I created a default ATL project with MSVC 2010 with a simple default ATL dialog. Then I added the second project into solution, named MyControls, where I created ATL DHTML Control with a help of Wizard. Then I placed ATL DHTML Control to ATL dialog.
Now I would like to call some methods of that ATL DHTML Control in ATL dialog's OnInitDialog function. In order to be able to make a call like:
CComPtr<IDHTMLControl> ptr;
HRESULT hr = GetDlgControl(IDC_ACTIVEX_CONTROL_DHTML
, IID_IDHTMLControl, (void**)&ptr);
I am including the file DHTMLControl.h from MyControls project. However, I get the following errors:
Error 1 error LNK2001: unresolved external symbol _IID_IDHTMLControl
Error 2 error LNK2001: unresolved external symbol _LIBID_MyControlsLib
Error 3 error LNK2001: unresolved external symbol _CLSID_DHTMLControl
Error 4 error LNK2001: unresolved external symbol _IID_IDHTMLControlUI
Note: It appears that I am linking MyControls.lib incorrectly, however, I added MyControls.lib to Linker->Input->Additonal Dependencies & specified ../$(Configuration) in the Linker->General->Additional Library Directories.
Anyone have an idea?
Thanks!
The problem is related to how you link one project with the other. There is something missing here and since you don't show the code, it's a pure guess only.
On control project you have a type library which, when being built, also generates files MyControls_i.h, MyControls_i.c, MyControls_p.c. I suppose that on the application project you included _i.h file which declared symbols as externals, and you did not include the _i.c file with symbols actually defined.
Related
I'm trying to use ffmpeg libraries in a VC++ project. I added all the lib files and the headers and set up the properties for the compiler/linker including the .def file for the externals. All the libs/headers/defs come directly from ffmpeg windows 64bit builds. After all that I get errors like:
1>exports.def : error LNK2001: unresolved external symbol pp_help
1>exports.def : error LNK2001: unresolved external symbol swr_ffversion
1>exports.def : error LNK2001: unresolved external symbol sws_context_class
All of the definitions that are failing have a DATA keyword following them.
There are a total of 37 of them and all have the DATA keyword....
I'm new to the VS Compiler/Linker and I might have simply missed something. Any pointers would be greatly appreciated.
Why you define them in exports? You need to use exports.def only when you export something link. For ex. if you develop your own library.
Here you don't need to specify it in exports. You need to correctly link the lib and include headers.
The errors appear, because linker can't find the exported functions definitions. It thinks that you have declared and implemented those functions somewhere.
We have a project which is an executable, which loads DLL files at run time as plugins.
We're trying to make a new plug in which has many library dependencies, and some of those dependencies are the same library but different versions that other plugins link to.
Because the libraries are depended on by different plugins at different versions, I would like to statically link/build any dependencies into the new plugin - that way they can't conflict with the old plugin dependencies. As far as I know, nothing in the dependencies of the plugin need to be exported, they're just used by the plugin.
Is it possible to do this?
I've tried building all the static libs in visual studio as static libraries with the runtime set to Multithreaded DLL with the /MD flag, but when I try to build dynamiclibB.dll, I get linker errors. If I set dynamiclibB to build as a static library, it doesn't have the linker errors.
I haven't tried linking newplugin.dll to the static library version of dynamiclibB yet, but I think I have exactly the same situation, so I see no reason why it would work there where it doesn't one level down.
I don't want to build dynamiclibB as a static library anyway, as it would be good to be able to update newplugin.dll without including dynamiclibB.dll if it hasn't been changed, as in, to decouple the update process. This line of reasoning would suggest that I should have .dlls for everything, but the conflicts of versions is what worries me, I think.
I cannot build the plugins as static libraries as they need to be loaded at run time.
Absolutely everything is being built in release mode for now, to avoid that complication.
What am I missing?
An attempt at a diagram that might help understand the situation:
program.exe
|
________________
| |
oldplugin.dll newplugin.dll
| |
dynamiclibA.dll dynamiclibB.dll
|
_________________________
| | |
staticlibA.lib slibC.lib slibD.lib
Update:
Providing some more information now that I know what's happening, and know that more specific details are actually relevant.
So library A, represented by dynamiclibA and staticlibA was zlib.
The library we were compiling (dynamiclibB) for use in the newplugin was PoDoFo.
The error messages we got were:
Error 19 error LNK2001: unresolved external symbol
_deflateInit_ E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 20 error LNK2001: unresolved external symbol
_inflateEnd E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 21 error LNK2001: unresolved external symbol
_inflateEnd E:\Work\podofo_bin\src\libpng16.lib(pngread.obj) podofo_shared Error 22 error LNK2001: unresolved external symbol
_deflate E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 23 error LNK2001: unresolved external symbol
_deflate E:\Work\podofo_bin\src\libpng16.lib(pngwutil.obj) podofo_shared Error 24 error LNK2001: unresolved external symbol
_deflateEnd E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 25 error LNK2001: unresolved external symbol
_deflateEnd E:\Work\podofo_bin\src\libpng16.lib(pngwrite.obj) podofo_shared Error 26 error LNK2001: unresolved external symbol
_inflateInit_ E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 27 error LNK2001: unresolved external symbol
_inflateInit_ E:\Work\podofo_bin\src\libpng16.lib(pngrutil.obj) podofo_shared Error 28 error LNK2001: unresolved external symbol
_inflate E:\Work\podofo_bin\src\PdfFiltersPrivate.obj podofo_shared Error 29 error LNK2001: unresolved external symbol
_inflate E:\Work\podofo_bin\src\libpng16.lib(pngrutil.obj) podofo_shared
Putting the rest in an answer.
In my question, slibc.lib was libpng. Libpng also requires zlib, but it builds it from source inside its solution. We were able to use the output of that project in the way we desired, as in, zlib.lib built with /MD flag, without linking errors.
We've also managed to work out why this problem occurred:
another stackoverflow question was very relevant: https://stackoverflow.com/a/6559315/78823
Turns out that zlib has a #define ZLIB_WINAPI which defined the call convention to be STDCALL, which I don't understand, but it caused the linker errors. The other answer suggests to remove the define, and I suppose that's what libpng did with its zlib project.
I'm guessing that the reason why the linker errors only occurred when building the .dll and disappeared when building the .lib is because (correct me if I'm wrong, I don't fully understand this), build a .lib doesn't actually do the linking to the required functions, so would have been just passing on the linker errors to the next level up; I think we would have seen the same errors (but in different objs/projects perhaps) when compiling newplugin.dll, but we didn't get far enough to check that before we tried other things.
I am facing issues with the C++ cUrl Library on Windows, using Visual Studio 2012.
I have a CGI project which generates a .cgi file. This project includes another project called Library which is a Static Library Project.
In the Library project, I have the code which uses cUrl and includes curl/curl.h. I have referenced the Preprocessor Definition CURL_STATICLIB.
Then in my CGI Project, I have linked libcurl.lib to my project in Configuration Properties > Linker > Additional Dependencies.
But when I try to build the Solution, I still have those errors :
error LNK2001: unresolved external symbol _curl_easy_setopt in Library.lib(fct_util.obj)
error LNK2001: unresolved external symbol _curl_easy_perform in Library.lib(fct_util.obj)
error LNK2001: unresolved external symbol _curl_easy_init in Library.lib(fct_util.obj)
error LNK2001: unresolved external symbol _curl_easy_cleanup in Library.lib(fct_util.obj)
I already took a look at this topic : Unresolved symbols when linking a program using libcurl, as well as other related topics but couldn't find a solution for my problem.
Am I missing something ?
Kind Regards.
Credit to this guy helped me get further than any docs.
Still have a couple more issues.
https://www.youtube.com/watch?v=wjNyT5PhNvI
Then do this , someone in the video comments
Very important after you do everything in video.
Need to navigate back to solution right click properties
(see below comment)
"Thanks , it worked after i added Normaliz.lib;Ws2_32.lib;Wldap32.lib;Crypt32.lib;advapi32.lib in Additional Dependencies(property->linker->input)"
This is my situation (I am very new to C++ MFC coding and I am trying to debug an existing application project)
I use this line in my code (in a visual studio 2012 MFC project)
CoCreateInstance(CLSID_PortableDeviceValues, NULL,
CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&x));
While I run the project, i get a linker error like this
error LNK2001: unresolved external symbol _CLSID_PortableDeviceValues
This happens for all the CLSID values that I am referring to in the code. Like this
error LNK2001: unresolved external symbol
_CLSID_PortableDeviceKeyCollection
error LNK2001: unresolved external symbol _IID_IPortableDeviceEventCallback
error LNK2001: unresolved external symbol _CLSID_PortableDeviceManager
error LNK2001: unresolved external symbol _CLSID_PortableDeviceServiceFTM
I checked for the declaration of "CLSID_PortableDeviceValues" and it was found in "PortableDeviceTypes.h" and I have imported that library as well.
I do not get any compiler error, but run into the linker errors mentioned above..
Can someone please help me out here. I could not resolve this ..
You will need to add PortableDeviceGUIDs.lib to your project.
(Look up the section "Requirements" in the MSDN documentation for IPortableDeviceValues)
When the linker builds your project, it is looking for the implementation data that is behind the identifier CLSID_PortableDeviceValues. This data is in the library PortableDeviceGUIDs.lib, and the linker has to be told to use this library.
The header file you included in your source code only declares the symbol "CLSID_PortableDeviceValues", without importing its implementation.
I just tried to build Qt for WinCE7.0 using VS2008 after lots of code modification I successfully compiled main libraries.
While Compiling the QtScript library I received the following linker errors:
1>Linking...
1> Creating library ..\..\lib\QtScript4.lib and object ..\..\lib\QtScript4.exp
1>BytecodeGenerator.obj : error LNK2019: unresolved external symbol __imp__Inf referenced in function "public: static double __cdecl QTWTF::FloatHashTraits<double>::emptyValue(void)" (?emptyValue#?$FloatHashTraits#N#QTWTF##SANXZ)
1>Executable.obj : error LNK2001: unresolved external symbol __imp__Inf
1>MathObject.obj : error LNK2001: unresolved external symbol __imp__Inf
1>DateMath.obj : error LNK2019: unresolved external symbol __imp__Nan referenced in function "double __cdecl QTWTF::parseDateFromNullTerminatedCharacters(char const *,bool &,int &)" (?parseDateFromNullTerminatedCharacters#QTWTF##YANPBDAA_NAAH#Z)
1>JSValue.obj : error LNK2001: unresolved external symbol __imp__Nan
1>..\..\lib\QtScript4.dll : fatal error LNK1120: 2 unresolved externals
I have absolutely no idea which libraries I missed to link with!
Thanks
If you're using Windows, I'll assume you're building in MSVS. I often start projects WITHOUT default libs and if I happen to touch "out of reach" terriotry from another lib, I add what I need as I go along.
Fortunately, MSVS is great at helping me with this. Just turn VERBOSE compiling status and see what libs it's trying to access, then just add them:
right click the project, linker, show progress -> select VERBOSE
Another method is when I check MSDN for Microsoft functions and see the lib they are declared in and add it (since VERBOSE can be overkill on my poor output window). I don't know if Qt has a detailed reference documentation (also stating the libs) but it's worth a shot.
When all else fails, just add all libs Qt could possibly want (make sure IGNORE STANDARD LIBS is disabled) then check VERBOSE and only keep those in the list.
Assuming you have all the libraries in the project, another problem is mismatched dependencies (right click the solution, startup project -> select the one you need, [project dependencies -> map each dependency for the specified libs).
Also make sure when you import an extern the lib is defined in Linker->Input.
However, if you modified the source (either adding new functions/global or static vars or you modified function signatures), the unresolved external reference means a function/var definition has no associated body. Either implement one or add { } in the definition; so if that's the case, check the functions/vars from the error message.