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August 9th, 2005, 05:25 AM
#1
fatal error LNK1120: 2 unresolved externals
hi i m new in vc++ enviroment i have an problem arrived
i have a code of udpdump which capture a packet from network and show but it is in dot c extension class i have rewrite this code in vc soo i made object of class udpdump and use in my another program
but it had 2 error when i make a header files and source file for this class can anyone help me i required a urgent response
the error which occur when i compile the code r
1-- UdpDum1.obj : error LNK2001: unresolved external symbol "struct pcap * __cdecl pcap_open(char const *,int,int,int,struct pcap_rmtauth *,char *)" (?pcap_open@@YAPAUpcap@@PBDHHHPAUpcap_rmtauth@@PAD@Z)
2--UdpDum1.obj : error LNK2001: unresolved external symbol "int __cdecl pcap_findalldevs_ex(char *,struct pcap_rmtauth *,struct pcap_if * *,char *)" (?pcap_findalldevs_ex@@YAHPADPAUpcap_rmtauth@@PAPAUpcap_if@@0@Z)
3--Debug/TestPacketCapturing.exe : fatal error LNK1120: 2 unresolved externals
will any body tell me the reason and solution of that error ???
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August 9th, 2005, 05:42 AM
#2
Re: fatal error LNK1120: 2 unresolved externals
Those are not compiler errors, those are linker errors.
Simply, the linker is trying to find these functions ( pcap_open, pcap_findalldevs_ex) and the linker can't find them.
1) Where are these functions located? Are they in another library? If so, you need to add the library to your project.
2) Are these functions in another source file? If so, you need to add those source files to your project.
3) Are these 'C' functions and not C++ functions? If so, then you need to change the declaration of the functions to "extern 'C'", since the C++ compiler has mangled the names of the functions to different names in the object file, and the linker is looking for the mangled name instead of the straight 'C' name of the function.
So you have three things to check, and the problem is one or more of the above.
Regards,
Paul McKenzie
Last edited by Paul McKenzie; August 9th, 2005 at 05:44 AM.
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August 9th, 2005, 07:16 AM
#3
Re: fatal error LNK1120: 2 unresolved externals
these functions is in other header files i add these files in my project but i think u r might b these function in c soo plz will u tell me how i use extern keyword in the function header file buz i have just header file there not the definition of that function
int pcap_findalldevs_ex(char *source, struct pcap_rmtauth *auth, pcap_if_t **alldevs, char *errbuf);
above is the difinition of function soo i write
extern'C' int pcap_findalldevs_ex(char *source, struct pcap_rmtauth *auth, pcap_if_t **alldevs, char *errbuf);
but it also give error soo plz will u guide me the right way i m really thankful to u
regards
s ali mehdi
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August 9th, 2005, 10:19 AM
#4
Re: fatal error LNK1120: 2 unresolved externals
Hi samedhi,
I have sent you a reply on how to resolve the linker errors. Have u received it?
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October 27th, 2007, 01:36 AM
#5
Re: fatal error LNK1120: 2 unresolved externals
Hi,
I am new to vc++ enviroment .
The errors which occured when i build the code are
capture_ten_pack.obj : error LNK2001: unresolved external symbol _pcap_open_live
capture_ten_pack.obj : error LNK2001: unresolved external symbol _pcap_lookupdev
Debug/capture_ten_pack.exe : fatal error LNK1120: 3 unresolved externals
Error executing link.exe.
capture_ten_pack.exe - 4 error(s), 0 warning(s)
I would appriciate anybody who make this code will work.
10Q
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November 24th, 2010, 11:31 AM
#6
Re: fatal error LNK1120: 2 unresolved externals
I had a similiar error. check your constructors if you ahve defined any. Mine worked when I just commented out my constructors, but hten again there was nothing my constructors were doing anyway so it didnt impact me.
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November 24th, 2010, 12:43 PM
#7
Re: fatal error LNK1120: 2 unresolved externals
Maybe you should check the date of a thread before you post.
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January 13th, 2011, 01:02 AM
#8
fatal error LNK1120: 2 unresolved externals
Greetings to the day.
I work now for the first time with the xercesc-library .iam using xerces 3.1.1.when i use this xerces alone i didnot find any errors, but if i use this along with delta3D i get the following errors.I already checked envoronment variables.Thanks in Advance
: fatal error LNK1120: 2 unresolved externals
: error LNK2019: unresolved external symbol "__declspec(dllimport) public: static class xercesc_3_1:OMImplementation * __cdecl xercesc_3_1:OMImplementationRegistry::getDOMImplementation(unsigned short const *)" (__imp_?getDOMImplementation@DOMImplementationRegistry@xercesc_3_1@@SAPAVDOMImplementation@2@PBG@Z) referenced in function "public: virtual void __thiscall clientSite::PostFrame(double)" (?PostFrame@clientSite@@UAEXN@Z)
: error LNK2019: unresolved external symbol "__declspec(dllimport) public: static unsigned short * __cdecl xercesc_3_1::XMLString::transcode(char const * const,class xercesc_3_1::MemoryManager * const)" (__imp_?transcode@XMLString@xercesc_3_1@@SAPAGQBDQAVMemoryManager@2@@Z) referenced in function "public: virtual void __thiscall clientSite::PostFrame(double)" (?PostFrame@clientSite@@UAEXN@Z)
debug\trial2.exe : fatal error LNK1120: 2 unresolved externals
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April 14th, 2012, 12:13 AM
#9
Re: fatal error LNK1120: 2 unresolved externals
ok, so, im using Visual C++ 2008 Express Edition and i'm trying to include other header files (such as IntBinaryTree.h), i understand that i actually have to 1. create the header file. 2. save it in the project folder along side the .cpp file. and 3.(?) well.. for (3) ive tried several things.. tools>options>project&solutions>vc++ directories > include files > and setting it to the path of where my header files will be saved.. which is i guess.. ../..visual studio/projects.. ive also tried... idk ive tried a lot of stuff and its aggravating me. Here are my error messages:
Error 1: error LNK2019: unresolved external symbol "public: void __thiscall IntBinaryTree::insertNode(int)" (?insertNode@IntBinaryTree@@QAEXH@Z) referenced in function _wmain Program 20-1 Binary Tree's.obj
Error2: error LNK2019: unresolved external symbol "private: void __thiscall IntBinaryTree:estroySubTree(struct IntBinaryTree::TreeNode *)" (?destroySubTree@IntBinaryTree@@AAEXPAUTreeNode@1@@Z) referenced in function "public: __thiscall IntBinaryTree::~IntBinaryTree(void)" (??1IntBinaryTree@@QAE@XZ) Program 20-1 Binary Tree's.obj
Error3: fatal error LNK1120: 2 unresolved externals C:\Users\Chris\Documents\Visual Studio 2008\Projects\Program 20-1 Binary Tree's\Debug\Program 20-1 Binary Tree's.exe
let me ask it this way..
how do i add additional header files (other than ones that come with the download of visual studio 2008 Express Edition) ??
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April 14th, 2012, 01:10 AM
#10
Re: fatal error LNK1120: 2 unresolved externals
wow just realizing the dates on the posts.
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April 14th, 2012, 07:55 AM
#11
Re: fatal error LNK1120: 2 unresolved externals
Originally Posted by Eric225
wow just realizing the dates on the posts. [...]
Well, though in deed digging up old threads like this one is not really appreciated, the fact that you posted in it is an indication that users (not just you, of course) sometimes are looking for answers in them. So, for you as well as others who may come across that thread later on, here's a proposed solution to your problem:
It sounds like you did store the source files you created in the right place, and in this case you usually don't need to do any manual configuration about the include directories. Your description of the problem, though, suggests that you may not actually have made them part of the project. That would be done automatically if you'd have created them using the "Add new item" button (right next to the "New project" button, at least in my VC++ 2010). If you already have the files but forgot to add them to the project, you may use "Add existing item" instead. You can tell whether files are part of the project by looking at the Solution Explorer: If they show up there, they're part of the project.
Not adding new files to the project actually isn't really an uncommon mistake, BTW...
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