C++ 终止处理程序能否引发异常？

以下程序的定义行为是什么（如果有）

#include <iostream>
#include <exception>
#include <cstdlib>

void i_throw()
{
    std::cout << "i_throw()" << std::endl;
    // std::terminate() is noexcept so if the terminate handler throws...
    // then the terminate handler is called...
    // std::terminate is [[noreturn]] so don't return
    try
    {
        throw 7;
    }
    catch(...)
    {
        std::cout << "caught exception, re-throw()-ing" << std::endl;
        throw;
    }
    std::cout << "got here!" << std::endl;
    std::abort();
}

int main()
{
    std::set_terminate(i_throw);
    throw;
    std::terminate();
}

示例在前几条注释后编辑

---

（我不知道为什么我有

throw；

和

std:：terminate（）；

。我不想改变这个例子，所以就假设只有这两个代码片段中的一个存在。）

以上问题可以归结为理解以下两个代码片段的行为

示例1:无活动异常抛出

int main()
{
    try{
        throw;
    }catch(...){
        std::cout<<"caught"<<endl;  //we never reach here
    }
    return 0;
}

int main()
{
    try{
        throw 7;
    }catch(...){
        std::cout<<"caught"<<endl;  //will be caught
    }
    return 0;
}

示例2:抛出活动异常

int main()
{
    try{
        throw;
    }catch(...){
        std::cout<<"caught"<<endl;  //we never reach here
    }
    return 0;
}

int main()
{
    try{
        throw 7;
    }catch(...){
        std::cout<<"caught"<<endl;  //will be caught
    }
    return 0;
}

如果生成代码的程序集（

g++-S选项

）。您将注意到以下cxx_abi调用throw vs throw 7

抛出转换为
call\uuuucxa\urethrow

extern "C" void
__cxxabiv1::__cxa_throw (void *obj, std::type_info *tinfo,
             void (_GLIBCXX_CDTOR_CALLABI *dest) (void *))
{
  PROBE2 (throw, obj, tinfo);

  __cxa_eh_globals *globals = __cxa_get_globals ();
  globals->uncaughtExceptions += 1;

  // code removed for brevity 
  //.......
  // Below code throws an exception to be caught by caller

  #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
    _Unwind_SjLj_RaiseException (&header->exc.unwindHeader);
  #else
    _Unwind_RaiseException (&header->exc.unwindHeader);
  #endif

  // Some sort of unwinding error.  Note that terminate is a handler.
  __cxa_begin_catch (&header->exc.unwindHeader);
  std::terminate ();
}

extern "C" void
__cxxabiv1::__cxa_rethrow ()
{
  __cxa_eh_globals *globals = __cxa_get_globals ();
  __cxa_exception *header = globals->caughtExceptions; // We are not re

  globals->uncaughtExceptions += 1;

  // Watch for luser rethrowing with no active exception.
  if (header)
    {
      // Code removed for brevity
      // .....
      // Below code rethrows the exception
      #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
      _Unwind_SjLj_Resume_or_Rethrow (&header->unwindHeader);
      #else
      #if defined(_LIBUNWIND_STD_ABI)
      _Unwind_RaiseException (&header->unwindHeader);
      #else
      _Unwind_Resume_or_Rethrow (&header->unwindHeader);
      #endif
      #endif
    }
  std::terminate ();
}

及

throw7转换为
call\uuucxa\uthrow

这是
\uucxa\uthrow

extern "C" void
__cxxabiv1::__cxa_throw (void *obj, std::type_info *tinfo,
             void (_GLIBCXX_CDTOR_CALLABI *dest) (void *))
{
  PROBE2 (throw, obj, tinfo);

  __cxa_eh_globals *globals = __cxa_get_globals ();
  globals->uncaughtExceptions += 1;

  // code removed for brevity 
  //.......
  // Below code throws an exception to be caught by caller

  #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
    _Unwind_SjLj_RaiseException (&header->exc.unwindHeader);
  #else
    _Unwind_RaiseException (&header->exc.unwindHeader);
  #endif

  // Some sort of unwinding error.  Note that terminate is a handler.
  __cxa_begin_catch (&header->exc.unwindHeader);
  std::terminate ();
}

extern "C" void
__cxxabiv1::__cxa_rethrow ()
{
  __cxa_eh_globals *globals = __cxa_get_globals ();
  __cxa_exception *header = globals->caughtExceptions; // We are not re

  globals->uncaughtExceptions += 1;

  // Watch for luser rethrowing with no active exception.
  if (header)
    {
      // Code removed for brevity
      // .....
      // Below code rethrows the exception
      #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
      _Unwind_SjLj_Resume_or_Rethrow (&header->unwindHeader);
      #else
      #if defined(_LIBUNWIND_STD_ABI)
      _Unwind_RaiseException (&header->unwindHeader);
      #else
      _Unwind_Resume_or_Rethrow (&header->unwindHeader);
      #endif
      #endif
    }
  std::terminate ();
}

因此，在OP Codethrow 7中将被相应的
catch（…）
捕获，并将被
throw重新抛出

这是
\uuuucxa\uuuuuu rethrow

extern "C" void
__cxxabiv1::__cxa_throw (void *obj, std::type_info *tinfo,
             void (_GLIBCXX_CDTOR_CALLABI *dest) (void *))
{
  PROBE2 (throw, obj, tinfo);

  __cxa_eh_globals *globals = __cxa_get_globals ();
  globals->uncaughtExceptions += 1;

  // code removed for brevity 
  //.......
  // Below code throws an exception to be caught by caller

  #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
    _Unwind_SjLj_RaiseException (&header->exc.unwindHeader);
  #else
    _Unwind_RaiseException (&header->exc.unwindHeader);
  #endif

  // Some sort of unwinding error.  Note that terminate is a handler.
  __cxa_begin_catch (&header->exc.unwindHeader);
  std::terminate ();
}

extern "C" void
__cxxabiv1::__cxa_rethrow ()
{
  __cxa_eh_globals *globals = __cxa_get_globals ();
  __cxa_exception *header = globals->caughtExceptions; // We are not re

  globals->uncaughtExceptions += 1;

  // Watch for luser rethrowing with no active exception.
  if (header)
    {
      // Code removed for brevity
      // .....
      // Below code rethrows the exception
      #ifdef _GLIBCXX_SJLJ_EXCEPTIONS
      _Unwind_SjLj_Resume_or_Rethrow (&header->unwindHeader);
      #else
      #if defined(_LIBUNWIND_STD_ABI)
      _Unwind_RaiseException (&header->unwindHeader);
      #else
      _Unwind_Resume_or_Rethrow (&header->unwindHeader);
      #endif
      #endif
    }
  std::terminate ();
}

在这两种情况下，我们可以看到，
std:：terminate（）
尚未从
\uuuuucxx.*
调用。在被上面的abi抛出后，我们在代码中的以下位置

void
__cxxabiv1::__terminate (std::terminate_handler handler) throw ()
{
  __try 
    {
      handler ();      // Our handler has thrown an int exception
      std::abort ();
    } 
  __catch(...)  // Exception is caught here and process is aborted.
    { std::abort (); } 
}

void
std::terminate () throw()
{
  __terminate (get_terminate ());
}

有关终止代码的信息，请参阅

void
__cxxabiv1::__terminate (std::terminate_handler handler) throw ()
{
  __try 
    {
      handler ();      // Our handler has thrown an int exception
      std::abort ();
    } 
  __catch(...)  // Exception is caught here and process is aborted.
    { std::abort (); } 
}

void
std::terminate () throw()
{
  __terminate (get_terminate ());
}

摘要

根据我的理解，从处理程序重新抛出异常会导致在
\uuuucxxabiv1:：\uuuu terminate
中捕获重新抛出的异常。它在其中调用
abort（）
。显然，
std:：terminate（）
[from\uuucxa\u rethrow]方法没有出现在图中，这就是为什么控件从未到达
std:：cout此程序导致无限递归的原因。与任何其他无限递归一样，由于耗尽了实现的资源限制（1.4/（2.1）），它最终将异常结束。请注意，这里没有抛出异常，
terminate
的
noexcept
规范与此无关。执行
throw没有操作数，而没有处理异常调用
terminate（）
（5.17/4）@IgorTandetnik我想我在你的评论中看到了答案。你能解释一下没有抛出异常是什么意思吗？终止处理程序是终止程序执行所必需的。你的没有。@t.C.不过它会的。这是否意味着有效的终止处理程序不能允许异常冒泡？@praxelitic 1）代码中有一条注释表明OP认为有异常被抛出，调用
terminate（）
是由于异常在
terminate
中传播，后者是
noexcept
。但是
抛出无参数仅在当前正在处理异常时抛出异常；否则，它只直接调用
terminate
。后一种情况实际上发生在示例中。