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Newsgroups: comp.lang.ada
Date: Fri, 10 Jun 2022 05:16:40 -0700 (PDT)
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Subject: Re: Using pointers with inline assembly in Ada
From: NiGHTS <nights@unku.us>
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On Friday, June 10, 2022 at 1:28:17 AM UTC-4, roda...@gmail.com wrote:
> On 10/6/22 07:30, NiGHTS wrote:=20
> > declare=20
> > type ff is array (0 .. 10) of Unsigned_32;=20
> > pragma Pack(ff);=20
> > Flags : aliased ff :=3D (others =3D> 0);=20
> > Flag_Address : System.Address :=3D Flags'Address;=20
> > begin=20
> > Asm ( "movl %0, %%eax" &=20
> > "movl $1, (%%eax)" ,=20
> > Inputs =3D> System.Address'Asm_Input ("g", Flag_Address),=20
> > Clobber =3D> "eax",=20
> > Volatile =3D> true=20
> > );=20
> > Put_Line ("Output:" & Flags(0)'Img);=20
> > end;=20
> >
> If you are on a 64 bit machine, then I expect 'pragma Pack' might be=20
> the problem, as 2 consecutive array elements will fir into a single addre=
ss.=20
>=20
>=20
> Also, possibly use ...=20
>=20
> Flag_Address : System.Address :=3D Flags (Flags'First)'Address;=20
>=20
>=20
> Regards.

Thank you for your response. Unfortunately this didn't seem to work. I agre=
e that the pragma was misused, though that shouldn't have caused the error =
accessing the first element. I also am not entirely sure why there would be=
 a difference between the address of the first element versus the address o=
f the array itself (maybe that's just my C instincts kicking in).