A throw-expression with no operand in C++

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本文介绍了 C++ 中如何使用空抛出表达式重新抛出当前正在处理的异常，并解释了这种表达式只应在 catch 处理程序或从 catch 处理程序内部调用的函数中出现的原因。此外，还展示了如何声明不抛出任何异常的函数。

A throw-expression with no operand re-throws the exception currently being handled. Such an expression should appear only in a catch handler or in a function called from within a catch handler. The re-thrown exception object is the original exception object (not a copy). For example:

try {
    throw CSomeOtherException();
}
catch(...) {  // Handle all exceptions
    // Respond (perhaps only partially) to exception
    // ...
    throw;       // Pass exception to some other handler
}

An empty throw statement tells the compiler that the function does not throw any exceptions. It is the equivalent to using __declspec(nothrow). For example:

// exceptions_trycatchandthrowstatements3.cpp 
void empty() throw()
{
   puts("In empty()");
}

void with_type() throw(int)
{
   puts("Will throw an int");
   throw(1);
}

int main()
{
   try {
       empty();
       with_type();
   }catch (int){
       puts("Caught an int");
   }
}