Thread: Dynamic Library, Header Files Visibility.

Hello!

I'm creating a game engine using the SDL library and i stepped into a problem.

Say i have this definition:

SMengine.h

Code:

#include <SDL.h>

namespace SMengine
{
    class Init
    {
        private:
            SDL_Window *w;

        public:
            __declspec(dllexport) Init();
            __declspec(dllexport) ~Init();
    };
}

And after compiling the above code to a dll library i want the end user to be able to use it without seeing the #include <SDL.h>
definitions.

End user's code:

Code:

#include <SMengine.h>

int main()
{
    //do what you have to do.
}

SMengine.h includes SDL.h so the end user also includes SDL.h .

The end user needs SDL.h in order to compile his code but he doesn't need to know what's in there.

He should only be able to see the SMengine class, the Constructor and the Deconstructor.

So is there a way to hide the definitions of SDL.h from the end user?

Thank you!

I am not a C++ programmer; but, I think you can hide includes inside of namespaces.

Tim S.

Originally Posted by stahta01

I am not a C++ programmer; but, I think you can hide includes inside of namespaces.

Tim S.

Well i tried it but i get a bunch of weird errors when i compile it.

SMengine.h

Code:

#pragma once




namespace myspace
{
#include <iostream>
#include <SDL.h>
}


class SMengine
{


public:
    __declspec(dllexport) SMengine();
    __declspec(dllexport) ~SMengine();


};

SMengine.cpp

Code:

#include "SMengine.h"






SMengine::SMengine()
{
    if (myspace::SDL_Init(SDL_INIT_EVERYTHING) < 0)
        myspace::std::cout << "Something went wrong" << myspace::std::endl;


    else
        myspace::std::cout << "Its time to roll!!!" << myspace::std::endl;


    myspace::std::cin.get();
}




SMengine::~SMengine()
{
}

Errors In Visual Studio:

Code:

1>------ Build started: Project: SMengine, Configuration: Debug Win32 ------
1>SMengine.cpp
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(20): error C2039: 'fabs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(25): error C2039: 'fabsf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(30): error C2039: 'fabsl': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(34): error C2039: 'div_t': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(34): error C2873: 'div_t': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(34): error C2039: 'ldiv_t': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(34): error C2873: 'ldiv_t': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(35): error C2039: 'abort': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(35): error C2873: 'abort': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(35): error C2039: 'abs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(35): error C2873: 'abs': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2039: 'atof': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2873: 'atof': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2039: 'atoi': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2873: 'atoi': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2039: 'atol': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(36): error C2873: 'atol': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2039: 'bsearch': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2873: 'bsearch': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2039: 'calloc': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2873: 'calloc': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2039: 'div': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(37): error C2873: 'div': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(38): error C2039: 'exit': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(38): error C2873: 'exit': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(38): error C2039: 'free': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(38): error C2873: 'free': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2039: 'labs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2873: 'labs': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2039: 'ldiv': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2873: 'ldiv': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2039: 'malloc': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(39): error C2873: 'malloc': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2039: 'mblen': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2873: 'mblen': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2039: 'mbstowcs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2873: 'mbstowcs': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2039: 'mbtowc': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(40): error C2873: 'mbtowc': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2039: 'qsort': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2873: 'qsort': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2039: 'rand': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2873: 'rand': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2039: 'realloc': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(41): error C2873: 'realloc': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2039: 'srand': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2873: 'srand': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2039: 'strtod': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2873: 'strtod': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2039: 'strtol': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(42): error C2873: 'strtol': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(43): error C2039: 'strtoul': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(43): error C2873: 'strtoul': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(44): error C2039: 'wcstombs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(44): error C2873: 'wcstombs': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(44): error C2039: 'wctomb': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(44): error C2873: 'wctomb': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(46): error C2039: 'lldiv_t': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(46): error C2873: 'lldiv_t': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(49): error C2039: 'getenv': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(49): error C2873: 'getenv': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(50): error C2039: 'system': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(50): error C2873: 'system': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2039: 'atoll': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2873: 'atoll': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2039: 'llabs': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2873: 'llabs': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2039: 'lldiv': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(53): error C2873: 'lldiv': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(54): error C2039: 'strtof': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(54): error C2873: 'strtof': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(54): error C2039: 'strtold': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(54): error C2873: 'strtold': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(55): error C2039: 'strtoll': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(55): error C2873: 'strtoll': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(55): error C2039: 'strtoull': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(55): error C2873: 'strtoull': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2039: '_Exit': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2873: '_Exit': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2039: 'at_quick_exit': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2873: 'at_quick_exit': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2039: 'quick_exit': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cstdlib(57): error C2873: 'quick_exit': symbol cannot be used in a using-declaration
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(20): error C2039: 'pow': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(25): error C2039: 'acosf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(30): error C2039: 'acoshf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(35): error C2039: 'asinf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(40): error C2039: 'asinhf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(45): error C2039: 'atanf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(50): error C2039: 'atanhf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(55): error C2039: 'atan2f': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(60): error C2039: 'cbrtf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(65): error C2039: 'ceilf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(71): error C2039: 'copysignf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(76): error C2039: 'cosf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(81): error C2039: 'coshf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(86): error C2039: 'erff': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(91): error C2039: 'erfcf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(96): error C2039: 'expf': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(101): error C2039: 'exp2f': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(106): error C2039: 'expm1f': is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.12.25827\include\cmath(106): fatal error C1003: error count exceeds 100; stopping compilation
1>Done building project "SMengine.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

This is so weird. These symbols at the errors are from the math.h library, how does this make sense

Why did you try to hide iostream header?

Originally Posted by babaliaris

So is there a way to hide the definitions of SDL.h from the end user?

Yes, by using the pimpl (pointer to implementation) idiom. That is, instead of declaring the SDL_Window member in the SMengine::Init class, you will do so in another class that exists purely to implement the SMengine::Init class. The SMengine::Init class will then have a pointer to an object of this implementation class through which it will implement all its member functions. Hence, the <SDL.h> header will only be included in your source file that contains the definition of the implementation class and its implementation. The user of SMengine::Init include a header that has no trace of SDL, although it will have a forward declaration of the implementation class as well as the definition of the SMengine::Init class.

You should not try to "hide includes inside of namespaces": it doesn't hide anything.

Originally Posted by babaliaris

I think i got it.

Also i noticed this:

Before i do this, the client had to link with the SDL Library and SMengine in order to compile his code but now he doesn't need to do that. Once the SMengine library is compiled (and linked with SDL) he just have to compile his code only by linking with the SMengine. I don't really understand that. Is it because when the client was including SDL from SMengine he had to link with SDL because he was including source code from SDL?

The SDL library breaks a few rules; including requiring the main function signature to be just right. IIRC, it replaces the main function in some use cases.

Tim S.

Originally Posted by babaliaris

Before i do this, the client had to link with the SDL Library and SMengine in order to compile his code but now he doesn't need to do that. Once the SMengine library is compiled (and linked with SDL) he just have to compile his code only by linking with the SMengine. I don't really understand that. Is it because when the client was including SDL from SMengine he had to link with SDL because he was including source code from SDL?

Yes, the pimpl idiom is intended for these scenarios where you want to have the flexibility of changing the implementation without requiring users of your library (in this case SDL, even though it isn't yours per se) to recompile, with the tradeoff of some overhead (e.g., the compiler cannot inline those "extra" function calls that are made to call the implementation functions).