[Coco] Second eyes needed for C to ASM ABI strangeness.

[Walter Zambotti]

Yes.

I have posted my code on another thread in this list.

Regards


Walter

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Joel Rees
Sent: Saturday, 26 October 2019 11:19 AM
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject: Re: [Coco] Second eyes needed for C to ASM ABI strangeness.

So Walter, have you got anywhere with this?

2019年10月23日(水) 15:39 lost <lost at l-w.ca>:

> Looks like you may have an issue with value sizes and maybe endianness.
> You haven't included enough information though. We need to know what 
> you declared the functions as. Particularly the return types. If you 
> haven't declared the asm one, its return type will default to int 
> which is probably half the size of long. Depending on endianness and 
> calling convention that could mean the high order bits are saved in 
> the variable instead of the low order bits. The other cases may only 
> be working properly accidentally due to an accident of register allocation or something.
> -------- Original message --------From: Walter Zambotti < 
> zambotti at iinet.net.au> Date: 2019-10-23  00:13  (GMT-07:00) To: 
> 'CoCoList for Color Computer Enthusiasts' <coco at maltedmedia.com> 
> Subject: [Coco] Second eyes needed for C to ASM ABI strangeness. In 
> following code where I call two shift functions. One written in C and theother in assembly (both
> functions not shown): long val, val1, val2;short shft;   printf("%ld
> %ld\n", shift(val, shft), shiftasm(val, shft));  val1 = shift(val, 
> shft);
> val2 = shiftasm(val, shft);  printf("%ld %ld\n", val1, val2); where 
> val = 1 and shft = 1; outputs the following: 2 22 0 If I change: val2 
> = shiftasm(val, shft); to: val2 = 0 + shiftasm(val, shft); Then the 
> output
> is: 2 22 2 Which is now correct. It appears I cannot directly assign 
> the output of my asm function directlyto a variable without having 
> some sort of temporary expression such as "0 +"or passed to another 
> function such as printf. So I'm not sure what the C to asm ABI should 
> be! Any ideas? Walter
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