Argthtjtr

Each of these files should be in the same directory, and can be copied verbatim. I'm having a very odd property access issue which I don't understand with what I currently know about C++.

main.cpp

#include "someclass.hpp"



SomeClass d = SomeClass();



int main(int argc, const char * argv)

{

    SomeClass c = SomeClass();



    return 0;

}

someclass.hpp

#ifndef someclass_hpp

#define someclass_hpp



class SomeClass

{

public:

    SomeClass();

};



#endif /* someclass_hpp */

someclass.cpp

#include "someclass.hpp"

#include <iostream>



std::string s = "hi";



SomeClass::SomeClass()

{

    std::cout << """ + s + """ << std::endl;

}

console

$ g++ main.cpp someclass.hpp someclass.cpp 

$ ./a.out

""

"hi"

I've taken a fairly large project and removed everything until I'm left with this very simple bug, which I've been staring at for an hour and can't wrap my head around. Is this a simple problem that I'm not thinking about the right way? As far as I can tell, the code should output "hi" twice, what makes the context of the initialization of a any different from b?

I currently have the solution down to "don't init variables outside of methods", but I'm still curious why this occurs.

Keep in mind that both, std::string s = "hi"; and SomeClass d =
SomeClass(); are initialized globally and the order of initialization isn't
guaranteed. This can also lead to undefined behavior.

FYI: your example is crashed on the latest Fedora.

UPD As @davidbak correctly mentioned, my answer is about the order of global initialization in different compilation units.

Global variable initialization has no guarantee of order. Since the std::string s = "hi"; and SomeClass d = SomeClass(); are both in global scope, when your SomeClass d is created, string s is not initialized, hence the "" output. As dshil correctly pointed out, this would result undefined behaviour and should be avoided.