来源：https://en.cppreference.com/w/cpp/language/throw

throw 异常

#include <stdexcept>

throw std::runtime_error("error");

完整示例

#include <iostream>
#include <stdexcept>

struct A
{
    int n;

    A(int n = 0): n(n) { std::cout << "A(" << n << ") constructed successfully\n"; }
    ~A() { std::cout << "A(" << n << ") destroyed\n"; }
};

int foo()
{
    throw std::runtime_error("error");
}

struct B
{
    A a1, a2, a3;

    B() try : a1(1), a2(foo()), a3(3)
    {
        std::cout << "B constructed successfully\n";
    }
    catch(...)
    {
        std::cout << "B::B() exiting with exception\n";
    }

    ~B() { std::cout << "B destroyed\n"; }
};

struct C : A, B
{
    C() try
    {
        std::cout << "C::C() completed successfully\n";
    }
    catch(...)
    {
        std::cout << "C::C() exiting with exception\n";
    }

    ~C() { std::cout << "C destroyed\n"; }
};

int main () try
{
    // creates the A base subobject
    // creates the a1 member of B
    // fails to create the a2 member of B
    // unwinding destroys the a1 member of B
    // unwinding destroys the A base subobject
    C c;
}
catch (const std::exception& e)
{
    std::cout << "main() failed to create C with: " << e.what();
}