最近有人让我想起了我长大时(不久前(经常玩的一个游戏，我想试着让它重新运行。它已经有近十年没有开发了，所以没有任何预构建的包可以工作。我拿到了游戏和旧版本CEGUI库的源代码，然后开始工作。
我修复了制作过程中的一些问题，但现在我被这个错误消息卡住了：
/usr/bin/ld: smc-video.o: in function `SMC::cVideo::Init_CEGUI_Fake() const':
video.cpp:107: undefined reference to `CEGUI::NullRenderer::create()'
我对C++没有什么经验，但我设法理解了这是一个无法找到函数声明的链接器问题。所以我查看了应该有声明的文件，实际上有一个创建函数：
/*!
brief
Create an NullRenderer object
*/
static NullRenderer& create();
但它不是错过了一个宣言吗？我已经检查了链接器是否在正确的文件中查找函数，因为向代码中添加｛｝确实可以防止错误(当然会导致不同的错误(，这让我相信make没有错。我还从CEGUINullRenderer.h中查找了includes中的声明，但没有找到。(没有CEGUINullRenderer.cpp(
我试着从create函数返回一个NullRenderer对象，但这并没有真正起作用。我在这里错过了什么？
video.cpp(直到抛出错误的部分(：
/***************************************************************************
* video.cpp - General video functions
*
* Copyright (C) 2005 - 2011 Florian Richter
***************************************************************************/
/*
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "../video/video.h"
#include "../gui/hud.h"
#include "../user/preferences.h"
#include "../core/framerate.h"
#include "../video/font.h"
#include "../core/game_core.h"
#include "../video/img_settings.h"
#include "../input/mouse.h"
#include "../video/renderer.h"
#include "../core/main.h"
#include "../core/math/utilities.h"
#include "../core/i18n.h"
#include "../core/math/size.h"
#include "../core/filesystem/filesystem.h"
#include "../core/filesystem/resource_manager.h"
#include "../gui/spinner.h"
// SDL
#include "SDL_opengl.h"
// CEGUI
#include "CEGUIDefaultResourceProvider.h"
#include "CEGUIDefaultLogger.h"
#include "CEGUIExceptions.h"
#include "CEGUIWindowFactoryManager.h"
#include "CEGUIImagesetManager.h"
#include "CEGUIFontManager.h"
#include "CEGUIWindowManager.h"
#include "CEGUISchemeManager.h"
#include "falagard/CEGUIFalWidgetLookManager.h"
#include "elements/CEGUIProgressBar.h"
#include "RendererModules/Null/CEGUINullRenderer.h"
// png
#include <png.h>
#ifndef PNG_COLOR_TYPE_RGBA
#define PNG_COLOR_TYPE_RGBA PNG_COLOR_TYPE_RGB_ALPHA
#endif
namespace SMC
{
/* *** *** *** *** *** *** *** Video class *** *** *** *** *** *** *** *** *** *** */
cVideo :: cVideo( void )
{
m_opengl_version = 0;
m_double_buffer = 0;
m_rgb_size[0] = 0;
m_rgb_size[1] = 0;
m_rgb_size[2] = 0;
m_default_buffer = GL_BACK;
m_max_texture_size = 512;
m_audio_init_failed = 0;
m_joy_init_failed = 0;
m_geometry_quality = cPreferences::m_geometry_quality_default;
m_texture_quality = cPreferences::m_texture_quality_default;
SDL_VERSION( &wm_info.version );
#ifdef __unix__
glx_context = NULL;
#endif
m_render_thread = boost::thread();
m_initialised = 0;
}
cVideo :: ~cVideo( void )
{
}
void cVideo :: Init_CEGUI_Fake( void ) const
{
// create fake Resource Provider
CEGUI::DefaultResourceProvider *rp = new CEGUI::DefaultResourceProvider();
// set Resource Provider directories
if( CEGUI::System::getDefaultXMLParserName().compare( "XercesParser" ) == 0 )
{
// This is needed for Xerces to specify the schemas location
rp->setResourceGroupDirectory( "schemas", DATA_DIR "/" GAME_SCHEMA_DIR "/" );
}
// get a directory to dump the CEGUI log
#ifdef _WIN32
// fixme : Workaround for std::string to CEGUI::String utf8 conversion. Check again if CEGUI 0.8 works with std::string utf8
CEGUI::String log_dump_dir = (const CEGUI::utf8*)((Get_Temp_Directory() + "cegui.log").c_str());
#else
CEGUI::String log_dump_dir = "/dev/null";
#endif
// create fake system and renderer
pGuiSystem = &CEGUI::System::create( CEGUI::NullRenderer::create(), rp, NULL, NULL, NULL, "", log_dump_dir );
}
CEGUINullRenderer.h:
/***********************************************************************
filename: CEGUINullRenderer.h
created: Fri Jan 15 2010
author: Eugene Marcotte
*************************************************************************/
/***************************************************************************
* Copyright (C) 2004 - 2010 Paul D Turner & The CEGUI Development Team
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
***************************************************************************/
#ifndef _CEGUINullRenderer_h_
#define _CEGUINullRenderer_h_
#include "../../CEGUIRenderer.h"
#include "../../CEGUISize.h"
#include "../../CEGUIVector.h"
#include <vector>
#include <map>
#if (defined( __WIN32__ ) || defined( _WIN32 )) && !defined(CEGUI_STATIC)
# ifdef NULL_GUIRENDERER_EXPORTS
# define NULL_GUIRENDERER_API __declspec(dllexport)
# else
# define NULL_GUIRENDERER_API __declspec(dllimport)
# endif
#else
# define NULL_GUIRENDERER_API
#endif
#if defined(_MSC_VER)
# pragma warning(push)
# pragma warning(disable : 4251)
#endif
// Start of CEGUI namespace section
namespace CEGUI
{
class NullGeometryBuffer;
class NullTexture;
class NullRenderTarget;
//! CEGUI::Renderer implementation for no particular engine
class NULL_GUIRENDERER_API NullRenderer : public Renderer
{
public:
/*!
brief
Convenience function that creates all the necessary objects
then initialises the CEGUI system with them.
This will create and initialise the following objects for you:
- CEGUI::NullRenderer
- CEGUI::DefaultResourceProvider
- CEGUI::System
return
Reference to the CEGUI::NullRenderer object that was created.
*/
static NullRenderer& bootstrapSystem();
/*!
brief
Convenience function to cleanup the CEGUI system and related objects
that were created by calling the bootstrapSystem function.
This function will destroy the following objects for you:
- CEGUI::System
- CEGUI::DefaultResourceProvider
- CEGUI::NullRenderer
note
If you did not initialise CEGUI by calling the bootstrapSystem function,
you should e not call this, but rather delete any objects you created
manually.
*/
static void destroySystem();
/*!
brief
Create an NullRenderer object
*/
static NullRenderer& create();
//! destory an NullRenderer object.
static void destroy(NullRenderer& renderer);
// implement CEGUI::Renderer interface
RenderingRoot& getDefaultRenderingRoot();
GeometryBuffer& createGeometryBuffer();
void destroyGeometryBuffer(const GeometryBuffer& buffer);
void destroyAllGeometryBuffers();
TextureTarget* createTextureTarget();
void destroyTextureTarget(TextureTarget* target);
void destroyAllTextureTargets();
Texture& createTexture();
Texture& createTexture(const String& filename, const String& resourceGroup);
Texture& createTexture(const Size& size);
void destroyTexture(Texture& texture);
void destroyAllTextures();
void beginRendering();
void endRendering();
void setDisplaySize(const Size& sz);
const Size& getDisplaySize() const;
const Vector2& getDisplayDPI() const;
uint getMaxTextureSize() const;
const String& getIdentifierString() const;
protected:
//! default constructor.
NullRenderer();
//! common construction things.
void constructor_impl();
//! destructor.
virtual ~NullRenderer();
//! String holding the renderer identification text.
static String d_rendererID;
//! What the renderer considers to be the current display size.
Size d_displaySize;
//! What the renderer considers to be the current display DPI resolution.
Vector2 d_displayDPI;
//! The default rendering root object
RenderingRoot* d_defaultRoot;
//! The default RenderTarget (used by d_defaultRoot)
NullRenderTarget* d_defaultTarget;
//! container type used to hold TextureTargets we create.
typedef std::vector<TextureTarget*> TextureTargetList;
//! Container used to track texture targets.
TextureTargetList d_textureTargets;
//! container type used to hold GeometryBuffers we create.
typedef std::vector<NullGeometryBuffer*> GeometryBufferList;
//! Container used to track geometry buffers.
GeometryBufferList d_geometryBuffers;
//! container type used to hold Textures we create.
typedef std::vector<NullTexture*> TextureList;
//! Container used to track textures.
TextureList d_textures;
//! What the renderer thinks the max texture size is.
uint d_maxTextureSize;
};
} // End of CEGUI namespace section
#if defined(_MSC_VER)
# pragma warning(pop)
#endif
#endif // end of guard _CEGUINullRenderer_h_
您已经声明了它，这意味着编译器很乐意编译它。声明就像函数的名称：编译器知道函数存在，并且可以编译调用它的代码。
但为了链接它，您必须在该函数的定义(实现(中进行链接。链接器告诉您，它没有您声明的函数的实际实现。
很可能你的链接行是错误的，几乎可以肯定的是，你要么根本忘记把库放在链接行上，要么把它放错了地方，但由于你没有向我们提供任何关于生成错误消息的链接命令或你用来链接的makefile规则的信息，我们无法提供帮助。