ErrorHandling.h revision a70d37154f528d30af1c320fd2888974e949dac4 
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 <string>
20
21namespace llvm {
22  class Twine;
23
24  /// An error handler callback.
25  typedef void (*fatal_error_handler_t)(void *user_data,
26                                        const std::string& reason);
27
28  /// install_fatal_error_handler - Installs a new error handler to be used
29  /// whenever a serious (non-recoverable) error is encountered by LLVM.
30  ///
31  /// If you are using llvm_start_multithreaded, you should register the handler
32  /// before doing that.
33  ///
34  /// If no error handler is installed the default is to print the error message
35  /// to stderr, and call exit(1).  If an error handler is installed then it is
36  /// the handler's responsibility to log the message, it will no longer be
37  /// printed to stderr.  If the error handler returns, then exit(1) will be
38  /// called.
39  ///
40  /// It is dangerous to naively use an error handler which throws an exception.
41  /// Even though some applications desire to gracefully recover from arbitrary
42  /// faults, blindly throwing exceptions through unfamiliar code isn't a way to
43  /// achieve this.
44  ///
45  /// \param user_data - An argument which will be passed to the install error
46  /// handler.
47  void install_fatal_error_handler(fatal_error_handler_t handler,
48                                   void *user_data = 0);
49
50  /// Restores default error handling behaviour.
51  /// This must not be called between llvm_start_multithreaded() and
52  /// llvm_stop_multithreaded().
53  void remove_fatal_error_handler();
54
55  /// ScopedFatalErrorHandler - This is a simple helper class which just
56  /// calls install_fatal_error_handler in its constructor and
57  /// remove_fatal_error_handler in its destructor.
58  struct ScopedFatalErrorHandler {
59    explicit ScopedFatalErrorHandler(fatal_error_handler_t handler,
60                                     void *user_data = 0) {
61      install_fatal_error_handler(handler, user_data);
62    }
63
64    ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
65  };
66
67  /// Reports a serious error, calling any installed error handler. These
68  /// functions are intended to be used for error conditions which are outside
69  /// the control of the compiler (I/O errors, invalid user input, etc.)
70  ///
71  /// If no error handler is installed the default is to print the message to
72  /// standard error, followed by a newline.
73  /// After the error handler is called this function will call exit(1), it
74  /// does not return.
75  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const char *reason);
76  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const std::string &reason);
77  LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const Twine &reason);
78
79  /// This function calls abort(), and prints the optional message to stderr.
80  /// Use the llvm_unreachable macro (that adds location info), instead of
81  /// calling this function directly.
82  LLVM_ATTRIBUTE_NORETURN void llvm_unreachable_internal(const char *msg=0,
83                                                         const char *file=0,
84                                                         unsigned line=0);
85}
86
87/// Prints the message and location info to stderr in !NDEBUG builds.
88/// This is intended to be used for "impossible" situations that imply
89/// a bug in the compiler.
90///
91/// In NDEBUG mode it only prints "UNREACHABLE executed".
92/// Use this instead of assert(0), so that the compiler knows this path
93/// is not reachable even for NDEBUG builds.
94#ifndef NDEBUG
95#define llvm_unreachable(msg) \
96  ::llvm::llvm_unreachable_internal(msg, __FILE__, __LINE__)
97#else
98#define llvm_unreachable(msg) ::llvm::llvm_unreachable_internal()
99#endif
100
101#endif
102