Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.lang.c
Subject: Re: question about linker
Date: Wed, 11 Dec 2024 16:26:08 +0200
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On Wed, 11 Dec 2024 11:57:40 +0000
bart <bc@freeuk.com> wrote:

> On 11/12/2024 09:18, Michael S wrote:
> > On Wed, 11 Dec 2024 05:37:15 -0000 (UTC)
> > antispam@fricas.org (Waldek Hebisch) wrote:  
> 
> >> You are exagerating and that does not help communication.  In this
> >> group there were at least one serious poster claiming to write code
> >> depending only on features from older C standard.  
> > 
> > For some definition of "serious".
> >   
> >> People like this
> >> presumably would care if some "toy" compiler discoverd
> >> non-compliance. Concerning tcc, they have explicit endorsment from
> >> gawk developer: he likes compile speed and says that gawk compiles
> >> fine using tcc.
> >>
> >> In may coding I use gcc extentions when I feel that there is
> >> substantial gain.  But for significant part of my code I prefer
> >> to portablility, and that may include avoiding features not
> >> supported by lesser compilers.  I the past tcc was not able
> >> to compile code which I consider rather ordinary C, and due
> >> to this and lack of support for my main target I did not use
> >> tcc.  But tcc improved, ATM I do not know if it is good enough
> >> for me, but it passed initial tests, so I have no reason to
> >> disregard it.
> >>
> >> BTW: IME "exotic" tools and targets help with finding bugs.
> >> So even if you do not normally need to compile with some
> >> compiler it makes sense to check if it works.
> >>  
> > 
> > I would think that the main reason for David Brown's absence of
> > interest in tcc is simply because tcc do not have back ends for
> > targets that he cares about.
> > In particular, Arm port appears to be abandoned in 2003, so quite
> > likely tcc can't generate code that runs on MCUs with ARMv7-M
> > architecture that happens to be released first in the same year and
> > officially named in the 2004.  
> 
> I remember running TCC on both RPi1 (2012) and RPi4 (2019). That
> would be ARM32 (some version of ARMv7 I guess; I find ARM model
> numbers bewildering).
> 
> It's possible I also tried TCC in the ARM64 mode of RPi4.
> 

ARMv7-AR architecture supports both fixed-width encoding (what's
named A32 in ARMv8 docs) and variable-width encoding (T32 in ARMv8
docs) a.k.a. Thumb-2
ARMv7-M on the other hand supports only variable-width encoding.

RPIi1 is ARM11 which is  architecturally ARMv6 (i.e. before T32).
RPi4 is Cortex-A72 which is  architecturally ARMv8-A.
Both of them can run fixed-width 32-bit encoded (A32) code fine. 

Overwhelming majority of microcontrollers are based on various Cortex-M
cores (Cortex-M4 is most popular by far) and they can't run such code.

> 
> So it sounds rather unlikely that TCC doesn't support ARM.
> 

But at least from the little docs that I was able to locate it looks
likely that it does not support Thumb-2.