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Re: _mainCRTStartup/ctr0.S and thumb
- From: "Torsten at Robitzki dot de" <Torsten at Robitzki dot de>
- To: Richard Earnshaw <rearnsha at arm dot com>
- Cc: "newlib at sourceware dot org" <newlib at sourceware dot org>
- Date: Mon, 4 Aug 2014 13:25:10 +0200
- Subject: Re: _mainCRTStartup/ctr0.S and thumb
- Authentication-results: sourceware.org; auth=none
- References: <18ADFCA9-8CF6-4304-9ED7-2BBCE1627162 at Robitzki dot de> <53DF4DEC dot 9030508 at arm dot com>
Am 04.08.2014 um 11:10 schrieb Richard Earnshaw <email@example.com>:
> Cortex-m0 can only execute thumb code. It doesn't support the A32 (ARM)
> instruction set.
yes, and that's why this version fails to work on a cortex-m0. Why are there arm32 instructions in thumb/crt0.o? Is it possible to use the newlib with a cortex-m0 cpu and if, how would I have to configure it?
I've poked a little bit into other functions of the newlib and all, but _mainCRTStartup/_start seem to be correctly compiled to thumb instructions. So I can make use of the newlib except for functions that needs some initialization. Is there a subset of the C library functions that are known to be used without initialization?