libcxx/include/__exception/exception.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___EXCEPTION_EXCEPTION_H
  10 #define _LIBCPP___EXCEPTION_EXCEPTION_H
  11
  12 #include <__config>
  13
  14 // <vcruntime_exception.h> defines its own std::exception and std::bad_exception types,
  15 // which we use in order to be ABI-compatible with other STLs on Windows.
  16 #if defined(_LIBCPP_ABI_VCRUNTIME)
  17 #  include <vcruntime_exception.h>
  18 #endif
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #  pragma GCC system_header
  22 #endif
  23
  24 namespace std { // purposefully not using versioning namespace
  25
  26 #if defined(_LIBCPP_ABI_VCRUNTIME) && (!defined(_HAS_EXCEPTIONS) || _HAS_EXCEPTIONS != 0)
  27 // The std::exception class was already included above, but we're explicit about this condition here for clarity.
  28
  29 #elif defined(_LIBCPP_ABI_VCRUNTIME) && _HAS_EXCEPTIONS == 0
  30 // However, <vcruntime_exception.h> does not define std::exception and std::bad_exception
  31 // when _HAS_EXCEPTIONS == 0.
  32 //
  33 // Since libc++ still wants to provide the std::exception hierarchy even when _HAS_EXCEPTIONS == 0
  34 // (after all those are simply types like any other), we define an ABI-compatible version
  35 // of the VCRuntime std::exception and std::bad_exception types in that mode.
  36
  37 struct __std_exception_data {
  38   char const* _What;
  39   bool _DoFree;
  40 };
  41
  42 class exception { // base of all library exceptions
  43 public:
  44   exception() _NOEXCEPT : __data_() {}
  45
  46   explicit exception(char const* __message) _NOEXCEPT : __data_() {
  47     __data_._What   = __message;
  48     __data_._DoFree = true;
  49   }
  50
  51   exception(exception const&) _NOEXCEPT {}
  52
  53   exception& operator=(exception const&) _NOEXCEPT { return *this; }
  54
  55   virtual ~exception() _NOEXCEPT {}
  56
  57   virtual char const* what() const _NOEXCEPT { return __data_._What ? __data_._What : "Unknown exception"; }
  58
  59 private:
  60   __std_exception_data __data_;
  61 };
  62
  63 class bad_exception : public exception {
  64 public:
  65   bad_exception() _NOEXCEPT : exception("bad exception") {}
  66 };
  67
  68 #else  // !defined(_LIBCPP_ABI_VCRUNTIME)
  69 // On all other platforms, we define our own std::exception and std::bad_exception types
  70 // regardless of whether exceptions are turned on as a language feature.
  71
  72 class _LIBCPP_EXPORTED_FROM_ABI exception {
  73 public:
  74   _LIBCPP_HIDE_FROM_ABI exception() _NOEXCEPT {}
  75   _LIBCPP_HIDE_FROM_ABI exception(const exception&) _NOEXCEPT            = default;
  76   _LIBCPP_HIDE_FROM_ABI exception& operator=(const exception&) _NOEXCEPT = default;
  77
  78   virtual ~exception() _NOEXCEPT;
  79   virtual const char* what() const _NOEXCEPT;
  80 };
  81
  82 class _LIBCPP_EXPORTED_FROM_ABI bad_exception : public exception {
  83 public:
  84   _LIBCPP_HIDE_FROM_ABI bad_exception() _NOEXCEPT {}
  85   _LIBCPP_HIDE_FROM_ABI bad_exception(const bad_exception&) _NOEXCEPT            = default;
  86   _LIBCPP_HIDE_FROM_ABI bad_exception& operator=(const bad_exception&) _NOEXCEPT = default;
  87   ~bad_exception() _NOEXCEPT override;
  88   const char* what() const _NOEXCEPT override;
  89 };
  90 #endif // !_LIBCPP_ABI_VCRUNTIME
  91
  92 } // namespace std
  93
  94 #endif // _LIBCPP___EXCEPTION_EXCEPTION_H