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/Support/Compiler.h"
19#include "llvm/ADT/StringRef.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
29  /// install_fatal_error_handler - Installs a new error handler to be used
30  /// whenever a serious (non-recoverable) error is encountered by LLVM.
31  ///
32  /// If you are using llvm_start_multithreaded, you should register the handler
33  /// before doing that.
34  ///
35  /// If no error handler is installed the default is to print the error message
36  /// to stderr, and call exit(1).  If an error handler is installed then it is
37  /// the handler's responsibility to log the message, it will no longer be
38  /// printed to stderr.  If the error handler returns, then exit(1) will be
39  /// called.
40  ///
41  /// It is dangerous to naively use an error handler which throws an exception.
42  /// Even though some applications desire to gracefully recover from arbitrary
43  /// faults, blindly throwing exceptions through unfamiliar code isn't a way to
44  /// achieve this.
45  ///
46  /// \param user_data - An argument which will be passed to the install error
47  /// handler.
48  void install_fatal_error_handler(fatal_error_handler_t handler,
49                                   void *user_data = 0);
50
51  /// Restores default error handling behaviour.
52  /// This must not be called between llvm_start_multithreaded() and
53  /// llvm_stop_multithreaded().
54  void remove_fatal_error_handler();
55
56  /// ScopedFatalErrorHandler - This is a simple helper class which just
57  /// calls install_fatal_error_handler in its constructor and
58  /// remove_fatal_error_handler in its destructor.
59  struct ScopedFatalErrorHandler {
60    explicit ScopedFatalErrorHandler(fatal_error_handler_t handler,
61                                     void *user_data = 0) {
62      install_fatal_error_handler(handler, user_data);
63    }
64
65    ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
66  };
67
68  /// Reports a serious error, calling any installed error handler. These
69  /// functions are intended to be used for error conditions which are outside
70  /// the control of the compiler (I/O errors, invalid user input, etc.)
71  ///
72  /// If no error handler is installed the default is to print the message to
73  /// standard error, followed by a newline.
74  /// After the error handler is called this function will call exit(1), it
75  /// does not return.
76  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const char *reason);
77  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const std::string &reason);
78  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(StringRef reason);
79  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const Twine &reason);
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 llvm_unreachable_internal(const char *msg=0,
85                                                         const char *file=0,
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