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 
77   virtual ~exception() _NOEXCEPT;
78   virtual const char* what() const _NOEXCEPT;
79 };
80 
81 class _LIBCPP_EXPORTED_FROM_ABI bad_exception : public exception {
82 public:
83   _LIBCPP_HIDE_FROM_ABI bad_exception() _NOEXCEPT {}
84   ~bad_exception() _NOEXCEPT override;
85   const char* what() const _NOEXCEPT override;
86 };
87 #endif // !_LIBCPP_ABI_VCRUNTIME
88 
89 } // namespace std
90 
91 #endif // _LIBCPP___EXCEPTION_EXCEPTION_H
92