ch5 imageBasics程序make时报错

[bene-yan]

在做第五讲的OpenCV基本操作的实践，程序make时报错如下：

[ 50%] Building CXX object CMakeFiles/imageBasics.dir/imageBasics.cpp.o
[100%] Linking CXX executable imageBasics
/usr/bin/ld: 找不到 -lEigen3::Eigen
collect2: error: ld returned 1 exit status
CMakeFiles/imageBasics.dir/build.make:155: recipe for target 'imageBasics' failed
make[2]: *** [imageBasics] Error 1
CMakeFiles/Makefile2:67: recipe for target 'CMakeFiles/imageBasics.dir/all' failed
make[1]: *** [CMakeFiles/imageBasics.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

一开始有更多的类似/usr/bin/ld: 找不到 -l*** 的错误，但是通过建立相应的.so文件软链接的方式消除了。不过这个Eigen库不是没有.so文件吗，实在不知道怎么解决了。还望知道的朋友解答一下

[gaoxiang12]

你的cmakelist怎么写了？链到Eigen上去了吗？

[bene-yan]

感谢高博的回复！
Eigen是只需要include_dir就行吧？我的CMakeLists.txt是这样写的：

cmake_minimum_required(VERSION 2.8)

project(imageBasics)

set(CMAKE_CXX_FLAGS "-std=c++11")

find_package(OpenCV REQUIRED)

include_directories(${OpenCV_INCLUDE_DIRS})
include_directories("/usr/include/eigen3")

add_executable(imageBasics imageBasics.cpp)

target_link_libraries(imageBasics ${OpenCV_LIBS})

我运行从您的仓库中git clone过来的代码也是报同样的错误。
另外，安装依赖项的时候，libvtk5-dev提示无法安装，我装的是libvtk6-dev。所以一开始有很多类似报错都是/usr/bin/ld: 找不到 -ltk***。不知道是不是这个原因？我安装的OpenCV 版本是3.4.7

[gaoxiang12]

你上面贴的错误和opencv应该没关系。这个cmakelist也会报eigen的链接错误吗？

[bene-yan]

是的，用这个cmakelists也会报eigen的错误。然后我重新做了下ch3的useEigen，没有问题。

ch5的这个程序cmake时有一个warning，而且这个warning重复出了十多次，下面我只贴出了一段这样的waring。会不会是我的cmake的问题？

-- The C compiler identification is GNU 7.4.0
-- The CXX compiler identification is GNU 7.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found OpenCV: /usr/local (found version "3.4.7") 
-- Configuring done
CMake Warning (dev) at CMakeLists.txt:13 (add_executable):
  Policy CMP0028 is not set: Double colon in target name means ALIAS or
  IMPORTED target.  Run "cmake --help-policy CMP0028" for policy details.
  Use the cmake_policy command to set the policy and suppress this warning.

  Target "imageBasics" links to target "Eigen3::Eigen" but the target was not
  found.  Perhaps a find_package() call is missing for an IMPORTED target, or
  an ALIAS target is missing?
This warning is for project developers.  Use -Wno-dev to suppress it.
【重复】

-- Generating done
-- Build files have been written to: /home/bene-robot/slambook2/ch5/imageBasics/build

[bene-yan]

问题解决了！我改了cmakelist的写法，新的cmakelist如下：

cmake_minimum_required(VERSION 2.8)

project(imageBasics)

set(CMAKE_CXX_FLAGS "-std=c++11")

find_package(OpenCV REQUIRED)

include_directories(${OpenCV_INCLUDE_DIRS})

find_package(Eigen3 REQUIRED)
include_directories( EIGEN3_INCLUDE_DIRS)
#include_directories("/usr/include/eigen3")
message(${EIGEN3_INCLUDE_DIRS})

add_executable(imageBasics imageBasics.cpp)

target_link_libraries(imageBasics ${OpenCV_LIBS})

就是把#include_directories("/usr/include/eigen3")改成了

find_package(Eigen3 REQUIRED)
include_directories( EIGEN3_INCLUDE_DIRS)

是参考了这个链接https://stackoverflow.com/questions/12249140/find-package-eigen3-for-cmake

但是message输出的信息也是/usr/include/eigen3，不知道为什么直接用#include_directories("/usr/include/eigen3")就不行。