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 
21 namespace llvm {
22 class StringRef;
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 
~ScopedFatalErrorHandlerScopedFatalErrorHandler61     ~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