title: Why do I get this error message: "undefined reference to `PerformChat(char*, char*, char*, char*, char*)'"
body: <p>I am trying to compile my program that uses ChatScript libraries. This is my code inside a file named <code>main.cpp</code> :</p>
  
  <pre><code>#include &lt;iostream&gt;
  
  #include "common.h"
  
  using namespace std;
  
  
  char* output2;
  unsigned int InitSystem(int argc,char* argv[]);
  void InitStandalone();
  
  int main(int argc, char * argv[])
  {
  char * userID;
  userID="one";
  
  
  PerformChat("one",NULL,"hi",NULL,output2);
  
  cout&lt;&lt;output2;
  
      return 0;
  }
  </code></pre>
  
  <p>I tried to include all the ChatScript libraries, also I know the <code>performChat</code> function is within <code>mainSystem.h</code> file that I have included it too(as you can see its in the line 218:  <a href="https://github.com/bwilcox-1234/ChatScript/blob/master/SRC/mainSystem.h" rel="nofollow noreferrer">https://github.com/bwilcox-1234/ChatScript/blob/master/SRC/mainSystem.h</a>).</p>
  
  <p>But after trying to compile my program by this command :</p>
  
  <pre><code>g++ -std=c++11 main.cpp constructCode.cpp csocket.cpp dictionarySystem.cpp english.cpp evserver.cpp factSystem.cpp functionExecute.cpp infer.cpp jsmn.cpp json.cpp markSystem.cpp mongodb.cpp mysql.cpp os.cpp outputSystem.cpp patternSystem.cpp postgres.cpp privatesrc.cpp scriptCompile.cpp spellcheck.cpp systemVariables.cpp tagger.cpp testing.cpp textUtilities.cpp tokenSystem.cpp topicSystem.cpp userCache.cpp userSystem.cpp variableSystem.cpp -o myprogram
  </code></pre>
  
  <p>I got many of this errors!!</p>
  
  <pre><code>                                             ^
  /tmp/ccuVtYkV.o: In function `main':
  main.cpp:(.text+0x36): undefined reference to `PerformChat(char*, char*, char*, char*, char*)'
  /tmp/cc6Mhc8u.o: In function `TestIf(char*, FunctionResult&amp;, char*)':
  constructCode.cpp:(.text+0x5b): undefined reference to `trace'
  constructCode.cpp:(.text+0x203): undefined reference to `trace'
  constructCode.cpp:(.text+0x820): undefined reference to `trace'
  constructCode.cpp:(.text+0x9d5): undefined reference to `trace'
  constructCode.cpp:(.text+0xb62): undefined reference to `trace'
  /tmp/cc6Mhc8u.o:constructCode.cpp:(.text+0xbab): more undefined references to `trace' follow
  /tmp/cc6Mhc8u.o: In function `HandleIf(char*, char*, FunctionResult&amp;)':
  constructCode.cpp:(.text+0xd15): undefined reference to `always'
  constructCode.cpp:(.text+0xe75): undefined reference to `trace'
  constructCode.cpp:(.text+0x1086): undefined reference to `trace'
  constructCode.cpp:(.text+0x11c4): undefined reference to `trace'
  /tmp/cc6Mhc8u.o: In function `HandleLoop(char*, char*, FunctionResult&amp;)':
  constructCode.cpp:(.text+0x13ab): undefined reference to `trace'
  constructCode.cpp:(.text+0x14a7): undefined reference to `trace'
  /tmp/cc6Mhc8u.o:constructCode.cpp:(.text+0x298c): more undefined references to `trace' follow
  /tmp/ccWaC4y6.o: In function `fillAddr(std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt; const&amp;, unsigned short, sockaddr_in&amp;)':
  csocket.cpp:(.text+0x2320): undefined reference to `hostname'
  /tmp/ccWaC4y6.o: In function `Client':
  csocket.cpp:(.text+0x37bf): undefined reference to `always'
  csocket.cpp:(.text+0x3840): undefined reference to `port'
  csocket.cpp:(.text+0x389d): undefined reference to `port'
  csocket.cpp:(.text+0x3af1): undefined reference to `port'
  csocket.cpp:(.text+0x3b4e): undefined reference to `port'
  /tmp/ccWaC4y6.o: In function `RegressLoad(void*)':
  csocket.cpp:(.text+0x3f96): undefined reference to `revertBuffer'
  csocket.cpp:(.text+0x3fcb): undefined reference to `revertBuffer'
  csocket.cpp:(.text+0x401c): undefined reference to `revertBuffer'
  csocket.cpp:(.text+0x40b9): undefined reference to `port'
  /tmp/ccWaC4y6.o: In function `LogChat(long, char*, char*, char*, int, char*, char*)':
  csocket.cpp:(.text+0x4559): undefined reference to `version'
  /tmp/ccWaC4y6.o: In function `LaunchClient(void*)':
  csocket.cpp:(.text+0x4821): undefined reference to `pthread_create'
  /tmp/ccWaC4y6.o: In function `InternetServer()':
  csocket.cpp:(.text+0x4a01): undefined reference to `pthread_create'
  csocket.cpp:(.text+0x4a1f): undefined reference to `pthread_create'
  csocket.cpp:(.text+0x4a38): undefined reference to `pthread_join'
  /tmp/ccWaC4y6.o: In function `ServerTransferDataToClient()':
  csocket.cpp:(.text+0x4a8d): undefined reference to `ourMainOutputBuffer'
  /tmp/ccWaC4y6.o: In function `HandleTCPClient(void*)':
  csocket.cpp:(.text+0x5454): undefined reference to `outputLength'
  /tmp/ccWaC4y6.o: In function `GrabPort()':
  csocket.cpp:(.text+0x5777): undefined reference to `interfaceKind[abi:cxx11]'
  csocket.cpp:(.text+0x5799): undefined reference to `port'
  csocket.cpp:(.text+0x57c7): undefined reference to `port'
  csocket.cpp:(.text+0x57d6): undefined reference to `interfaceKind[abi:cxx11]'
  /tmp/ccWaC4y6.o: In function `MainChatbotServer()':
  csocket.cpp:(.text+0x5940): undefined reference to `quitting'
  csocket.cpp:(.text+0x5a7d): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5a83): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5a8e): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5aa1): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5afa): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5b1b): undefined reference to `ourMainOutputBuffer'
  csocket.cpp:(.text+0x5b3b): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5b43): undefined reference to `PerformChat(char*, char*, char*, char*, char*)'
  csocket.cpp:(.text+0x5b5b): undefined reference to `Restart()'
  csocket.cpp:(.text+0x5bb0): undefined reference to `ourMainInputBuffer'
  csocket.cpp:(.text+0x5bd6): undefined reference to `ourMainOutputBuffer'
  /tmp/ccwtMWsK.o: In function `ClearWhereInSentence()':
  dictionarySystem.cpp:(.text+0x35d): undefined reference to `documentMode'
  /tmp/ccwtMWsK.o: In function `AllocateWhereInSentence(WORDENTRY*)':
  dictionarySystem.cpp:(.text+0x5ce): undefined reference to `documentMode'
  /tmp/ccwtMWsK.o: In function `UseDictionaryFile(char*)':
  dictionarySystem.cpp:(.text+0xefc): undefined reference to `language'
  dictionarySystem.cpp:(.text+0xf1f): undefined reference to `language'
  dictionarySystem.cpp:(.text+0xf3a): undefined reference to `language'
  /tmp/ccwtMWsK.o: In function `ReadForeignPosTags(char*)':
  dictionarySystem.cpp:(.text+0x10a0): undefined reference to `readBuffer'
  dictionarySystem.cpp:(.text+0x10d9): undefined reference to `readBuffer'
  /tmp/ccwtMWsK.o: In function `BuildDictionary(char*)':
  dictionarySystem.cpp:(.text+0x1402): undefined reference to `language'
  dictionarySystem.cpp:(.text+0x157f): undefined reference to `language'
  dictionarySystem.cpp:(.text+0x165c): undefined reference to `users'
  dictionarySystem.cpp:(.text+0x16ba): undefined reference to `CreateSystem()'
  /tmp/ccwtMWsK.o: In function `StoreWord(char*, unsigned long long)':
  dictionarySystem.cpp:(.text+0x2915): undefined reference to `server'
  /tmp/ccwtMWsK.o: In function `ShowStats(bool)':
  dictionarySystem.cpp:(.text+0x31bb): undefined reference to `volleyStartTime'
  dictionarySystem.cpp:(.text+0x31c8): undefined reference to `inputSentenceCount'
  dictionarySystem.cpp:(.text+0x31d2): undefined reference to `inputSentenceCount'
  dictionarySystem.cpp:(.text+0x322b): undefined reference to `tokenCount'
  dictionarySystem.cpp:(.text+0x3266): undefined reference to `tokenCount'
  dictionarySystem.cpp:(.text+0x326c): undefined reference to `inputSentenceCount'
  </code></pre>