[PATCH] Chapter on need for RTEMS-specific cross-compiler

[Gedare Bloom]

Hi Utkarsh,

Thank you this looks pretty good. Did you build the docs with your
changes to see they look right to you?

On Thu, Mar 26, 2020 at 10:57 AM utkarsh.rai60 at gmail.com
<utkarsh.rai60 at gmail.com> wrote:
>
> ---
>  user/start/tools.rst | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/user/start/tools.rst b/user/start/tools.rst
> index c3f039b..63b6d17 100644
> --- a/user/start/tools.rst
> +++ b/user/start/tools.rst
> @@ -76,3 +76,34 @@ 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 can't use their distribution's
> +cross-compiler for their target on rtems, e.g., the riscv64-linux-gnu or the
> +arm-none-eabi-gcc. 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 multilib variants. Multilibs variants
> +  to match the BSP are set by selecting a specific set of machine options using
> +  the RTEMS cross-compiler.
> --
> 2.17.1
>
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