linker errors with class

Mike Parker aldacron at
Sun Oct 26 17:13:00 PDT 2008

Denis Koroskin wrote:
> On Sun, 26 Oct 2008 10:03:32 +0300, Mike Parker <aldacron at> wrote:
>> Michael P. wrote:
>>> BCS Wrote:
>>>> Reply to Michael P.,
>>>>> I'm getting an undefined reference error with Derelict and SDL.
>>>>> I tried to create an SDLImage class, but I got an error when the files
>>>>> try to link together.
>>>>> I've attached the two .d files in a rar.
>>>>> I compiled with "build imagetest".
>>>>> I have Bud 3.04, and DMD version 1.036.
>>>>> I have compiled other SDL programs, so everything is set up properly
>>>>> with Derelict.
>>>>> -Michael P.
>>>> what are the error messages? (copy/pates)
>>>  C:\Documents and Settings\Default\My Documents\DProjects\Derelict\ 
>>> build imagetest
>>> OPTLINK (R) for Win32  Release 8.00.1
>>> Copyright (C) Digital Mars 1989-2004  All rights reserved.
>>> SDLImages.obj(SDLImages)
>>> Error 42: Symbol Undefined _D9SDLImages11SDL_Imagess5_dtorMFZv
>> The linker is expecting to find a destructor for your SDLImagess class 
>> in the object file, but it's not there. Your problem is on line 44 of 
>> SDLImages.d:
>> //Destructor
>> ~this();
>> Your destructor is declared, but not implemented -- hence the error. 
>> If you've got nothing to do in the destructor, either implement an 
>> empty one:
>> ~this() {}
>> Or take it out entirely, in which case the compiler will generate a 
>> default destructor for you.
>> IMO, this should really be a compiler error. I'm surprised it isn't.
> No, it shouldn't. You may implement function bodies in other modules 
> and/or languages (in C, for example, just make sure names have proper 
> mangling).

Right, but it just feels wrong to me for constructors & destructors 
since they are a required part of the class. Either you implement one or 
you don't, but simply declaring one without an implementation feels like 
an error to me.

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