how to ignore LNK2005 & LNK1169? - c++

So I have a Visual Studio 2010 project that uses external libraries and in order to get it compile without LNK2005 I had to juggle arround with the order of the libraries in the linker settings.
I got it to compile fine in release mode, but for whatever reasons I don't manage to get it to compile without LNK errors in debug.
Is there no way to generally ignore LNK2005 and tell the linker to simply use whatever he encounters first?
Thanks!
//edit: here are some of the errors output of the PARTICULAR problem. however I already tried to solve that in different ways with each solution giving me different linker problems. hence i'm looking for general solution to ignore LNK2005
Error 7 error LNK2005: "private: __thiscall type_info::type_info(class type_info const &)" (??0type_info##AAE#ABV0##Z) already defined in Libcmtd.lib(typinfo.obj)
...\msvcprtd.lib(MSVCP100D.dll)
Error 8 error LNK2005: "private: class type_info & __thiscall type_info::operator=(class type_info const &)" (??4type_info##AAEAAV0#ABV0##Z) already defined in Libcmtd.lib(typinfo.obj)
...\msvcprtd.lib(MSVCP100D.dll)
Error 9 error LNK2005: _exit already defined in Libcmtd.lib(crt0dat.obj)
...\msvcprtd.lib(MSVCP100D.dll)
Error 10 error LNK2005: __invalid_parameter already defined in Libcmtd.lib(invarg.obj)
...\msvcprtd.lib(MSVCP100D.dll)
...
Error 37 error LNK1169: one or more multiply defined symbols found


You may try the linker-option /FORCE (Force File Output in the Linker General tab of the Project Properties). This will force the linker to create a exe/dll even when such errors occur. But its left to you to find out if this exe does work at all or even correctly. After all i would not recommend this strategy.
Linker errors can sometimes be tedious to solve, but usually it has to be done only after migrating or setting up a project. This may take quite a while - it sometimes took me more then a day, but it should be done properly.


You absolutely must not ignore linker errors, ever! A linker is telling you that it's confused about a symbol that's defined in multiple places - where should it take the definition from? Do you really want it to be arbitrary? What about when you change your code and the linker randomly decides to take the other definition which might suddenly break your code?
Instead of fighting the tool, correct your code so that it compiles and links without errors. This MSDN article has some information on fixing it, along with links for more information.

Related

Linker error building Qt 5.6 - multiply defined symbols

Trying to build Qt 5.6 from source on Windows 7 using MSVC13. Compilation goes fine, but I get two linker errors regarding multiply defined symbols:
Qt5SerialBus.lib(qmodbusdevice.obj) : error LNK2005: "class QLoggingCategory const & __cdecl QT_MODBUS(void)" (?QT_MODBUS##YAAEBVQLoggingCategory##XZ) already defined in mainwindow.obj
Qt5SerialBus.lib(qmodbusdevice.obj) : error LNK2005: "class QLoggingCategory const & __cdecl QT_MODBUS_LOW(void)" (?QT_MODBUS_LOW##YAAEBVQLoggingCategory##XZ) already defined in mainwindow.obj
release\adueditor.exe : fatal error LNK1169: one or more multiply defined symbols found
I suspect the problem (and solution) are similar to this one in which the offending functions can just be marked inline, however I can't find the definitions for these two functions anywhere in the modbus code. Does anyone know where "QT_MODBUS" and "QT_MODBUS_LOW" are defined, or is there another workaround to this?

LNK2019 unresolved external symbol after moving functions to another header file

I had two array templates in one of my header files, everything worked well. Then I thought, I'd better get some more pedantism into my code, so I moved them all into another header file, mostly just for them (and for another function, that wants to use one of them). And then I got LNK2019 error every time I used functions from these templates in other header files.
Since everything was good before I pasted my code elsewhere, I assume the code is okay, it's just my lack of understanding. Basically, the question is: why do I get a linker error when I moved my function to another header file?
Here is an example of one of my errors:
Error LNK2019 unresolved external symbol "public: char __thiscall C2DArray::Get(int,int)" (?Get#?$C2DArray#D##QAEDHH#Z) referenced in function "public: char __thiscall SGame::GetRecordOutput(int,int)" (?GetRecordOutput#SGame##QAEDHH#Z) Mastermind C:\Users\Master\Documents\Visual Studio 2015\Projects\Mastermind\Mastermind\Menu.obj 1
I'm using Visual Studio 2015 if it matters.

Thank you for the reply. As it seems, I have resolved my problem. The cause was the class templats, which were not specialized (and had to be). All I had to do is include what types of these templates I wanted. Sorry for posting before doing more extensive research.

Linking error: LNK2019 & LNK1120

First I had some OpenCL code and when I put it away in another function, I got this error, then I thought maybe its something with OpenCL, but now even my every normal code suddenly appears to report this error whenever I make new function and put main function code in those functions. I have rechecked that prototypes, functions calls and function definitions are exactly same and matches, also since I have this problem with those functions in which there are more arguments like upto 8 or 10 but I read that C/C++ functions supports more 50 or so arguments passing. The error information is:
ImgConv.obj : error LNK2019: unresolved external symbol "void __cdecl function(.............) (?conv_ser##YAXPBMPAM10HHH#Z) referenced in function _main
fatal error LNK1120: unresolved externals
I am reporting error that has lot of forum entries and solution information such as linking some library function or functions prototyping mistakes etc, I have read them but there is non related to my problem.

Check the linker input settings in your project configuration and make sure that the appropriate libraries are included (or add them to the project itself). Visual Studio doesn't do this automatically just because you add the source code to your project.
If 'conv_ser' is a function that you created make sure that the implementation for that function is available in the project. Double check to make sure that the arguments in the prototype (typically in the header) match that of the any implementation you have added.

Have you tried deleting all instances of void __cdecl function? Just search through your project and comment it out. See if your code will compile after this.

Linker Errors due to being Already Defined

It has been about a year since I wrote any .dll plugins that use LibCurl, but I decided to start on another one tonight. Unfortunately, I have been combating the same linker errors for almost 4 hours now, and I am completely lost.
I am statically building LibCurl, and it appears to be fine for the most part, except I am getting the following linker errors.
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: _calloc already defined in memoverride.obj
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: _realloc already defined in memoverride.obj
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: _free already defined in memoverride.obj
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: _malloc already defined in memoverride.obj
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: __strdup already defined in memoverride.obj
1>MSVCRT.lib(MSVCR90.dll) : error LNK2005: __malloc_crt already defined in memoverride.obj
I have tried...
1) Reorganizing my included libs due to MSDN saying LNK2005 was caused by this.
2) Rebuilding the LibCurl lib through MSVC Application, then through the Command-Line tool.
3) Excluding the libs that are causing issues.
and a bunch of other things that I cannot even remember now. Can anyone help me out with some information as to how I can solve these?

Problem was my .dll was /MT while the libcurl was /MD. Also, I had initially blocked "libcmt", so when I was switching libcurl to /MT, it was spewing errors.

MSVS2010 linker error sadness - not entirely sure what is wrong

I am using a library of code from a tutorial for providing functionality for passing function points of non-static member functions to a function that expects a static function pointer, probably helps to know what I am suing, so here is the link http://www.codeproject.com/KB/cpp/thunk32.aspx This code uses the Boost library, which I have downloaded and set-up more or less everything from.
In the Thunk library, one of the header files has a section that reads
#define BOOST_PP_ITERATION_PARAMS_1 (3,(0,THUNK32_MAX_ARGS,"Thunk32_template.h"))
??=include BOOST_PP_ITERATE()
#undef BOOST_PP_ITERATION_PARAMS_1
but this gives me epic amounts of errors, which I can solve by changing it to
#define BOOST_PP_ITERATION_PARAMS_1 (3,(0,THUNK32_MAX_ARGS,"Thunk32_template.h"))
#include BOOST_PP_ITERATE()
#undef BOOST_PP_ITERATION_PARAMS_1
This code that is downloaded is included in my solution as a second project, which is able to compile and build happily. But my project that is using this code has issues linking, to save people asking, I get these error messages
1>WebCamera.obj : error LNK2019: unresolved external symbol "protected: __thiscall indev::Thunk32Base::Thunk32Base(void)" (??0Thunk32Base#indev##IAE#XZ) referenced in function "public: __thiscall indev::Thunk32<class WebCamera,void __cdecl(struct HWND__ *,struct videohdr_tag *)>::Thunk32<class WebCamera,void __cdecl(struct HWND__ *,struct videohdr_tag *)>(void)" (??0?$Thunk32#VWebCamera##$$A6AXPAUHWND__##PAUvideohdr_tag###Z#indev##QAE#XZ)
1>WebCamera.obj : error LNK2019: unresolved external symbol "protected: __thiscall indev::Thunk32Base::~Thunk32Base(void)" (??1Thunk32Base#indev##IAE#XZ) referenced in function "public: __thiscall indev::Thunk32<class WebCamera,void __cdecl(struct HWND__ *,struct videohdr_tag *)>::~Thunk32<class WebCamera,void __cdecl(struct HWND__ *,struct videohdr_tag *)>(void)" (??1?$Thunk32#VWebCamera##$$A6AXPAUHWND__##PAUvideohdr_tag###Z#indev##QAE#XZ)
1>WebCamera.obj : error LNK2019: unresolved external symbol _capCreateCaptureWindowA#32 referenced in function "public: bool __thiscall WebCamera::Init(struct HWND__ *)" (?Init#WebCamera##QAE_NPAUHWND__###Z)
I think this is trying to say that the constructor and destructor are not declared and that my WebCamera.Init()is messed up as well. I have made sure that the library that the Thunk32 project exports is included in my other project, but still I get these errors.
I would like to know if I have made the correct assumption that ??=include should have been changed to #include and if I have, what have I done wrong or failed to do that results in these linker errors. Or if you can provide me with a different way of being able to pass a function pointer to a non-static member function that would be awesome.
Thanks

??= is a "trigraph" sequence for the # character. according to the standard, trigraphs are supposed to be handled as one of the first steps in processing (in phase 1 - before the preprocessor handles directives),so:
??=include "whatever"
Should be equivalent to:
#include "whatever"
so you should be able to use that form (I wonder why the trigraph was put there in the first place - some sort of evil joke perhaps?)
However, trigraphs cause problems and confusion (probably more than they help), so compilers seem to be moving towards warning about them and/or defaulting to not handling them. The compiler in VS 2010 has trigraph processing turned off by default - you have to use the /Zc:trigraphs option to turn it on.
See Purpose of Trigraph sequences in C++? for more details.

Ah, Einar, good man. Doing flash and Sharepoint stuff these days, ouch. Norwegian, might explain the trigraphs.
Anyhoo, nothing complicated, you just forgot to tell the linker to look at some libraries. Right-click your project, Project Dependencies, tick the Thunk project. That makes sure that Thunk32.lib gets looked at and resolves the ctor and dtor.
Right-click again, Properties, Linker, Additional dependencies, add "winmm.lib". That resolves the capCreateCaptureWindow symbol.

Do you have a constructor and a destructor declared in the indev::Thunk32Base class that you forgot to define in its cpp file?

Ok, so I have managed to solve this now.
Michael Burr nicley said that ??= is basically the same as typing # but in a way that people who dont have the hash symbol can type it, see Purpose of Trigraph sequences in C++?
Hans Passant then got the ball rolling for me buy letting me know that I had not fully linked in stuff. I needed to right click on my main project, select 'Project Dependencies' and select my other project that has the thunk32 code. I also needed to tell my main project to look at where the Thunk project is saving the lib, which turned out to be in a folder in my documents (explain that one!). I also needed to add the Thunk32d.lib (note the 'd' because I was/am in debug mode. Hans said that I needed winmm.lib but it turned out (when googling the function that was giving me the error that I needed Vfw32.lib instead.
Thanks guys! I hope that by giving the full answer like this it can help some one else who has a similar problem.