Index
> Compiler Internals > Bug ? (value out of range) |
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Tomasz Grysztar 05 Nov 2011, 22:58
This is one of the side-effects of fasm's flaw that it calculates on 64-bit numbers instead of 65-bit, as it really should. 18446744073709551615 is the same as 0FFFFFFFFFFFFFFFFh, which fasm interpretes as -1. And -1 does fit into double word (as 0FFFFFFFFh). See the link for all the details, including some background on TASM, too.
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05 Nov 2011, 22:58 |
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ouadji 05 Nov 2011, 23:38
"fasm calculates on 64-bit numbers instead of 65-bit" I think this side-effect is more important than simply trigger a misinterpretation of -1. Fasm is a fantastic compiler, i think it would deserve a fix for this (old) problem. Just my opinion. mov ebx, $FFFFFFFFFFFFFFFF + 10 ;does compile mov ebx, $FFFFFFFF + 10 ;does not compile That said, I looked closely at your code about real numbers, nice work ! _________________ I am not young enough to know everything (Oscar Wilde)-  |
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05 Nov 2011, 23:38 |
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revolution 05 Nov 2011, 23:43
ouadji: Currently in fasm:
- addition and subtraction will never overflow. - Multiplication can overflow. |
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05 Nov 2011, 23:43 |
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ouadji 05 Nov 2011, 23:48
addition (and subtraction) will never overflow in this case, why this: mov eax, 0xFFFFFFFF + 1 ;---> value out of range _________________ I am not young enough to know everything (Oscar Wilde)- |
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05 Nov 2011, 23:48 |
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revolution 05 Nov 2011, 23:52
ouadji wrote:
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05 Nov 2011, 23:52 |
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revolution 05 Nov 2011, 23:54
BTW: In case you are curious here is the original topic about 65 bit processing. A small example of it in action.
http://board.flatassembler.net/topic.php?p=27758#27758 |
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05 Nov 2011, 23:54 |
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ouadji 06 Nov 2011, 00:01
Quote: It is not the addition that is overflowing. Code: mov ebx, $1'FFFF'FFFF ;33bits ==> "value out of range" _________________ I am not young enough to know everything (Oscar Wilde)- |
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06 Nov 2011, 00:01 |
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revolution 06 Nov 2011, 00:06
To test overflow use something like this:
Code: x=1 shl 63 + 1 shl 63 ;does not overflow y=0 - 1 shl 63 - 1 shl 63 ;does not overflow z=1 shl 63 * 1 shl 63 ;die |
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06 Nov 2011, 00:06 |
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