error while loading shared libraries: ../../lib/libopencv_core.so

error while loading shared libraries: ../../lib/libopencv_core.so

原文：http://blog.chinaunix.net/uid-27134408-id-5122776.html

最近做OpenCV的交叉编译，参考了国内某大大的博客之后，成功编译出动态库文件，但运行时总是报错：
/rom/data/avt/test/cardetect/testso: error while loading shared libraries: ../../lib/libopencv_core.so: cannot open shared object file: No such file or directory
分析认为是运行时libopencv_highgui.so和libopencv_objdetect.so链接../../lib/libopencv_core.so时找不到库文件造成的。问题就出在libopencv_core.so前面奇怪的"../../lib/"相对路径。用readelf -d查看libopencv_highgui.so文件信息：
 

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1. readelf -d libopencv_highgui.so
2.  
3. Dynamic section at offset 0x50580 contains 30 entries:
4.   Tag Type Name/Value
5.  0x00000001 (NEEDED) Shared library: [../../lib/libopencv_core.so]
6.  0x00000001 (NEEDED) Shared library: [../../lib/libopencv_imgproc.so]
7.  0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
8.  0x00000001 (NEEDED) Shared library: [libm.so.6]
9.  0x00000001 (NEEDED) Shared library: [libgcc_s.so.1]
10.  0x00000001 (NEEDED) Shared library: [libc.so.6]
11.  0x0000000c (INIT) 0xa410
12.  0x0000000d (FINI) 0x49ed4
13.  0x00000019 (INIT_ARRAY) 0x50000
14.  0x0000001b (INIT_ARRAYSZ) 12 (bytes)
15.  0x0000001a (FINI_ARRAY) 0x5000c
16. ......

果然libopencv_highgui.so链接core库的时候把../../lib也加上去了。
我研究了半天也没找到这个路径是在哪里可以设置的，突然想到，google上国外友人似乎很少遇到这个问题。于是按照这篇文章又重编了opencv：
http://processors.wiki.ti.com/index.php/Building_OpenCV_for_ARM_Cortex-A8
其中编译过程中需要在toolchain.cmake中增加一项配置：
 

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1. set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )

否则cmake会从root path中寻找make和gcc\g++使用，这会产生类似expect ")"的错误信息。
之后按照步骤编译出动态库，再用readelf查看一下：
 

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1. readelf -d libopencv_objdetect.so
2.  
3. Dynamic section at offset 0x107628 contains 35 entries:
4.   Tag Type Name/Value
5.  0x00000001 (NEEDED) Shared library: [libopencv_core.so.2.4]
6.  0x00000001 (NEEDED) Shared library: [libopencv_imgproc.so.2.4]
7.  0x00000001 (NEEDED) Shared library: [libopencv_highgui.so.2.4]
8.  0x00000001 (NEEDED) Shared library: [libdl.so.2]
9.  0x00000001 (NEEDED) Shared library: [libpthread.so.0]
10.  0x00000001 (NEEDED) Shared library: [librt.so.1]
11.  0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
12. .........

这样放到arm下面运行，就会从当前目录下正确的找到core库了。