尽管在cpp中有定义，但LNK2019构造函数中未解析的外部符号

debugcn 发表于 Dev

小白

我敢肯定这个问题已经被问过了，但是我已经尽我所能搜索了SO，但仍然找不到错误的确切原因。因此发布了一个新的。

我在我的项目中使用C ++库（txmpp）。该库已正确添加，但是我遇到了许多未解决的外部符号问题，主要是在我尝试使用的类的构造函数中。例如，在下面的类中-

xmppthread.h

#ifndef _HELLO_XMPPTHREAD_H_
#define _HELLO_XMPPTHREAD_H_

#include "../../thread.h"
#include "../../xmppclientsettings.h"
#include "xmpppump.h"

namespace txmpp {

class XmppThread: public txmpp::Thread, XmppPumpNotify, txmpp::MessageHandler {
  public:
    XmppThread();
    ~XmppThread();

    XmppClient* client() { return pump_->client(); }

    void ProcessMessages(int cms);
    void Login(const txmpp::XmppClientSettings & xcs);
    void Disconnect();

  private:
    XmppPump* pump_;

    void OnStateChange(txmpp::XmppEngine::State state);
    void OnMessage(txmpp::Message* pmsg);
};

}  // namespace txmpp

#endif  // _HELLO_XMPPTHREAD_H_

xmppthread.cc

#include "xmppthread.h"

#include <assert.h>
#include "../../prexmppauthimpl.h"
#include "../../xmppasyncsocketimpl.h"
#include "../../xmppclientsettings.h"

namespace txmpp {
namespace {

const uint32 MSG_LOGIN = 1;
const uint32 MSG_DISCONNECT = 2;

struct LoginData : public MessageData {
  LoginData(const XmppClientSettings& s) : xcs(s) {}
  virtual ~LoginData() {}
  XmppClientSettings xcs;
};

} // namespace

XmppThread::XmppThread() {
  pump_ = new XmppPump(this);
}

XmppThread::~XmppThread() {
  delete pump_;
}

void XmppThread::ProcessMessages(int cms) {
  Thread::ProcessMessages(cms);
}

void XmppThread::Login(const XmppClientSettings& xcs) {
  Post(this, MSG_LOGIN, new LoginData(xcs));
}

void XmppThread::Disconnect() {
  Post(this, MSG_DISCONNECT);
}

void XmppThread::OnStateChange(XmppEngine::State state) {
}

void XmppThread::OnMessage(Message* pmsg) {
  switch (pmsg->message_id) {
    case MSG_LOGIN: {
      assert(pmsg->pdata);
      LoginData* data = reinterpret_cast<LoginData*>(pmsg->pdata);
      pump_->DoLogin(data->xcs, new XmppAsyncSocketImpl(true),
                     new PreXmppAuthImpl());
      delete data;
      }
      break;
    case MSG_DISCONNECT:
      pump_->DoDisconnect();
      break;
    default:
      assert(false);
  }
}

}  // namespace hello

我收到以下错误-

1>XMPPController.obj : error LNK2019: unresolved external symbol "public: __thiscall txmpp::XmppThread::XmppThread(void)" (??0XmppThread@txmpp@@QAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)
1>XMPPController.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall txmpp::XmppThread::~XmppThread(void)" (??1XmppThread@txmpp@@UAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)

我通常仅在未提供函数定义（在这种情况下为构造函数/析构函数）的情况下才会看到此类链接器错误。但是，如您所见，该定义已包括在内。仅当我在项目中执行此操作时，才会生成此错误-

xmpp::XmppThread thread;

一旦删除声明语句，链接错误就会消失。问题是这些代码都不是我编写的，而是从txmpp库获取的。这个特定的类来自Google的libjingle库，所以我确定自己在这里犯了一些非常愚蠢的错误。

我不希望这个问题是“这是我的代码，请解决”。相反，我想知道在有声明的情况下仍可能发生未解决的外部符号错误的情况是什么（代码在那里提供了实现的证明）

有什么建议吗？

更新
这里是关闭强制启动横幅选项后获得的确切输出-

 1>LINK : warning LNK4075: ignoring '/INCREMENTAL' due to '/FORCE' specification
    1>AirPlaySystem.obj : warning LNK4075: ignoring '/EDITANDCONTINUE' due to '/OPT:LBR' specification
    1>LIBCMTD.lib(sscanf.obj) : warning LNK4006: _vsscanf already defined in s3e_d.lib(iwcrt_win32.obj); second definition ignored
    1>LIBCMTD.lib(strtoq.obj) : warning LNK4006: _strtof already defined in s3e_d.lib(iwcrt_common.obj); second definition ignored
    1>     Creating library Debug_BarnC_vc12_x86\BarnC.lib and object Debug_BarnC_vc12_x86\BarnC.exp
    1>XMPPController.obj : error LNK2019: unresolved external symbol "public: __thiscall txmpp::XmppThread::XmppThread(void)" (??0XmppThread@txmpp@@QAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)
    1>XMPPController.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall txmpp::XmppThread::~XmppThread(void)" (??1XmppThread@txmpp@@UAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)
    1>Debug_BarnC_vc12_x86\BarnC.s86 : fatal error LNK1120: 2 unresolved externals
    ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

更新2：这是添加详细链接程序命令行选项后的详细链接程序输出-

1>  Microsoft (R) Incremental Linker Version 12.00.31101.0
1>  Copyright (C) Microsoft Corporation.  All rights reserved.
1>  
1>  "/OUT:Debug_BarnC_vc12_x86\BarnC.s86" /INCREMENTAL /LIBPATH:d:/marmalade/7.4/modules/third_party/sqlite/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwutil/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/third_party/zlib/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/third_party/libpng/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iw2d/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwgx/atitools /LIBPATH:d:/marmalade/7.4/modules/iwgx/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwgl/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwgeom/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwresmanager/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwgxfont/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwui/lib/x86 /LIBPATH:d:/marmalade/7.4/modules/iwhttp/lib/x86 /LIBPATH:d:/marmalade/7.4/extensions/s3etxmpp/lib/x86 /LIBPATH:d:/marmalade/7.4/s3e/lib/x86 vc6_compat.lib sqlite_d.lib iwutil_d.lib jpeg_d.lib z_d.lib png_d.lib iw2d_d.lib ATI_Compress_MT_VC7.lib iwgx_d.lib iwgl_d.lib iwgeom_d.lib iwresmanager_d.lib iwgxfont_ttf_d.lib tiniconv_d.lib iwui_d.lib iwhttp_d.lib s3eTxmpp_d.lib s3e_cpp_d.lib s3e_d.lib s3e_api_iwgl.lib /NODEFAULTLIB:libcmt /MANIFEST:NO /DEBUG "/PDB:Debug_BarnC_vc12_x86\BarnC.pdb" /SUBSYSTEM:WINDOWS /OPT:NOREF /OPT:NOICF /TLBID:1 "/ENTRY:DllEntryPoint" /DYNAMICBASE /NXCOMPAT "/IMPLIB:Debug_BarnC_vc12_x86\BarnC.lib" /MACHINE:X86 /include:_IwMain /include:_raise /include:_DllEntryPoint@12 /force:multiple /VERBOSE:LIB /DLL Debug_BarnC_vc12_x86\AirPlaySystem.obj 
1>  Debug_BarnC_vc12_x86\CTextField.obj 
1>  Debug_BarnC_vc12_x86\Chat.obj 
1>  Debug_BarnC_vc12_x86\ChatController.obj 
1>  Debug_BarnC_vc12_x86\ChatGroup.obj 
1>  Debug_BarnC_vc12_x86\ChatMenu.obj 
1>  Debug_BarnC_vc12_x86\Contact.obj 
1>  Debug_BarnC_vc12_x86\ContactController.obj 
1>  Debug_BarnC_vc12_x86\HttpManager.obj 
1>  Debug_BarnC_vc12_x86\LoginMenu.obj 
1>  Debug_BarnC_vc12_x86\Main.obj 
1>  Debug_BarnC_vc12_x86\MainMenu.obj 
1>  Debug_BarnC_vc12_x86\MenuBase.obj 
1>  Debug_BarnC_vc12_x86\MenuController.obj 
1>  Debug_BarnC_vc12_x86\PVRTexTool_interface.obj 
1>  Debug_BarnC_vc12_x86\SimpleTouch.obj 
1>  Debug_BarnC_vc12_x86\UnivApp.obj 
1>  Debug_BarnC_vc12_x86\XMPPController.obj 
1>  Debug_BarnC_vc12_x86\md5c.obj 
1>LINK : warning LNK4075: ignoring '/INCREMENTAL' due to '/FORCE' specification
1>AirPlaySystem.obj : warning LNK4075: ignoring '/EDITANDCONTINUE' due to '/OPT:LBR' specification
1>  
1>  Searching libraries
1>      Searching d:/marmalade/7.4/modules/third_party/sqlite/lib/x86\sqlite_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwutil/lib/x86\iwutil_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86\jpeg_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/zlib/lib/x86\z_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libpng/lib/x86\png_d.lib:
1>      Searching d:/marmalade/7.4/modules/iw2d/lib/x86\iw2d_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/atitools\ATI_Compress_MT_VC7.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/lib/x86\iwgx_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgl/lib/x86\iwgl_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgeom/lib/x86\iwgeom_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwresmanager/lib/x86\iwresmanager_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgxfont/lib/x86\iwgxfont_ttf_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86\tiniconv_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwui/lib/x86\iwui_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwhttp/lib/x86\iwhttp_d.lib:
1>      Searching d:/marmalade/7.4/extensions/s3etxmpp/lib/x86\s3eTxmpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_cpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_api_iwgl.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\OLDNAMES.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\LIBCMTD.lib:
1>LIBCMTD.lib(sscanf.obj) : warning LNK4006: _vsscanf already defined in s3e_d.lib(iwcrt_win32.obj); second definition ignored
1>LIBCMTD.lib(strtoq.obj) : warning LNK4006: _strtof already defined in s3e_d.lib(iwcrt_common.obj); second definition ignored
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\uuid.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\kernel32.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/sqlite/lib/x86\sqlite_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwutil/lib/x86\iwutil_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86\jpeg_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/zlib/lib/x86\z_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libpng/lib/x86\png_d.lib:
1>      Searching d:/marmalade/7.4/modules/iw2d/lib/x86\iw2d_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/atitools\ATI_Compress_MT_VC7.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/lib/x86\iwgx_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgl/lib/x86\iwgl_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgeom/lib/x86\iwgeom_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwresmanager/lib/x86\iwresmanager_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgxfont/lib/x86\iwgxfont_ttf_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86\tiniconv_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwui/lib/x86\iwui_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwhttp/lib/x86\iwhttp_d.lib:
1>      Searching d:/marmalade/7.4/extensions/s3etxmpp/lib/x86\s3eTxmpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_cpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_api_iwgl.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\OLDNAMES.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\LIBCMTD.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\uuid.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\kernel32.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/sqlite/lib/x86\sqlite_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwutil/lib/x86\iwutil_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86\jpeg_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/zlib/lib/x86\z_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libpng/lib/x86\png_d.lib:
1>      Searching d:/marmalade/7.4/modules/iw2d/lib/x86\iw2d_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/atitools\ATI_Compress_MT_VC7.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/lib/x86\iwgx_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgl/lib/x86\iwgl_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgeom/lib/x86\iwgeom_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwresmanager/lib/x86\iwresmanager_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgxfont/lib/x86\iwgxfont_ttf_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86\tiniconv_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwui/lib/x86\iwui_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwhttp/lib/x86\iwhttp_d.lib:
1>      Searching d:/marmalade/7.4/extensions/s3etxmpp/lib/x86\s3eTxmpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_cpp_d.lib:
1>  
1>  Finished searching libraries
1>     Creating library Debug_BarnC_vc12_x86\BarnC.lib and object Debug_BarnC_vc12_x86\BarnC.exp
1>  
1>  Searching libraries
1>      Searching d:/marmalade/7.4/modules/third_party/sqlite/lib/x86\sqlite_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwutil/lib/x86\iwutil_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86\jpeg_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/zlib/lib/x86\z_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libpng/lib/x86\png_d.lib:
1>      Searching d:/marmalade/7.4/modules/iw2d/lib/x86\iw2d_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/atitools\ATI_Compress_MT_VC7.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/lib/x86\iwgx_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgl/lib/x86\iwgl_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgeom/lib/x86\iwgeom_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwresmanager/lib/x86\iwresmanager_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgxfont/lib/x86\iwgxfont_ttf_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86\tiniconv_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwui/lib/x86\iwui_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwhttp/lib/x86\iwhttp_d.lib:
1>      Searching d:/marmalade/7.4/extensions/s3etxmpp/lib/x86\s3eTxmpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_cpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_api_iwgl.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\OLDNAMES.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\LIBCMTD.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\uuid.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\kernel32.lib:
1>  
1>  Finished searching libraries
1>  
1>  Searching libraries
1>      Searching d:/marmalade/7.4/modules/third_party/sqlite/lib/x86\sqlite_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwutil/lib/x86\iwutil_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libjpeg/lib/x86\jpeg_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/zlib/lib/x86\z_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/libpng/lib/x86\png_d.lib:
1>      Searching d:/marmalade/7.4/modules/iw2d/lib/x86\iw2d_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/atitools\ATI_Compress_MT_VC7.lib:
1>      Searching d:/marmalade/7.4/modules/iwgx/lib/x86\iwgx_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgl/lib/x86\iwgl_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgeom/lib/x86\iwgeom_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwresmanager/lib/x86\iwresmanager_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwgxfont/lib/x86\iwgxfont_ttf_d.lib:
1>      Searching d:/marmalade/7.4/modules/third_party/tiniconv/lib/x86\tiniconv_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwui/lib/x86\iwui_d.lib:
1>      Searching d:/marmalade/7.4/modules/iwhttp/lib/x86\iwhttp_d.lib:
1>      Searching d:/marmalade/7.4/extensions/s3etxmpp/lib/x86\s3eTxmpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_cpp_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_d.lib:
1>      Searching d:/marmalade/7.4/s3e/lib/x86\s3e_api_iwgl.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\OLDNAMES.lib:
1>      Searching C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\lib\LIBCMTD.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\uuid.lib:
1>      Searching C:\Program Files (x86)\Windows Kits\8.1\lib\winv6.3\um\x86\kernel32.lib:
1>  
1>  Finished searching libraries
1>XMPPController.obj : error LNK2019: unresolved external symbol "public: __thiscall txmpp::XmppThread::XmppThread(void)" (??0XmppThread@txmpp@@QAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)
1>XMPPController.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall txmpp::XmppThread::~XmppThread(void)" (??1XmppThread@txmpp@@UAE@XZ) referenced in function "public: void __thiscall XMPPController::Init(void)" (?Init@XMPPController@@QAEXXZ)
1>Debug_BarnC_vc12_x86\BarnC.s86 : fatal error LNK1120: 2 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========