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我试图按照https://code.google.com/p/wkhtmltopdf/wiki/compilation的指示在Linux机器上编译wkhtmltopdf-qt。为什么gcc链接器没有看到我的析构函数？
现在我被卡住链接器拒绝链接。它打印了几个错误，但引起我注意的一个是：
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a(AccessibilityRenderObject.o): In function `WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()':
AccessibilityRenderObject.cpp:(.text._ZN7WebCore25AccessibilityRenderObjectD0Ev+0x5): undefined reference to `WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()'
这很奇怪，至少可以说。首先，因为链接器声称析构函数试图引用自身和下一个 - 因为它没有这样做！疯狂的东西... 无论如何，一切似乎都被定义了。请注意以下几点：
[email protected]:~$ nm --defined-only -C -A /home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a | grep ~AccessibilityRenderObject
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a:AccessibilityRenderObject.o:0000000000000000 T WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a:AccessibilityRenderObject.o:0000000000000000 T WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a:AccessibilityRenderObject.o:0000000000000000 T WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()
[email protected]:~/wkhtmltopdf-qt/src/3rdparty/webkit/Source/WebCore/accessibility$
接下来，在文件AccessibilityRenderObject.cpp：
#include <wtf/unicode/CharacterNames.h>
using namespace std;
namespace WebCore {
using namespace HTMLNames;
AccessibilityRenderObject::AccessibilityRenderObject(RenderObject* renderer)
: AccessibilityObject()
, m_renderer(renderer)
, m_ariaRole(UnknownRole)
, m_childrenDirty(false)
, m_roleForMSAA(UnknownRole)
{
m_role = determineAccessibilityRole();
#ifndef NDEBUG
m_renderer->setHasAXObject(true);
#endif
}
AccessibilityRenderObject::~AccessibilityRenderObject()
{
ASSERT(isDetached());
}
因此，析构函数定义就好了。但我更进一步 - 我再次编译AccessibilityRenderObject.cpp，这次停在预处理器。肯定是地狱的析构函数有：
class AccessibilityRenderObject : public AccessibilityObject {
protected:
AccessibilityRenderObject(RenderObject*);
public:
static PassRefPtr<AccessibilityRenderObject> create(RenderObject*);
virtual ~AccessibilityRenderObject();
.
.
.
AccessibilityRenderObject::~AccessibilityRenderObject()
{
((void)0);
}
用来编译该文件（以及许多其他）的编译行是这样的：
g++ -c -m64 -pipe -Wall -Wextra -Wreturn-type -fno-strict-aliasing -Wcast-align -Wchar-subscripts -Wformat-security -Wreturn-type -Wno-unused-parameter -Wno-sign-compare -Wno-switch -Wno-switch-enum -Wundef -Wmissing-noreturn -Winit-self -Wno-c++0x-compat -ffunction-sections -fdata-sections -O2 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -D_REENTRANT -DNDEBUG -DBUILDING_QT__=1 -DNDEBUG -DQT_ASCII_CAST_WARNINGS -DENABLE_XSLT=0 -DENABLE_WEB_TIMING=0 -DENABLE_JAVASCRIPT_DEBUGGER=1 -DENABLE_DATABASE=1 -DENABLE_EVENTSOURCE=1 -DENABLE_OFFLINE_WEB_APPLICATIONS=1 -DENABLE_DOM_STORAGE=1 -DENABLE_ICONDATABASE=1 -DENABLE_CHANNEL_MESSAGING=1 -DENABLE_DIRECTORY_UPLOAD=0 -DENABLE_FILE_SYSTEM=0 -DENABLE_QUOTA=0 -DENABLE_SQLITE=1 -DENABLE_DASHBOARD_SUPPORT=0 -DENABLE_FILTERS=1 -DENABLE_XPATH=1 -DENABLE_WCSS=0 -DENABLE_SHARED_WORKERS=1 -DENABLE_WORKERS=1 -DENABLE_XHTMLMP=0 -DENABLE_DETAILS=1 -DENABLE_METER_TAG=1 -DENABLE_PROGRESS_TAG=1 -DENABLE_BLOB=1 -DENABLE_NOTIFICATIONS=1 -DENABLE_INPUT_SPEECH=0 -DENABLE_INSPECTOR=1 -DENABLE_3D_RENDERING=1 -DENABLE_WEB_AUDIO=0 -DENABLE_WEBGL=0 -DENABLE_MEDIA_STATISTICS=0 -DENABLE_VIDEO_TRACK=0 -DENABLE_TOUCH_ICON_LOADING=0 -DENABLE_ANIMATION_API=0 -DENABLE_SVG=1 -DENABLE_SVG_FONTS=1 -DENABLE_SVG_FOREIGN_OBJECT=1 -DENABLE_SVG_ANIMATION=1 -DENABLE_SVG_AS_IMAGE=1 -DENABLE_SVG_USE=1 -DENABLE_DATALIST=1 -DENABLE_TILED_BACKING_STORE=1 -DENABLE_NETSCAPE_PLUGIN_API=1 -DENABLE_WEB_SOCKETS=1 -DWTF_USE_QT_BEARER=1 -DENABLE_TOUCH_EVENTS=1 -DENABLE_VIDEO=0 -DENABLE_VIDEO=0 -DSQLITE_CORE -DSQLITE_OMIT_LOAD_EXTENSION -DSQLITE_OMIT_COMPLETE -DXP_UNIX -DENABLE_NETSCAPE_PLUGIN_METADATA_CACHE=1 -DBUILDING_JavaScriptCore -DBUILDING_WTF -DBUILDING_WEBKIT -DQT_MAKEDLL -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -I../../../../../mkspecs/linux-g++-64 -I. -I../../../../../include/QtCore -I../../../../../include/QtNetwork -I../../../../../include/QtGui -I../../../../../include -I../JavaScriptCore -I../../Source -I../ThirdParty -I../JavaScriptCore/assembler -I../JavaScriptCore/bytecode -I../JavaScriptCore/bytecompiler -I../JavaScriptCore/heap -I../JavaScriptCore/dfg -I../JavaScriptCore/debugger -I../JavaScriptCore/interpreter -I../JavaScriptCore/jit -I../JavaScriptCore/parser -I../JavaScriptCore/profiler -I../JavaScriptCore/runtime -I../JavaScriptCore/wtf -I../JavaScriptCore/wtf/gobject -I/home/ubuntu/wkhtmltopdf-qt/src/3rdparty/webkit/Source/JavaScriptCore/wtf/symbian -I../JavaScriptCore/wtf/unicode -I../JavaScriptCore/yarr -I../JavaScriptCore/API -I../JavaScriptCore/ForwardingHeaders -I../JavaScriptCore/generated -Ibridge/qt -Ipage/qt -Iplatform/graphics/qt -Iplatform/network/qt -Iplatform/qt -I../WebKit/qt/Api -I../WebKit/qt/WebCoreSupport -I. -Iaccessibility -Ibindings -Ibindings/generic -Ibridge -Icss -Idom -Idom/default -Iediting -Ifileapi -Ihistory -Ihtml -Ihtml/canvas -Ihtml/parser -Ihtml/shadow -Iinspector -Iloader -Iloader/appcache -Iloader/archive -Iloader/cache -Iloader/icon -Imathml -Inotifications -Ipage -Ipage/animation -Iplatform -Iplatform/animation -Iplatform/audio -Iplatform/graphics -Iplatform/graphics/filters -Iplatform/graphics/filters/arm -Iplatform/graphics/texmap -Iplatform/graphics/transforms -Iplatform/image-decoders -Iplatform/leveldb -Iplatform/mock -Iplatform/network -Iplatform/sql -Iplatform/text -Iplatform/text/transcoder -Iplugins -Irendering -Irendering/mathml -Irendering/style -Irendering/svg -Istorage -Isvg -Isvg/animation -Isvg/graphics -Isvg/graphics/filters -Isvg/properties -Itesting -Iwebaudio -Iwebsockets -I/home/ubuntu/wkhtmltopdf-qt/src/3rdparty/webkit/Source/WebCore/wml -Iworkers -Ixml -Ibridge/jsc -Ibindings/js -I/home/ubuntu/wkhtmltopdf-qt/src/3rdparty/webkit/Source/WebCore/bindings/js/specialization -Ibridge/c -Itesting/js -Igenerated -I../../Source -I../../include -I../include/QtWebKit -I../include -I../../../sqlite -I/usr/X11R6/include -I.moc/release-static -o .obj/release-static/AccessibilityRenderObject.o accessibility/AccessibilityRenderObject.cpp
最后失败的链接器命令行是这样的：
g++ -Wl,-rpath-link,/home/ubuntu/wkhtmltopdf-qt/lib -m64 -Wl,-O1 -Wl,-rpath,/home/ubuntu/wkhtmltopdf-qt/src/3rdparty/webkit/Source/lib -Wl,-rpa
th,/home/ubuntu/wkqt/lib -Wl,-rpath,/home/ubuntu/wkqt/lib -o tst_qwebframe .obj/release-static/tst_qwebframe.o .obj/release-static/qrc_tst_qweb
frame.o -L/home/ubuntu/wkhtmltopdf-qt/lib -L/usr/X11R6/lib64 -L/home/ubuntu/wkhtmltopdf-qt/lib -lQtWebKit -L../../WebCore/release -L../../Ja
vaScriptCore/release -L/usr/X11R6/lib64 -Wl,--start-group -lwebcore -lQtWebKit -Wl,--end-group -ljscore -lQtTest -lQtGui -lXrender -lXext -lX11
-lQtNetwork -lQtCore -lm -ldl -lrt -lpthread -lXrender -lXext -lX11 -lm
而且所有参照上述析构函数的链接错误是：
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a(AccessibilityRenderObject.o): In function `WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()':
AccessibilityRenderObject.cpp:(.text._ZN7WebCore25AccessibilityRenderObjectD2Ev+0x3): undefined reference to `vtable for WebCore::AccessibilityRenderObject'
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a(AccessibilityRenderObject.o): In function `WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()':
AccessibilityRenderObject.cpp:(.text._ZN7WebCore25AccessibilityRenderObjectD0Ev+0x5): undefined reference to `WebCore::AccessibilityRenderObject::~AccessibilityRenderObject()'
有许多可疑的链接错误，如：
/home/ubuntu/wkhtmltopdf-qt/lib/libwebcore.a(AccessibilityMenuList.o):(.data.rel.ro._ZTIN7WebCore21AccessibilityMenuListE[typeinfo for WebCore:
:AccessibilityMenuList]+0x10): undefined reference to `typeinfo for WebCore::AccessibilityRenderObject'
但据我可以看到所有的虚函数是正确声明的定义并在所有的源代码树的不makefile文件提及RTTI在所有。
任何人都可以向我解释发生了什么事吗？
如果向链接器命令添加“-Wl， - gc-sections”，有什么区别？ – 2013-03-25 03:58:10
这很神奇！有效！请将它打包为答复，我会将其标记为答案。 – mark 2013-03-25 09:24:40