Cmake Error: could not load cache. Trouble-shooting advice? [duplicate] - r

Question

System :
Linux anon-S 3.19.0-31-generic #36~14.04.1-Ubuntu SMP Thu Oct 8 10:21:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
CMake Version :
anon#anon-S:~/$ cmake --version
cmake version 3.2.2
Main CMakeLists.txt :
cmake_minimum_required(VERSION 3.0)
set(CMAKE_CXX_STANDARD 11)
add_subdirectory(${PROJECT_SOURCE_DIR}/src)
add_subdirectory(${PROJECT_SOURCE_DIR}/test)
But
anon#anon-S:/home/anon/project/build$ cmake ..
-- Configuring done
-- Generating done
-- Build files have been written to: /home/anon/project/
Build files have been written to: /home/anon/project/ instead /home/anon/project/build/
I haven't this problem on my Debian jessie with cmake 3.4.1 :
anon#anon-S:/home/anon/project/build$ cmake ..
-- The C compiler identification is GNU 5.2.1
-- The CXX compiler identification is GNU 5.2.1
-- 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 Doxygen: /usr/bin/doxygen (found version "1.8.11")
-- Configuring done
-- Generating done
-- Build files have been written to: /home/anon/project/build/

Answer 1

To clarify what happened here:
When running cmake <directory> it does one of two things:
If <directory> is a source directory (ie. has a CMakeLists.txt in it), it will run CMake on that source and use the current working directory as the build directory.
If <directory> is a build directory (ie. has a CMakeCache.txt in it), it will run CMake on whatever source directory was used to create the build directory.
Note that the latter case takes precedence over the first one. That is, if you do the following:
cd <src_dir>
cmake .
*oops, wrong directory, i didn't mean that*
cd build
cmake ..
You might expect that this will run CMake with <src_dir> as the source and build as the build directory. But because of the first accidental CMake run, <src_dir> is now also a build directory for an in-source build! Hence the second run will ignore everything that is in build and instead use src_dir as both the source and build directory.
This is indeed a very nasty issue, but fortunately it can be solved very quickly once you realize what's happening: Simply remove the CMakeCache.txt from <src_dir>.
Note that in newer CMake versions (3.13 and up), you can use the -S and -B command line options to disambiguate the meaning of the directory argument:
-S <path-to-source>
Path to root directory of the CMake project to
build.
-B <path-to-build>
Path to directory which CMake will use as
the root of build directory.
If the directory doesn’t already exist CMake will make it.