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Re: assembly: mov a memory word into register

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2021-11-12 at 19:19 +0100, Herbert Kleebauer wrote:
> > mov ah, 2
> > mov dl, [buff]  
> 
> This instruction doesn't exist, the compiler uses instead:
> 
> mov dl, buff

Well, no - in this specific example "mov dl, [buff]" does exist. It
loads whatever is at the location pointed out by buff (here: the word
0x82). But note that my previous program was an actual assembly
listing, not an assembly-inside-C abomination like in the first post.

"mov dl, [buff]" is, in fact, the same instruction as in "mov dl,
[0x82]", it is just that the assembler substitutes "buff" by its offset
at compile time:

00000000  B402              mov ah,0x2
00000002  8A161501          mov dl,[0x115]
00000006  CD21              int 0x21
00000008  B402              mov ah,0x2
0000000A  8A168200          mov dl,[0x82]
0000000E  CD21              int 0x21
00000010  B8004C            mov ax,0x4c00
00000013  CD21              int 0x21
00000015  82                db 0x82
00000016  00                db 0x00

My foolish mistake was to expect a similar behavior within an inline
assembly block when referencing a C pointer (which is different from an
assembly offset and implies - as you correctly pointed out in your
first reply - an extra layer of indirection).

Mateusz

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assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 14:35 +0100
  Re: assembly: mov a memory word into register "Kerr-Mudd, John" <admin@127.0.0.1> - 2021-11-12 16:52 +0000
  Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 17:53 +0100
    Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 18:40 +0100
      Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 19:19 +0100
        Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 20:07 +0100
          Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 22:18 +0100
      Re: assembly: mov a memory word into register rridge@csclub.uwaterloo.ca (Ross Ridge) - 2021-11-15 16:53 +0000
  Re: assembly: mov a memory word into register Rod Pemberton <noemail@basdxcqvbe.com> - 2021-11-14 20:53 -0500
    Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-15 09:31 +0100
      Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-15 12:10 +0100
        Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-15 13:02 +0100

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