error: symbol(s) not found for architecture x86_64

更新Mac到10.9.2版本，同时更新了Xcode，这时候再用QT到时候发现调用OpenCV就出错：error: symbol(s) not found for architecture x86_64
看起来就是没有找到合适的lib文件，太坑爹了，之前还是用得好好的。
重装Xcode， 重装OpenCV，重装QT后无效。
后来千辛万苦终于找到结果了，大神在这里：
http://stackoverflow.com/questions/20342896/solved-qt5-1-qt5-2-mac-os-10-9-mavericks-xcode-5-0-2-undefined-symbols

因为OpenCV是用Xcode编译的，而新的Xcode调用的OS X 10.9，但是QT还没有更新，还是用10.6，所以编译后的OpenCV就不会被QT识别了。

解决：
更改 ../Qt5.2.0/5.2.0-rc1/clang_64/mkspecs/macx-clang/qmake.conf
文件中的

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;">QMAKE_MACOSX_DEPLOYMENT_TARGET </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent; color: rgb(128, 0, 0);">10.6</span></code>

改为

<code style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; white-space: inherit;"><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;">QMAKE_MACOSX_DEPLOYMENT_TARGET </span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="pln" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent;"> </span><span class="lit" style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: transparent; color: rgb(128, 0, 0);">10.9</span></code>

然后对QT对工程先清理，再rebuild，就可以编译了。

Qt5.1/Qt5.2
+ Mac OS 10.9 (Mavericks) + XCode 5.0.2, Undefined symbols for architecture x86_64

This issue is answered in this post

http://qt-project.org/forums/viewthread/35646/

and explained by sandy.martel

I quoted here

Qt binary distribution compile with -stdlib=libstdc++ to be compatible with 10.6, Xcode 5 on 10.9 will select -stdlib=libc++ by default (for OS X 10.7 and better only). So symbol using classes from the standard library (like std::string in this case) will not
resolve correctly at link time. This is why you’re seeing this error (Undefined symbols for architecture x86_64) . Look with which standard library opencv is built: otool -L libopencv_XXX.dylib. You’ll have to rebuild it with the right one or change Qt’s mkspec
to use the newer one.

I solve this by changing ../Qt5.2.0/5.2.0-rc1/clang_64/mkspecs/macx-clang/qmake.conf

from

QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.6

to

QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.9

And remember clean your project before rebuild.
http://stackoverflow.com/questions/20342896/qt5-1-qt5-2-mac-os-10-9-mavericks-xcode-5-0-2-undefined-symbols-for-archi