about header files used in score

[Joel Sherrill]

Zhongjie wrote:
> When you build gcc, you could tell gcc whether you have a c library, 
> when you tell gcc you do not have
> a c library, gcc will define "inhibit_libc", the stdio.h included by 
> libgcc2.c is in the section with "inhibit_libc"
> defined, when you build gcc to *-elf- or *-eabi- , such arm-elf-gcc or 
> arm-eabi-gcc, you do not need any
> c header files for the target.
While this is true for gcc in general, when you build an rtems toolset,
you always build the C library at the same time.  This means gcc does
have access to newlib.

RTEMS "OS proper" code shouldn't be depending on the C Library
much except for base C99 types and methods like the memory
and string code which doesn't require OS support.

It doesn't impact the design of the OS.  It is just a set of features
that are maintained by someone else and always there. 

--joel
>
> Regards
> Zhongjie
> -----Original Message-----
> *From*: Chris Johns <chrisj at rtems.org 
> <mailto:Chris%20Johns%20%3cchrisj at rtems.org%3e>>
> *To*: Zhongjie <zhurabbit at gmail.com 
> <mailto:Zhongjie%20%3czhurabbit at gmail.com%3e>>
> *Cc*: rtems-users at rtems.org <mailto:rtems-users at rtems.org>
> *Subject*: Re: about header files used in score
> *Date*: Mon, 15 Jun 2009 09:10:59 +1000
>
> Zhongjie wrote:
> > thanks for reply.
> > I am just beginning studying RTEMS, the newlib depends on a limited 
> > number of low level functions.
>
> Welcome.
>
> > In fact, we do not need any C library to build gcc as a cross complier, 
> > like arm-elf-gcc, only enable the c
> > language. what I concerns is that some part of RTEMS should can be 
> > compiled using those compiler.
>
> If you look in libgcc2.c you will see an include for stdio.h. I have always 
> needed some libc headers to build gcc.
>
> > Of course, with newlib support, RTEMS works well, it just a little 
> > confused logically for a beginner like me.
> > as my understanding, it is a c library depends on a os, not a os depends 
> > a c library.
> > I think we could define those types in rtems, then included by gcc and 
> > newlib, but not use those types directly in
> > a c library header files. it will make the architecture more clearly.
>
> GCC and newlib have all the types defined for a specific target and RTEMS uses 
> them.
>
> Regards
> Chris
>
>   


-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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