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Chapter-on-need-for-RTEMS-specific-cross-compiler

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Removed '-' character and provided definition list format
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Utkarsh Rai 2020-04-04 09:16:22 +05:30 committed by Gedare Bloom
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@ -3,6 +3,7 @@
.. Copyright (C) 2019 embedded brains GmbH .. Copyright (C) 2019 embedded brains GmbH
.. Copyright (C) 2019 Sebastian Huber .. Copyright (C) 2019 Sebastian Huber
.. Copyright (C) 2020 Chris Johns .. Copyright (C) 2020 Chris Johns
.. Copyright (C) 2020 Utkarsh Rai
.. _QuickStartTools: .. _QuickStartTools:
@ -76,3 +77,35 @@ source code used.
Add ``--verbose`` to the GCC command for the the verbose version details. Add ``--verbose`` to the GCC command for the the verbose version details.
Need for RTEMS-Specific Cross-Compiler
---------------------------------------------------------
New users are often confused as to why they cannot use their distribution's
cross-compiler for their target on rtems, e.g., the riscv64-linux-gnu or the
arm-none-eabi-gcc on RTEMS. Below mentioned are some of the reasons for using
the RTEMS cross-compiler.
Correct configuration of Newlib
Newlib is a C standard library implementation intended for use on embedded
systems. Most of the POSIX and libc support for RTEMS is derived from
Newlib. The RTEMS cross-compiler configures Newlib correctly for RTEMS.
Threading in GCC support libraries
Several threading packages in GCC such as Go threads (libgo), OpenMP
(libgomp), and OpenACC need to be customized according to RTEMS. This is
done by the RTEMS specific cross-compiler.
Provide preprocessor define __rtems__
The ``__rtems__`` preprocessor define is used to provide conditional code
compilation in source files that are shared with other projects e.g. in
Newlib or imported code from FreeBSD.
Multilib variants to match the BSP
RTEMS configures GCC to create separate runtime libraries for each
supported instruction set, floating point unit, vector unit, word size
(e.g. 32-bit and 64-bit), endianness, ABI, processor errata workarounds,
and so on in the architecture. These libraries are termed as :ref:`Multilib
<TargetArchitectures>` variants. Multilib variants to match the BSP are set
by selecting a specific set of machine options using the RTEMS
cross-compiler.