### Lei Mao

Machine Learning, Artificial Intelligence, Computer Science.

# Build CMake with SSL Support

### Introduction

Recently I started to see some inconsistency of compile for one particular program using CMake in different environments. While the CMake versions do vary in different environments, the inconsistency is a problem of downloading some files from internet. At first I thought it is an internet connecting or port issue, I quickly eliminated this possibility since using wget to get those files does not have any problems. After doing some Google, I found that building CMake natively using the official installation protocol does not have SSL support. Without SSL support, there will be problem to download files using https protocol. The problem source is likely to be that the libcurl library which comes with the CMake installation package for building CMake was not built with SSL support, and this is still nox fixed in the latest version 3.14.4.

One way to get around is to install CMake using apt on Ubuntu. That particular CMake distribution has built-in SSL support. The only problem is that the CMake version (3.10.2) is not the latest, which might not meet the requirement of some of the projects.

Someone suggests to use curl libraries from the system, which are likely built with SSL support, to build CMake. However, when I tried to use that method to build CMake, I was notified that it cannot find curl libraries from my system while I do have different kind of libcurl.so.* installed. There are also some other more complicated methods posted, but I just don’t want to even try them, since I just have to install a libcurl.so that the CMake installation program could find and the problem should be fixed.

### Solution

It turns out that the solution is simple and straightforward. libcurl4-openssl-dev provides the curl libraries required for building CMake. This is the simplest complete solution I have seen so far.

$cd /tmp$ sudo apt-get install libcurl4-openssl-dev
$wget https://github.com/Kitware/CMake/releases/download/v3.14.4/cmake-3.14.4.tar.gz$ tar -xf cmake-3.14.4.tar.gz
$cd cmake-3.14.4$ ./bootstrap --system-curl --parallel=16 # Use parallel argument to accelerate the process
$make -j16 # Use j argument to accelerate the process$ sudo make install


Alternatively, installing using the sh file also seems to work.

$cd /tmp$ wget https://github.com/Kitware/CMake/releases/download/v3.14.4/cmake-3.14.4-Linux-x86_64.sh
$chmod +x cmake-3.14.4-Linux-x86_64.sh$ sudo ./cmake-3.14.4-Linux-x86_64.sh --prefix=/usr/local --exclude-subdir --skip-license
\$ rm ./cmake-3.14.4-Linux-x86_64.sh # Optional


### Final Remarks

I have been enjoying using apt to manage my software libraries since it is always easy to install, upgrade, and especially uninstall. To uninstall some programs that were not installed via apt, I need to keep the installations files in case some day in the future I will have to do a sudo make uninstall, which is not favored. I wish there could be the CMake Ubuntu distribution could be always up-to-date because CMake is really important.

This SSL support “bug” might be fixed by Kitware in the future release. But it should have been fixed a long time ago since it was an old problem.