当构建我的c++程序时，我得到了错误消息
未定义的引用'vtable…
这个问题的原因是什么?我该怎么解决呢?
碰巧，我得到以下代码的错误(类的问题是CGameModule.)，我不能为我的生活理解问题是什么。起初，我认为这与忘记给虚拟函数赋予一个主体有关，但据我所知，一切都在这里。继承链有点长，但这里有相关的源代码。我不确定我还需要提供什么信息。
注意:这个错误似乎发生在构造函数中。
我的代码:
class CGameModule : public CDasherModule {
public:
CGameModule(Dasher::CEventHandler *pEventHandler, CSettingsStore *pSettingsStore, CDasherInterfaceBase *pInterface, ModuleID_t iID, const char *szName)
: CDasherModule(pEventHandler, pSettingsStore, iID, 0, szName)
{
g_pLogger->Log("Inside game module constructor");
m_pInterface = pInterface;
}
virtual ~CGameModule() {};
std::string GetTypedTarget();
std::string GetUntypedTarget();
bool DecorateView(CDasherView *pView) {
//g_pLogger->Log("Decorating the view");
return false;
}
void SetDasherModel(CDasherModel *pModel) { m_pModel = pModel; }
virtual void HandleEvent(Dasher::CEvent *pEvent);
private:
CDasherNode *pLastTypedNode;
CDasherNode *pNextTargetNode;
std::string m_sTargetString;
size_t m_stCurrentStringPos;
CDasherModel *m_pModel;
CDasherInterfaceBase *m_pInterface;
};
继承自…
class CDasherModule;
typedef std::vector<CDasherModule*>::size_type ModuleID_t;
/// \ingroup Core
/// @{
class CDasherModule : public Dasher::CDasherComponent {
public:
CDasherModule(Dasher::CEventHandler * pEventHandler, CSettingsStore * pSettingsStore, ModuleID_t iID, int iType, const char *szName);
virtual ModuleID_t GetID();
virtual void SetID(ModuleID_t);
virtual int GetType();
virtual const char *GetName();
virtual bool GetSettings(SModuleSettings **pSettings, int *iCount) {
return false;
};
private:
ModuleID_t m_iID;
int m_iType;
const char *m_szName;
};
哪个继承自....
namespace Dasher {
class CEvent;
class CEventHandler;
class CDasherComponent;
};
/// \ingroup Core
/// @{
class Dasher::CDasherComponent {
public:
CDasherComponent(Dasher::CEventHandler* pEventHandler, CSettingsStore* pSettingsStore);
virtual ~CDasherComponent();
void InsertEvent(Dasher::CEvent * pEvent);
virtual void HandleEvent(Dasher::CEvent * pEvent) {};
bool GetBoolParameter(int iParameter) const;
void SetBoolParameter(int iParameter, bool bValue) const;
long GetLongParameter(int iParameter) const;
void SetLongParameter(int iParameter, long lValue) const;
std::string GetStringParameter(int iParameter) const;
void SetStringParameter(int iParameter, const std::string & sValue) const;
ParameterType GetParameterType(int iParameter) const;
std::string GetParameterName(int iParameter) const;
protected:
Dasher::CEventHandler *m_pEventHandler;
CSettingsStore *m_pSettingsStore;
};
/// @}
#endif
我尝试了JaMIT的所有详细步骤，仍然被这个错误难住了。经过一番反复，我终于明白了。我太粗心了。您应该能够使用以下示例代码重现这个令人痛苦的错误。
[jaswantp@jaswant-arch build]$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl --with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit --enable-cet=auto --enable-checking=release --enable-clocale=gnu --enable-default-pie --enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id --enable-lto --enable-multilib --enable-plugin --enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch --disable-libunwind-exceptions --disable-werror gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.2.0 (GCC)
// CelesetialBody.h
class CelestialBody{
public:
virtual void Print();
protected:
CelestialBody();
virtual ~CelestialBody();
};
// CelestialBody.cpp
#include "CelestialBody.h"
CelestialBody::CelestialBody() {}
CelestialBody::~CelestialBody() = default;
void CelestialBody::Print() {}
// Planet.h
#include "CelestialBody.h"
class Planet : public CelestialBody
{
public:
void Print() override;
protected:
Planet();
~Planet() override;
};
// Planet.cpp
#include "Planet.h"
Planet::Planet() {}
Planet::~Planet() {}
void Print() {} // Deliberately forgot to prefix `Planet::`
# CMakeLists.txt
cmake_minimum_required(VERSION 3.12)
project (space_engine)
add_library (CelestialBody SHARED CelestialBody.cpp)
add_library (Planet SHARED Planet.cpp)
target_include_directories (CelestialBody PRIVATE ${CMAKE_CURRENT_LIST_DIR})
target_include_directories (Planet PRIVATE ${CMAKE_CURRENT_LIST_DIR})
target_link_libraries (Planet PUBLIC CelestialBody)
# hardened linker flags to catch undefined symbols
target_link_options(Planet
PRIVATE
-Wl,--as-needed
-Wl,--no-undefined
)
我们得到了我们最喜欢的误差。
$ mkdir build
$ cd build
$ cmake ..
$ make
[ 50%] Built target CelestialBody
Scanning dependencies of target Planet
[ 75%] Building CXX object CMakeFiles/Planet.dir/Planet.cpp.o
[100%] Linking CXX shared library libPlanet.so
/usr/bin/ld: CMakeFiles/Planet.dir/Planet.cpp.o: in function `Planet::Planet()':
Planet.cpp:(.text+0x1b): undefined reference to `vtable for Planet'
/usr/bin/ld: CMakeFiles/Planet.dir/Planet.cpp.o: in function `Planet::~Planet()':
Planet.cpp:(.text+0x3d): undefined reference to `vtable for Planet'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/Planet.dir/build.make:104: libPlanet.so] Error 1
make[1]: *** [CMakeFiles/Makefile2:97: CMakeFiles/Planet.dir/all] Error 2
make: *** [Makefile:103: all] Error 2
我在Planet.cpp中所做的事情当然应该通过这个技巧来解决
查看类定义。找到第一个非纯虚函数(不是“= 0”)，并且您提供了其定义(不是“= default”)的非内联虚函数。
JaMIT的回答。
如果有其他人尝试了以上所有方法，但没有任何效果，可能您也像我一样，不小心忘记给一个或多个成员函数加上<ClassName>::前缀。
要么我需要检查一下眼睛，要么我需要睡一会儿。
