lea eax,[ebx + 1.7E4]

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ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 14 Nov 2011, 23:38

Code:

; 1.7E4 == 4684D000h

lea eax, [ebx + 4684D000h]  ;"A" does compile

lea eax, [ebx + 1.7E4]               ;"B" does not compile (invalid name)

I don't understand why "B" is not allowed.
There is no reason to prohibit it.
It is the responsibility of the programmer to make sense of this,
but the compiler should not prohibit it.

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14 Nov 2011, 23:38

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 15 Nov 2011, 00:01

ouadji wrote:

It is the responsibility of the programmer to make sense of this,

That makes no sense. Floating point numbers are generally imprecise, and trying to use them as address offsets is silly.

15 Nov 2011, 00:01

typedef

Joined: 25 Jul 2010
Posts: 2909
Location: 0x77760000

typedef 15 Nov 2011, 00:19

Laugh Out Loud

15 Nov 2011, 00:19

smiddy

Joined: 31 Oct 2004
Posts: 557

smiddy 15 Nov 2011, 04:45

Rolling On The Floor Laughing My Ass Off

15 Nov 2011, 04:45

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Nov 2011, 09:48

it's not the compiler to choose what does make sense and what does not.
Here, it's not a matter about the sémantic field, but a matter of dialectic.
It seems that the top-flight thought is not accessible to everyone. Wink

Quote:

and trying to use them as address offsets is silly.

Why always "an address offset" ?
"lea" can be used for many other things and all algorithms are possible.

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I am not young enough to know everything (Oscar Wilde)-

15 Nov 2011, 09:48

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 15 Nov 2011, 10:39

Do you have a situation where it would make sense? What were you trying to do when you encountered this "problem"?

15 Nov 2011, 10:39

typedef

Joined: 25 Jul 2010
Posts: 2909
Location: 0x77760000

typedef 15 Nov 2011, 11:13

He thought FASM would convert 1.7E4 to it's 32 bit equivalent.

and therefore end up with lea eax, [ebx + 4684D000h]

What a fail.... still LOL-ing

15 Nov 2011, 11:13

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Nov 2011, 11:19

Quote:

Do you have a situation where it would make sense?

no

fasm should not limit the ability of the programmer by hypotheses about the sense or the nonsense of a line of code. it's not his role. Here, the compiler makes an assumption,his function is not to make assumptions.

(sorry for my bad english, i do my best)

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15 Nov 2011, 11:19

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8351
Location: Kraków, Poland

Tomasz Grysztar 15 Nov 2011, 11:28

It was allowed once: http://board.flatassembler.net/topic.php?p=12398#12398
But later (sometime around 1.59) it was disallowed once again, because people were keeping reporting this as a bug and with later parser improvements it was no longer needed even for macros.

15 Nov 2011, 11:28

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Nov 2011, 11:42

still "LOL-ing" typedef ? Wink

thank you Tomasz for this reply.

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15 Nov 2011, 11:42

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 15 Nov 2011, 19:22

tbh it made me laugh too.

1.7E4 has more than one possible representation, so it's probably a good thing that it has to be done specifically via macros/defines.

15 Nov 2011, 19:22

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 22 Nov 2011, 08:31

1.7E4 == 17000? 0x4268
What a confusion Razz

22 Nov 2011, 08:31

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 22 Nov 2011, 10:25

1.7E4f

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I am not young enough to know everything (Oscar Wilde)-

22 Nov 2011, 10:25

mindcooler

Joined: 01 Dec 2009
Posts: 423
Location: Västerås, Sweden

mindcooler 22 Nov 2011, 14:15

1.7e4.0

22 Nov 2011, 14:15

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 22 Nov 2011, 17:43

1.7E4.0

Code:

mov eax, 1.7E4.0 ;does not compile
mov eax, 1.7E4f  ;does compile

_________________
I am not young enough to know everything (Oscar Wilde)-

22 Nov 2011, 17:43

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