CMake error when building OpenCV - CMakeLists not match

Question

I tried to build OpenCV 3.1.0 on my Raspberry Pi 2B. Unfortunetly, when I trying:

cmake -D CMAKE_BUILD_TYPE=RELEASE \ -D CMAKE_INSTALL_PREFIX=/usr/local \ -D INSTALL_C_EXAMPLES=OFF \ -D INSTALL_PYTHON_EXAMPLES=OFF /home/pi/Downloads/opencv-3.1.0

It gave me a error :( :

CMake Error: The source "/home/pi/Downloads/opencv-3.1.0/CMakeLists.txt" does not match the source "/home/pi/Downloads/opencv-3.1.0/modules/CMakeLists.txt" used to generate cache. Re-run cmake with a different source directory.

I want to use OpenCV with C++ and Code::Bocks, which I have already installed. I can't found any solution on internet, so I will be very happy if smb help me. :) Forgot to say I using Raspbian Jezzy.

Solution 1

First, I hope you do run CMake outside your sources, in a separate directory. Not doing that is really not recommended

To understand the error message you have to know a little bit on how CMake works.

Basically, when you run

cd /path/to/opencv
mkdir build
cd build
cmake ..

CMake generates a cache in the build dir (It's a simple file named CMakeCache.txt). This file contains some information like:

• The path to the sources /path/to/opencv
• The path to the build dir /path/to/opencv/build
• The CMake Generator used (Ninja, Unix Makefiles ...)

If you ever re-run CMake and change one of these values, (by re-running cmake with different arguments, setting an other generotor or moving files), CMake will complain with this kind of message.

A good solution is then to delete the CMakeCache, or even the whole build dir to be safe.

Solution 2

The reason is you have used two version of cmake to generate the Makefile.

cd /path/to/opencv
rm -rf build
mkdir build
cd build
cmake ..

that will be work fine.

• Installing OpenCV 2.4.9 in Ubuntu 14.04 LTS http://www.samontab.com/web/2014/06/installing-opencv-2-4-9-in-ubuntu-14-04-lts/

Comments

[3Qax]

As you say, the solition was to delete build folder. Thanks for help :)

[gebbissimo]

I am using the CMake gui in windows. In addition to deleting the build directory I also (or only?) needed to activate "File > Delete Cache" in the GUI.

[C.J.]

I ran into this when a CMakeCache.txt file was somehow placed right at the roof of my c: directory.