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63 lines
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63 lines
3.6 KiB
ReStructuredText
.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 2012, 2016 Chris Johns <chrisj@rtems.org>
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.. _WhyBuildFromSource:
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Why Build from Source?
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----------------------
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The RTEMS Source Builder is not a replacement for the binary install systems
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you have with commercial operating systems or open source operating system
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distributions. Those products and distributions are critically important and
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are the base that allows the RSB to work. The RTEMS Source Builder sits
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somewhere between you manually entering the commands to build a tool set and a
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tool such as ``yum`` or ``apt-get`` to install binary packages made
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specifically for your host operating system. Building manually or installing a
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binary package from a remote repository are valid and real alternatives. The
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RSB provides the specific service of repeatably being able to build tool sets
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from source code. The process leaves you with the source code used to build
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the tools and the ability to rebuild it.
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If you are developing a system or product that has a long shelf life or is used
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in a critical piece of infrastructure that has a long life cycle being able to
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build from source is important. It insulates the project from the fast ever
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changing world of the host development machines. If your tool set is binary and
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you have lost the ability to build it you have lost a degree of control and
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flexibility open source gives you. Fast moving host environments are
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fantastic. We have powerful multi-core computers with huge amounts of memory
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and state of the art operating systems your development uses however the
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product or project you are part of may need to be maintained well past the life
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time of these host. Being able to build from source is an important and
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critical part of this process because you can move to a newer host and create
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an equivalent tool set.
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Building from source provides you with control over the configuration of the
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package you are building. If all or the most important dependent parts are
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built from source you limit the exposure to host variations. For example the
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GNU Compiler Collection (GCC) currently uses a number of third-party libraries
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internally (GMP, ISL, MPC, MPFR, etc.). If your validated compiler generating
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code for your target
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processor is dynamically linked against the host's version of these libraries
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any change in the host's configuration may effect you. The changes the host's
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package management system makes may be perfectly reasonable in relation to the
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distribution being managed however this may not extend to you and your
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tools. Building your tools from source and controlling the specific version of
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these dependent parts means you are not exposing yourself to unexpected and
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often difficult to resolve problems. On the other side you need to make sure
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your tools build and work with newer versions of the host operating
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system. Given the stability of standards based libraries like ``libc`` and ever
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improving support for standard header file locations this task is becoming
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easier.
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The RTEMS Source Builder is designed to be audited and incorporated into a
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project's verification and validation process. If your project is developing
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critical applications that needs to be traced from source to executable code in
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the target, you need to also consider the tools and how to track them.
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If your IT department maintains all your computers and you do not have suitable
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rights to install binary packages, building from source lets you create your
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own tool set that you install under your home directory. Avoiding installing
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any extra packages as a super user is always helpful in maintaining a secure
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computing environment.
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