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Contents:
  1. The Build System
    1. Intro
    2. The process
    3. CMAKE: A new way to make good.
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The Build System

Intro

I could, and probably should, take the time to share a some historical information regarding how what is generally referred to as “the build system” came into existence. Why it came into the sequence in which it is, how it became adopted, and how it became nearly universal. I am sure, one way or another, Dennis Ritchie had something to do with it when he ported his new language, C++, to unix. Instead, we are going to just dive into it.

The process

The standard make system has three main parts.

  1. Configure
  2. Make
  3. Install

Sometimes, one must preconfigure before one can configuring, and often one wants to clean up after installation.

Making with Make

make and it’s cousin, gnu make, both accept a ridiculously plentiful amount of different flags. Way too many flags than to even begin listing here. But there are a few you might want to be familiar with, as they are used fairly often.

  • -k = Tells make to continue on with the build as long as the encountered error does not affect the resulting target.
  • -j(N) = This one is almost always added. N represents the number of threads the user would like to use for the build. This came into play after the creation of multi-core processors. Most often the flag is represented like the following. make -j$(procnum) Which tells make to use the same number of threads as there are processors available.

make also accepts commands. Of these commands, install and clean are the standard for use.

  • make install is used after make -j$(procnum), and tells make to install the target it just built.
  • make clean is used after make install, and tells make to cleanup the build dir after the target is installed.

CMAKE: A new way to make good.

	You make, I make, we all CMAKE...

Yes, I know these jokes are terrible, but anyways… Cmake is a software development platform that provides several tools to aid developers in the building, testing, and automation of software. What is important to remember is that cmake is not a build system itself, it is a generator for build files and configurations that are then used by other build systems. Cmake is cross-platform and compiler independent. So, if you want to dumb all the above down to the intellectual level of a potato, CMAKE makes building easier and faster.

Important flags in cmake

If you were to perform a standard build without the employment of cmake, because you wanted or needed to set local system specific variables to be configured for the build or for the target. You would pass most of these variables to the ./configure command during the configuration process, but there are also circumstances when these variables can be set during the make process. Now, if you were to employ cmake, they are required to be passed during the execution of the cmake command. Like so:

cmake -DCMAKE_CXX_COMPILER="clang++" -DCMAKE_INSTALL_PREFIX="/usr/local" -DCMAKE_INSTALL_SYSCONFDIR="/etc" -DCMAKE_CXX_FLAGS="-I/usr/local/include" -DCMAKE_CXX_FLAGS="-I/usr/local/include/inotify" .
  • Notice how each flag contains only one dash -, and then the capital letter D. No, I have no idea in this world why each flags starts this way. What is important is knowing that it does.
  • Also, notice how each flag contains a label, followed by the equal sign =, and then the value contained in matching double quotes "...".
  • The last two are different from the others, and very important. That define paths to be included during the build. Which is what the -I represents.