AddressSanitizer GCC 4.8的双重免费错误

Question

Consider the following toy program( prog.cpp ):

class A {
public:
    vector<int> vec;
    A() noexcept {}
    A(vector<int> s) : vec(s) {}
};

class B {

private:
    vector<atomic<A>> a_table;

public:
    B(int capacity) : a_table(capacity) {}

    void update(int index) {
        A newValue(vector<int>(10,1));
        a_table[index].store(newValue);
    }
};


int main(int argc, char** argv) 
{
B b(5);
b.update(2);
return 0;
}

This when compiled normally ( g++ prog.cpp -latomic ), works fine. But when compiled as g++ -fsanitize=address -fno-omit-frame-pointer prog.cpp -latomic produces Double Free error when executed. A program based on similar lines as above has to be used in a multi-threaded application, where even the normal compilation is producing Double Free error. I read up Rule of Three/Five, which is generally referred to in case of Double Free, and various other documentations but nothing worked.

Also, removing noexcept specifier from the class A 's default constructor produces this strange error, which also I would like to know about.

error: function ‘std::atomic<_Tp>::atomic() [with _Tp = A]’ defaulted on its first declaration with an exception-specification that differs from the implicit declaration ‘std::atomic<A>::atomic()’
   atomic() noexcept = default;
   ^

Answer 1

std::atomic requires a trivially copyable type, which your A is not, because its member of type vector<int> (eg) is not trivially copy constructible.

GCC only detects a violation of that requirement since version 5.0.

The fact that older gcc versions compile the code does not mean that it is valid.