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Index > Compiler Internals > [feature requast] Extended ASCII characters compliler "bug"

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Joined: 25 Jun 2017
Posts: 2
If you try to use eASCII characters (using the windows's eASCII spaicel keyboard feature (alt+0->255) ) in fasm's text editor and compile it you will end up with the hax value of the ASCII character '?' or with their (UNIOCODE, UTF-8...) hex values if you try this with other text editors .

SO what i'm suggesting is to add a spaicel keyword that tell FASM to translate this specific (UNIOCODE, UTF-8...) characters into eASCII hex valuesonly when compiling. so FASM can handle properly this specific characters.

*eascii stands for extended ascii.

Last edited by EladAshkcenazi335 on 26 Jun 2017, 14:44; edited 3 times in total
Post 26 Jun 2017, 05:22
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Joined: 25 Jun 2017
Posts: 2
This video explalains why this weird bug even exists in the first place

https://www.youtube.com/watch?v=qBex3IDaUbU - more specifically explains the bug .

In short , you can't represent real eASCII characters in non eASCII forms like ANSI, UNIOCODE, UTF-8...
Because eASCII characters requires bit 7 to be set which is also the bit that UTF-8 uses to know if charcter is one byte long (non extended ascii) or two bytes long (or even longer) thus eASCII characters cannot represent with their real hex values and FASM is putting wrong values when using eASCII characters (their ANSI,UNICODE,UTF-8... forms ) instead of the real hex values.

I'm basically suggesting to use a spaicel keyword to tell FASM to compile this fake eASCII characters into real eASCII hex values (only when the keyword is used , otherwise to use the defualt behavior).

For Example :

the eASCII character has a (eASCII) hex value of 0xB2 but in (_) encoded text FASM will compile the following as:

mov al,'▓' =

mov al,(UTF-8 ) 0x9396E2 ; because this value is greater than 0xff (maximum value in a byte ), fasm will indicate an error!! (try if you don't belive me ), even though the user probably intended to use the eASCII hex value instead of the UTF-8 one.

mov al,(UTF-16) 0x2593 ; also an error will occur

mov al,(UTF-32) 0x00002593 ;same


BUT with the keyword FASM will theoretically compile the original 0xB2 value. (mov al,0xB2)

Post 26 Jun 2017, 06:55
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Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8028
Location: Kraków, Poland
Tomasz Grysztar
fasm is generally encoding-neutral, hence the strings of bytes are copied literally from the source text into output. If you need to convert between different encodings, the right way to do it is with macros, just like the "du" encoding macros that come as includes in fasm for Windows package.
Post 29 Jun 2017, 14:18
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