Why is Travis not recognising installed CMake in script? - cmake

Question

I'm trying to put together a Travis CI script for my application, which requires CMake 3.5 or greater. The entire Travis script can be found here. Following advice I found elsewhere, I use the following to install CMake:
install:
- DEPS_DIR="${TRAVIS_BUILD_DIR}/deps"
- mkdir -p ${DEPS_DIR} && cd ${DEPS_DIR}
- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
CMAKE_URL="https://cmake.org/files/v3.7/cmake-3.7.2-Linux-x86_64.tar.gz";
mkdir cmake && travis_retry wget --no-check-certificate --quiet -O - ${CMAKE_URL} | tar --strip-components=1 -xz -C cmake;
export PATH=${DEPS_DIR}/cmake/bin:${PATH};
else
brew outdated cmake || brew upgrade cmake;
fi
- cmake --version
Then I fill out the build matrix with various OS/compiler combinations, and finally I run a Python installation script (see here):
before_script:
- cd "${TRAVIS_BUILD_DIR}"
script:
- ./install.py --compiler=$COMPILER
The Python script essentially just calls cmake and make, the first CMakeLists.txt can be found here.
The OSX builds which install CMake using Homebrew works perfectly. However, all of the Linux builds fail at the script stage due to CMake not meeting the minimum requirement:
CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
CMake 3.5 or higher is required. You are running version 3.2.2
Even though CMake 3.7 was successfully installed during install:
$ cmake --version
cmake version 3.7.2
What am I doing wrong?

Answer 1

This is strange, the preinstalled version of CMake (= v3.2 on Travis) is used instead of the newer one – but only when called from Python.
You can try these:
Solution 1: Remove the CMake shipped by Travis
This will prevent the usage of the older version. If this doesn't work (eg. maybe because "Cmake isn't found"), this will show the actual reason of the problem.
You can add this to your linux branch of the install step:
sudo apt-get purge cmake
Or:
sudo apt-get remove cmake
(Possible you need to add -y for confirmation, so it becomes remove -y).
Solution 2: Use the CMake installer
Installation through the CMake Installer is a much cleaner way. It turned out the be the faster one on Travis btw.
...
- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
CMAKE_INSTALLER=install-cmake.sh
curl -sSL https://cmake.org/files/v3.7/cmake-3.7.2-Linux-x86_64.sh -o ${CMAKE_INSTALLER}
chmod +x ${CMAKE_INSTALLER}
sudo ./${CMAKE_INSTALLER} --prefix=/usr/local --skip-license
else
...
I'm using curl instead of wget + travis_retry, but this doesn't matter. You can still use them as before.
If both don't work, you should check where the Python script looks for executables.