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  1. // Scroll down to line 85 for example of usage
  2. // _________________[uncaught_exception_count.hpp]_____________________ //
  3.  
  4. //             Copyright Evgeny Panasyuk 2012.
  5. // Distributed under the Boost Software License, Version 1.0.
  6. //    (See accompanying file LICENSE_1_0.txt or copy at
  7. //          http://w...content-available-to-author-only...t.org/LICENSE_1_0.txt)
  8.  
  9. // e-mail: E?????[dot]P???????[at]gmail.???
  10.  
  11. #ifndef BOOST_UNCAUGHT_EXCEPTION_COUNT_HPP_39A1E90FC11647e08D5F6ED16CD34B34
  12. #define BOOST_UNCAUGHT_EXCEPTION_COUNT_HPP_39A1E90FC11647e08D5F6ED16CD34B34
  13.  
  14. #if defined(_MSC_VER) || defined(__GNUG__) || defined(__CLANG__)
  15.     #define BOOST_UNCAUGHT_EXCEPTION_COUNT_SUPPORTED 1
  16. #endif
  17.  
  18. namespace boost
  19. {
  20.     namespace exception_detail
  21.     {
  22.         template<typename To> inline
  23.         To *unrelated_pointer_cast(void *from)
  24.         {
  25.             return static_cast<To*>(from);
  26.         }
  27.     }
  28.  
  29.     // uncaught_exception_count is a function similar to std::uncaught_exception from standard library,
  30.     // but instead of boolean result it returns unsigned int showing current count of uncaught exceptions.
  31.  
  32. #if defined(_MSC_VER)
  33.     namespace exception_detail
  34.     {
  35.         extern "C" char * __cdecl _getptd();
  36.     }
  37.     inline unsigned uncaught_exception_count()
  38.     {
  39.         // MSVC specific. Tested on {MSVC2005SP1,MSVC2008SP1,MSVC2010SP1,MSVC2012}x{x32,x64}.
  40.         return *exception_detail::unrelated_pointer_cast<unsigned>
  41.         (
  42.             exception_detail::_getptd() + (sizeof(void*)==8 ? 0x100 : 0x90) 
  43.         );
  44.     }
  45. #elif defined(__GNUG__) || defined(__CLANG__)
  46.     namespace exception_detail
  47.     {
  48.         extern "C" char * __cxa_get_globals();
  49.     }
  50.     inline unsigned uncaught_exception_count()
  51.     {
  52.         // Tested on {Clang 3.2,GCC 3.4.6,GCC 4.1.2,GCC 4.4.6,GCC 4.4.7}x{x32,x64}
  53.         return *exception_detail::unrelated_pointer_cast<unsigned>
  54.         (
  55.             exception_detail::__cxa_get_globals() + (sizeof(void*)==8 ? 0x8 : 0x4)
  56.         );
  57.     }
  58. #endif
  59.  
  60.     // Within one scope uncaught_exception_count can be changed only by +1.
  61.     // uncaught_exception_count_latch is primitive which helps to determine such transition.
  62.     //     Internally it stores and compares only last bit of uncaught_exception_count value
  63. #ifdef BOOST_UNCAUGHT_EXCEPTION_COUNT_SUPPORTED
  64.     class uncaught_exception_count_latch
  65.     {
  66.             unsigned char enter_state;
  67.         public:
  68.             uncaught_exception_count_latch()
  69.                 : enter_state(static_cast<unsigned char>( uncaught_exception_count() & 1 ))
  70.             {
  71.             }
  72.             bool transitioned() const
  73.             {
  74.                 return enter_state != ( uncaught_exception_count() & 1 );
  75.             }
  76.     };
  77. #endif
  78.  
  79. }
  80.  
  81. #endif
  82.  
  83. // ______________[end of uncaught_exception_count.hpp]_________________ //
  84.  
  85. #include <iostream>
  86. #include <ostream>
  87.  
  88. using namespace std;
  89.  
  90. void success()
  91. {
  92.     cout << "\tsuccess()" << endl;
  93. }
  94. void failure()
  95. {
  96.     cout << "\tfailure()" << endl;
  97. }
  98.  
  99. class ScopeGuard
  100. {
  101.     bool commited;
  102. public:
  103.     ScopeGuard() : commited(false) {}
  104.     bool commit()
  105.     {
  106.         commited = true;
  107.     }
  108.     ~ScopeGuard()
  109.     {
  110.         if(commited)
  111.             success();
  112.         else
  113.             failure();
  114.     }
  115. };
  116.  
  117. class ScopeAction
  118. {
  119.     boost::uncaught_exception_count_latch exception_state;
  120. public:
  121.     ~ScopeAction()
  122.     {
  123.         if(exception_state.transitioned())
  124.             failure();
  125.         else
  126.             success();
  127.     }
  128. };
  129.  
  130. int main()
  131. {
  132.     {
  133.         cout << "ScopeGuard:" << endl;
  134.         try
  135.         {
  136.             ScopeGuard guard;
  137.             throw 1;
  138.             guard.commit();
  139.         }
  140.         catch(int) {}
  141.         {
  142.             ScopeGuard guard;
  143.             // ...
  144.             guard.commit();
  145.         }
  146.     }
  147.     {
  148.         cout << "ScopeAction:" << endl;
  149.         try
  150.         {
  151.             ScopeAction guard;
  152.             throw 1;
  153.         }
  154.         catch(int) {}
  155.         {
  156.             ScopeAction guard;
  157.             // ...
  158.         }
  159.     }
  160. }
Success #stdin #stdout 0s 2984KB
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Standard input is empty
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ScopeGuard:
	failure()
	success()
ScopeAction:
	failure()
	success()
https://ideone.com/jCCew0
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
secret

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