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What is an undefined reference/unresolved external symbol error and how do I fix it?
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Closed 5 years ago.
I am trying to build a C++ program and keep on getting LNK2019 link errors whenever I try defining a new function and building it. I resolved few of them till now, but spend a lot of time to understand the error in detail. Errors I am getting now are as per below:
Error 22 error LNK2019: unresolved external symbol "public: __thiscall xmlElements::operator class std::basic_string,class std::allocator >(void)" (??BxmlElements##QAE?AV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##XZ) referenced in function "public: class xmlTags & __thiscall xmlTags::addSib(class xmlElements)" (?addSib#xmlTags##QAEAAV1#VxmlElements###Z)
Error 25 error LNK2019: unresolved external symbol "public: __thiscall xmlElements::operator class std::basic_string,class std::allocator >(void)" (??BxmlElements##QAE?AV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##XZ) referenced in function "public: class xmlTags & __thiscall xmlTags::addSib(class xmlElements)" (?addSib#xmlTags##QAEAAV1#VxmlElements###Z)
Error 23 error LNK2019: unresolved external symbol "public: __thiscall xmlTags::xmlTags(void)" (??0xmlTags##QAE#XZ) referenced in function "public: static void __cdecl xmlTags::makeDoc(void)" (?makeDoc#xmlTags##SAXXZ)
Error 26 error LNK2019: unresolved external symbol "public: __thiscall xmlTags::xmlTags(void)" (??0xmlTags##QAE#XZ) referenced in function "public: static void __cdecl xmlTags::makeDoc(void)" (?makeDoc#xmlTags##SAXXZ)
Going through various forums I understood that I need to add some library name and its path, but I am bad at library thing. From where can I get its name and the path?
To use a library:
go under Project/<projectname>Properties/Configuration Properties/CC++/Additional Include Directories and enter in the directory where the header files for the library are.
Then also under Configuration Properties/Linker/General/Additional Library Directories enter in the location of the lib directory.
Then under Configuration Properties/Linker/Input/Additional dependencies put the name(s) of the lib files in the lib directory.
Related
I'm trying to code a program that can edit mp3 tag.
And now,I have a problem.
That is,when I compile,there is always errors.
and the error is Linker error.
Here is error descriptions:
error LNK2019: unresolved external symbol "__declspec(dllimport) public: __thiscall ID3_Tag::ID3_Tag(char const *)" (__imp_??0ID3_Tag##QAE#PBD#Z) referenced in function _wmain
error LNK2019: unresolved external symbol "__declspec(dllimport) public: virtual __thiscall ID3_Tag::~ID3_Tag(void)" (__imp_??1ID3_Tag##UAE#XZ) referenced in function _wmain
Does anyone know how or what to do??
You probably didn't link against the appropriate libraries, where the symbols the linker is complaining about are exported.
Here's how to link against the libs which are probably found in this archive (version number subject to change).
Since SCons has been deprecated. I used the gyp to generate vs solution.
I did what they told me on the build BuildingWithGYP.
And the v8 project builded ok!
and I got the v8_base.lib but no v8.lib.
And in the hello world project ,get started.I add the lib directory into the add library.
But it linked failed:
Linking...
1>v8test.obj : error LNK2019: unresolved external symbol "public:
__thiscall v8::HandleScope::~HandleScope(void)" (??
1HandleScope#v8##QAE#XZ) referenced in function _main
1>v8test.obj : error LNK2019: unresolved external symbol "public:
__thiscall v8::String::AsciiValue::~AsciiValue(void)" (??
1AsciiValue#String#v8##QAE#XZ) referenced in function _main
1>v8test.obj : error LNK2019: unresolved external symbol "public:
__thiscall v8::String::AsciiValue::AsciiValue(class v8::Handle<class
v8::Value>)" (??0AsciiValue#String#v8##QAE#V?$Handle#VValue#v8###2##Z)
referenced in function _main
1>v8test.obj : error LNK2019: unresolved external symbol "public:
class v8::Local<class v8::Value> __thiscall v8::Script::Run(void)" (?
Run#Script#v8##QAE?AV?$Local#VValue#v8###2#XZ) referenced in function
_main
……
It seems that couldn't find the implement
but i used the dumpbin tool and find the symbol i can find them in the v8_base.lib
I am sure that the library directory is ok!
but i don't know why it couldn't find the implement.
You can add the lib "v8_base.lib" as an additional dependency to fix the problem.
I am working on a DirectX 11 project for school and I followed the book thoroughly when doing this. I keep thinking that maybe something is labeled wrong but I double checked all my files, all my class names are fine (I believe they are fine) and double checked how all my header files are setup and everything should be okay and I still get this error output:
1>BlankDemo.obj : error LNK2019: unresolved external symbol "public: __thiscall DemoBase::DemoBase(void)" (??0DemoBase##QAE#XZ) referenced in function "public: __thiscall BlankDemo::BlankDemo(void)" (??0BlankDemo##QAE#XZ)
1>BlankDemo.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall DemoBase::~DemoBase(void)" (??1DemoBase##UAE#XZ) referenced in function "public: virtual __thiscall BlankDemo::~BlankDemo(void)" (??1BlankDemo##UAE#XZ)
1>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall DemoBase::Shutdown(void)" (?Shutdown#DemoBase##QAEXXZ) referenced in function _wWinMain#16
1>main.obj : error LNK2019: unresolved external symbol "public: bool __thiscall DemoBase::Initialize(struct HINSTANCE__ *,struct HWND__ *)" (?Initialize#DemoBase##QAE_NPAUHINSTANCE__##PAUHWND__###Z) referenced in function _wWinMain#16
1>C:\Users\vaughn\documents\visual studio 2010\Projects\BlankWindow\Debug\BlankWindow.exe : fatal error LNK1120: 4 unresolved externals
How do I solve this?
Evidently, you either haven't implemented a handful of methods from the DemoBase class (including its constructor and destructor), or you haven't included the implementation file in the list of files to compile or link with your program. Implement them, and then make sure you've included the source file in your project.
I am coming from Xcode, trying to compile a project in Visual Studio 2010, and I get the following errors:
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "struct _GUID __cdecl CLEyeGetCameraUUID(int)" (?CLEyeGetCameraUUID##YA?AU_GUID##H#Z) referenced in function "public: static int __cdecl ofxCLeye::listDevices(void)" (?listDevices#ofxCLeye##SAHXZ)
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "int __cdecl CLEyeGetCameraCount(void)" (?CLEyeGetCameraCount##YAHXZ) referenced in function "public: static int __cdecl ofxCLeye::listDevices(void)" (?listDevices#ofxCLeye##SAHXZ)
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "bool __cdecl CLEyeCameraGetFrameDimensions(void *,int &,int &)" (?CLEyeCameraGetFrameDimensions##YA_NPAXAAH1#Z) referenced in function "public: void __thiscall ofxCLeye::grabFrame(void)" (?grabFrame#ofxCLeye##QAEXXZ)
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "bool __cdecl CLEyeCameraGetFrame(void *,unsigned char *,int)" (?CLEyeCameraGetFrame##YA_NPAXPAEH#Z) referenced in function "public: void __thiscall ofxCLeye::grabFrame(void)" (?grabFrame#ofxCLeye##QAEXXZ)
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "bool __cdecl CLEyeDestroyCamera(void *)" (?CLEyeDestroyCamera##YA_NPAX#Z) referenced in function "public: virtual void __thiscall ofxCLeye::close(void)" (?close#ofxCLeye##UAEXXZ)
2>ofxCLeye.obj : error LNK2019: unresolved external symbol "bool __cdecl CLEyeCameraStop(void *)" (?CLEyeCameraStop##YA_NPAX#Z) referenced in function "public: virtual void __thiscall ofxCLeye::close(void)" (?close#ofxCLeye##UAEXXZ)
... etc etc...
2>bin\clEye_debug.exe : fatal error LNK1120: 10 unresolved externals
I imagine that the compiler is trying to link CLEyeMulticam.lib but not finding it. I think that I have configured it properly.
Could you point me with the needed steps to include a library in VS2010 ?
Thank you,
marc
Apologies if this is overly pedantic. If this is a pre-built library (not built as part of the project/solution) then make sure you
a) #include the correct header
b) #define any requisite macros
c) speciy additional .lib dependencies as shown below.
You will need to specify a fully qualifed path (d:\src\project\libs\camera.lib) unless the libary file is in the LIB environment variable.
In the Property Pages for your project, navigate to Configuration > Linker > Input and add the lib file to the Additional Dependencies setting. This applies to VC++ 2008, probably likewise to 2010.
I am creating an torrent application using libtorrent in VS 2008. I tried the example given in the link http://www.rasterbar.com/products/libtorrent/examples.html
BUt it is showing me these error....how to solve them?
Linking...
main.obj : error LNK2019: unresolved external symbol "public: __thiscall libtorrent::torrent_info::~torrent_info(void)" (??1torrent_info#libtorrent##QAE#XZ) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "public: __thiscall libtorrent::torrent_info::torrent_info(struct libtorrent::lazy_entry const &)" (??0torrent_info#libtorrent##QAE#ABUlazy_entry#1##Z) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "class std::basic_ostream > & __cdecl libtorrent::operator<<(class std::basic_ostream > &,struct libtorrent::lazy_entry const &)" (??6libtorrent##YAAAV?$basic_ostream#DU?$char_traits#D#std###std##AAV12#ABUlazy_entry#0##Z) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "int __cdecl libtorrent::lazy_bdecode(char const *,char const *,struct libtorrent::lazy_entry &,int)" (?lazy_bdecode#libtorrent##YAHPBD0AAUlazy_entry#1#H#Z) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "public: void __thiscall libtorrent::lazy_entry::clear(void)" (?clear#lazy_entry#libtorrent##QAEXXZ) referenced in function "public: __thiscall libtorrent::lazy_entry::~lazy_entry(void)" (??1lazy_entry#libtorrent##QAE#XZ)
main.obj : error LNK2019: unresolved external symbol "void __cdecl libtorrent::to_hex(char const *,int,char *)" (?to_hex#libtorrent##YAXPBDHPAD#Z) referenced in function "class std::basic_ostream > & __cdecl libtorrent::operator<<(class std::basic_ostream > &,class libtorrent::big_number const &)" (??6libtorrent##YAAAV?$basic_ostream#DU?$char_traits#D#std###std##AAV12#ABVbig_number#0##Z)
main.obj : error LNK2019: unresolved external symbol "public: struct libtorrent::peer_request __thiscall libtorrent::file_storage::map_file(int,__int64,int)const " (?map_file#file_storage#libtorrent##QBE?AUpeer_request#2#H_JH#Z) referenced in function "public: struct libtorrent::peer_request __thiscall libtorrent::torrent_info::map_file(int,__int64,int)const " (?map_file#torrent_info#libtorrent##QBE?AUpeer_request#2#H_JH#Z)
C:\Users\photoshop3\Documents\Visual Studio 2008\Projects\Lib2\Debug\Lib2.exe : fatal error LNK1120: 7 unresolved externals
The .lib is not included in your project. Make sure you are linking it in;
Configuration Properties -> Linker -> Input -> Additional Dependencies
Another altnerative is to simply copy the .lib to your project folder but don't, it's bound to create problems later on.
Sometimes the .lib is not shipped with the library, so you need to compile it yourself.
The README will tell you this. If this is the case, they usually ship with a .sln file you can open and the just compile it into a .lib file which you then reference in your main application, as I wrote above
Have you added the path of header files in the "Configuration Properties" --> "C/C++“ --> "General" --> "Additional Include Directories"?
The link gives you only the sources (including headerfiles) of libtorrent. You should compile this sources to get a .lib file. Add this .lib file to your client:
Configuration Properties/Linker/Input -> Additional Dependencies: libtorrent-rasterbar.lib
The best starting point for compiling should be the README file.
public: isn't the unresolved symbol. It's just there because the linker it trying to tell you that (most) of the unresolved symbols are public member functions.
It looks like you've included the header for "libtorrent", but not linked to the "libtorrent" library.
You have probably not linked with the torrent library or specified the wrong path to it so that the linker cannot find it.
If the input libraries are of 32bit and your are using them in building a 64bit it might be one of the reasons
For me, I had it included in my project, but it turned out that it was a plugin that was designed to not create an instance of in my unit test.