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| -rw-r--r-- | user/start/tools.rst | 33 |
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diff --git a/user/start/tools.rst b/user/start/tools.rst index c3f039b..1d83062 100644 --- a/user/start/tools.rst +++ b/user/start/tools.rst @@ -3,6 +3,7 @@ .. Copyright (C) 2019 embedded brains GmbH .. Copyright (C) 2019 Sebastian Huber .. Copyright (C) 2020 Chris Johns +.. Copyright (C) 2020 Utkarsh Rai .. _QuickStartTools: @@ -76,3 +77,35 @@ source code used. 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. |