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ErrorHandling.h
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00001 //===- llvm/Support/ErrorHandling.h - Fatal error handling ------*- C++ -*-===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file defines an API used to indicate fatal error conditions.  Non-fatal
00011 // errors (most of them) should be handled through LLVMContext.
00012 //
00013 //===----------------------------------------------------------------------===//
00014 
00015 #ifndef LLVM_SUPPORT_ERRORHANDLING_H
00016 #define LLVM_SUPPORT_ERRORHANDLING_H
00017 
00018 #include "llvm/ADT/StringRef.h"
00019 #include "llvm/Support/Compiler.h"
00020 #include <string>
00021 
00022 namespace llvm {
00023   class Twine;
00024 
00025   /// An error handler callback.
00026   typedef void (*fatal_error_handler_t)(void *user_data,
00027                                         const std::string& reason,
00028                                         bool gen_crash_diag);
00029 
00030   /// install_fatal_error_handler - Installs a new error handler to be used
00031   /// whenever a serious (non-recoverable) error is encountered by LLVM.
00032   ///
00033   /// If no error handler is installed the default is to print the error message
00034   /// to stderr, and call exit(1).  If an error handler is installed then it is
00035   /// the handler's responsibility to log the message, it will no longer be
00036   /// printed to stderr.  If the error handler returns, then exit(1) will be
00037   /// called.
00038   ///
00039   /// It is dangerous to naively use an error handler which throws an exception.
00040   /// Even though some applications desire to gracefully recover from arbitrary
00041   /// faults, blindly throwing exceptions through unfamiliar code isn't a way to
00042   /// achieve this.
00043   ///
00044   /// \param user_data - An argument which will be passed to the install error
00045   /// handler.
00046   void install_fatal_error_handler(fatal_error_handler_t handler,
00047                                    void *user_data = nullptr);
00048 
00049   /// Restores default error handling behaviour.
00050   void remove_fatal_error_handler();
00051 
00052   /// ScopedFatalErrorHandler - This is a simple helper class which just
00053   /// calls install_fatal_error_handler in its constructor and
00054   /// remove_fatal_error_handler in its destructor.
00055   struct ScopedFatalErrorHandler {
00056     explicit ScopedFatalErrorHandler(fatal_error_handler_t handler,
00057                                      void *user_data = nullptr) {
00058       install_fatal_error_handler(handler, user_data);
00059     }
00060 
00061     ~ScopedFatalErrorHandler() { remove_fatal_error_handler(); }
00062   };
00063 
00064   /// Reports a serious error, calling any installed error handler. These
00065   /// functions are intended to be used for error conditions which are outside
00066   /// the control of the compiler (I/O errors, invalid user input, etc.)
00067   ///
00068   /// If no error handler is installed the default is to print the message to
00069   /// standard error, followed by a newline.
00070   /// After the error handler is called this function will call exit(1), it 
00071   /// does not return.
00072   LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const char *reason,
00073                                                   bool gen_crash_diag = true);
00074   LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const std::string &reason,
00075                                                   bool gen_crash_diag = true);
00076   LLVM_ATTRIBUTE_NORETURN void report_fatal_error(StringRef reason,
00077                                                   bool gen_crash_diag = true);
00078   LLVM_ATTRIBUTE_NORETURN void report_fatal_error(const Twine &reason,
00079                                                   bool gen_crash_diag = true);
00080 
00081   /// This function calls abort(), and prints the optional message to stderr.
00082   /// Use the llvm_unreachable macro (that adds location info), instead of
00083   /// calling this function directly.
00084   LLVM_ATTRIBUTE_NORETURN void
00085   llvm_unreachable_internal(const char *msg=nullptr, const char *file=nullptr,
00086                             unsigned line=0);
00087 }
00088 
00089 /// Marks that the current location is not supposed to be reachable.
00090 /// In !NDEBUG builds, prints the message and location info to stderr.
00091 /// In NDEBUG builds, becomes an optimizer hint that the current location
00092 /// is not supposed to be reachable.  On compilers that don't support
00093 /// such hints, prints a reduced message instead.
00094 ///
00095 /// Use this instead of assert(0).  It conveys intent more clearly and
00096 /// allows compilers to omit some unnecessary code.
00097 #ifndef NDEBUG
00098 #define llvm_unreachable(msg) \
00099   ::llvm::llvm_unreachable_internal(msg, __FILE__, __LINE__)
00100 #elif defined(LLVM_BUILTIN_UNREACHABLE)
00101 #define llvm_unreachable(msg) LLVM_BUILTIN_UNREACHABLE
00102 #else
00103 #define llvm_unreachable(msg) ::llvm::llvm_unreachable_internal()
00104 #endif
00105 
00106 #endif