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Re: Compile Assembly and C files together

Subject Re: Compile Assembly and C files together
Newsgroups comp.lang.c, comp.sys.raspberry-pi, comp.programming
References (10 earlier) <p7rs5o$ijd$2@dont-email.me> <p7tiqm$hl5$2@dont-email.me> <87muzh4nhk.fsf@LkoBDZeT.terraraq.uk> <p7tk7d$r1p$1@dont-email.me> <p7u3qu$v3u$1@dont-email.me>
From Richard Damon <Richard@Damon-Family.org>
Message-ID <MbAoC.56073$4z5.29691@fx17.iad> (permalink)
Organization Forte - www.forteinc.com
Date 2018-03-09 13:16 -0500

Cross-posted to 3 groups.

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On 3/9/18 8:56 AM, Tauno Voipio wrote:
> On 9.3.18 11:30, The Natural Philosopher wrote:
>> On 09/03/18 09:17, Richard Kettlewell wrote:
>>> The Natural Philosopher <tnp@invalid.invalid> writes:
>>>> On 08/03/18 17:33, mm0fmf wrote:
>>>>> On 08/03/2018 15:27, Martin Gregorie wrote:
>>>>>> On Thu, 08 Mar 2018 13:34:57 +0000, The Natural Philosopher wrote:
>>>>>>> I would at least put in a bit more
>>>>>>>
>>>>>>> int myfunction(int bufflth, char* buff)
>>>>>>>       {
>>>>>>>          return (int)buff[bufflth-1];
>>>>>>>       }
>>>>>>>
>>>>>>> So you know where on the stack buff and bufflth are...
>>>>>>
>>>>>> Why would you want to know that? All the assembler operations 
>>>>>> using the
>>>>>> arguments will be inside myfunction() and, unless the code is 
>>>>>> calculating
>>>>>> a result to be returned and used elsewhere, the returned value is
>>>>>> probably to report success or failure.
>>>>>>
>>>>>
>>>>> If it returns success or failure, why return 1 of 4 billion possible
>>>>> values?
>>>>
>>>> Another personm who has never coded assmebler for C..
>>>>
>>>> It not what you are rurining, its how to access (bufflth, char* buff)
>>>> which are LOCAL stack based variables.
>>>
>>> The first few args are passed in registers on many modern systems. See
>>> e.g. 
>>> http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf 
>>>
>>> for instance.
>>>
>>
>> Even so, the method still reveals WHICH registers
>>
>> But it is not a feature of the ARM per se, merely a convention.
>>
>> I assume gcc follows it, but there is no gurantee
> 
> GCC follows the ARM EABI specification:
> 
>   - stack on 8 byte boundaries,
>   - arguments in r0 - r3
>   - return value in r0
> 
> I still suspect that the OP does not have a clue of the assembly
> code he's attempting to link in.
> 

The EABI goes a bit farther, as there are some register the called 
function must preserve (if it changes them, it must save them first) and 
other register the caller can freely change, and if the callee needs 
them preserved must save them before the call. This choice is actually 
enshrined in the interrupt processing (at least on some ARMs, I would 
have to check if true for all the variants), as an interrupt will save 
all the registers that a normal function is allowed to change without 
saving, thus making ISR routines normal void fun(void) functions.

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Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-06 19:20 +0800
  Re: Compile Assembly and C files together druck <news@druck.org.uk> - 2018-03-06 13:53 +0000
    Re: Compile Assembly and C files together Rob Morley <nospam@ntlworld.com> - 2018-03-06 14:59 +0000
      Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-06 16:35 +0100
    Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-06 23:01 +0800
  Re: Compile Assembly and C files together ray carter <ray@zianet.com> - 2018-03-06 15:44 +0000
    Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-07 00:07 +0800
      Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-07 22:39 +0200
        Re: Compile Assembly and C files together "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-03-08 18:18 +0800
          Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 12:37 +0000
            Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 13:13 +0000
              Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-08 13:34 +0000
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-08 15:27 +0000
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-08 17:33 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:06 +0000
                Re: Compile Assembly and C files together Richard Kettlewell <invalid@invalid.invalid> - 2018-03-09 09:17 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:30 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 15:56 +0200
                Re: Compile Assembly and C files together bartc <bc@freeuk.com> - 2018-03-09 14:13 +0000
                Re: Compile Assembly and C files together Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2018-03-09 11:14 -0500
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:44 +0000
                Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-09 17:16 +0100
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 11:19 -0600
                Re: Compile Assembly and C files together bartc <bc@freeuk.com> - 2018-03-09 18:11 +0000
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 13:41 -0600
                Re: Compile Assembly and C files together David Brown <david.brown@hesbynett.no> - 2018-03-09 19:20 +0100
                Re: Compile Assembly and C files together Robert Wessel <robertwessel2@yahoo.com> - 2018-03-09 13:48 -0600
                Re: Compile Assembly and C files together Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2018-03-09 13:16 -0500
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 18:29 +0000
                Re: Compile Assembly and C files together Jack Fearnley <jack@alcor.concordia.ca> - 2018-03-09 19:07 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 19:13 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-10 13:16 -0600
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-11 19:39 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 01:16 -0500
                Re: Compile Assembly and C files together David Taylor <david-taylor@blueyonder.co.uk.invalid> - 2018-03-12 06:39 +0000
                Re: Compile Assembly and C files together Martin Gregorie <martin@mydomain.invalid> - 2018-03-12 20:49 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 16:11 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 14:58 -0500
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 20:38 +0000
                Re: Compile Assembly and C files together scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 16:06 +0000
                Re: Compile Assembly and C files together Michael J. Mahon <mjmahon@aol.com> - 2018-03-12 14:58 -0500
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:27 +0200
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:40 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:30 +0200
                Re: Compile Assembly and C files together Richard Damon <Richard@Damon-Family.org> - 2018-03-09 13:16 -0500
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 21:33 +0200
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-09 17:40 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 17:47 +0000
                Re: Compile Assembly and C files together mm0fmf <none@invalid.com> - 2018-03-09 18:05 +0000
                Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-09 09:05 +0000
                Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-09 16:01 +0200
          Re: Compile Assembly and C files together Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-03-08 17:25 +0200
  Re: Compile Assembly and C files together The Natural Philosopher <tnp@invalid.invalid> - 2018-03-07 07:36 +0000

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