  /// Restores default error handling behaviour.
50  void remove_fatal_error_handler();
51
52  /// ScopedFatalErrorHandler - This is a simple helper class which just
53  /// calls install_fatal_error_handler in its constructor and
54  /// remove_fatal_error_handler in its destructor.
55  struct ScopedFatalErrorHandler {
56    explicit ScopedFatalErrorHandler(fatal_error_handler_t handler,
57                                     void *user_data = nullptr) {
58      install_fatal_error_handler(handler, user_data);
59    }
60
61    ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
62  };
63
64  /// Reports a serious error, calling any installed error handler. These
65  /// functions are intended to be used for error conditions which are outside
66  /// the control of the compiler (I/O errors, invalid user input, etc.)
67  ///
68  /// If no error handler is installed the default is to print the message to
69  /// standard error, followed by a newline.
70  /// After the error handler is called this function will call exit(1), it
71  /// does not return.
72  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const char *reason,
73                                                  bool gen_crash_diag = true);
74  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const std::string &reason,
75                                                  bool gen_crash_diag = true);
76  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(StringRef reason,
77                                                  bool gen_crash_diag = true);
78  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const Twine &reason,
79                                                  bool gen_crash_diag = true);
80
81  /// This function calls abort(), and prints the optional message to stderr.
82  /// Use the llvm_unreachable macro (that adds location info), instead of
83  /// calling this function directly.
84  LLVM_ATTRIBUTE_NORETURN void
85  llvm_unreachable_internal(const char *msg=nullptr, const char *file=nullptr,
86                            unsigned line=0);
87}
88
89/// Marks that the current location is not supposed to be reachable.
90/// In !NDEBUG builds, prints the message and location info to stderr.
91/// In NDEBUG builds, becomes an optimizer hint that the current location
92/// is not supposed to be reachable.  On compilers that don't support
93/// such hints, prints a reduced message instead.
94///
95/// Use this instead of assert(0).  It conveys intent more clearly and
96/// allows compilers to omit some unnecessary code.
97#ifndef NDEBUG
98#define llvm_unreachable(msg) \
99  ::llvm::llvm_unreachable_internal(msg, __FILE__, __LINE__)
100#elif defined(LLVM_BUILTIN_UNREACHABLE)
101#define llvm_unreachable(msg) LLVM_BUILTIN_UNREACHABLE
102#else
103#define llvm_unreachable(msg) ::llvm::llvm_unreachable_internal()
104#endif
105
106#endif
107