c++ - 错误 : expected primary-expression before ';' token

Question

我得到了错误

error: expected primary-expression before ';' token

当我尝试编译以下代码时。问题是什么？

#include <iostream>
#include <stdexcept>
#include <exception>
using namespace std;

class MyException : public std::invalid_argument{};

int main() {
    try {
        throw MyException; //here is the problem
    }
    catch (...){
    }

    return 0;
}

我也试过这段代码

#include <iostream>
#include <stdexcept>
#include <exception>
using namespace std;

class MyException : public std::invalid_argument{};

int main() {
    try {
        throw MyException(); //here is the problem
    }
    catch (...){
    }

    return 0;
}

但是我又遇到了一个错误

main.cpp: In constructor ‘MyException::MyException()’:
main.cpp:6:7: error: no matching function for call to ‘std::invalid_argument::invalid_argument()’
main.cpp:6:7: note: candidates are:
In file included from main.cpp:2:0:
/usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/stdexcept:86:14: note: std::invalid_argument::invalid_argument(const string&)
/usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/stdexcept:86:14: note:   candidate expects 1 argument, 0 provided
/usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/stdexcept:83:9: note: std::invalid_argument::invalid_argument(const std::invalid_argument&)
/usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/stdexcept:83:9: note:   candidate expects 1 argument, 0 provided
main.cpp: In function ‘int main()’:
main.cpp:10:27: note: synthesized method ‘MyException::MyException()’ first required here 

Answer 1

你需要创建一个实际的对象来抛出:

throw MyException();

没有括号 MyException 只是类型，它不会创建对象。