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      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 
     22 namespace 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