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Index > Compiler Internals > bug report: dd has potential to delete unrelated labels

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BAiC



Joined: 22 Mar 2011
Posts: 272
Location: California
BAiC
while increasing the usability of a macro I discovered that "dd" appears to delete (or block from creation) random labels. The code I'll upload was tested on the current version (1.70.03) as of today. here is a piece of the code:

line:411 of PsuedoInstructions.asm:
Code:
if lab < 8
        
        mov eax, dst
        db 0xB8+lab;mov eax
        dd dst ;       , label
        
        ali 2,8
        db 0xFF  ;cal
        db 0xD0+lab;    rax
        
    else
    
        db 0x41
        db 0xB8+(lab and 7);mov eax
        dd dst ;       , label
        
        ali 3,8
        db 0x41
        db 0xFF  ;cal
        db 0xD0+(lab and 7);    rax
        
end if    
removal of the "dd dst" causes the compile to succeed (though the code won't execute properly). for my particular situation I have a workaround (modifying the output of "mov eax, dst" using load/store).


Description: this is the current working version (includes workaround)
Download
Filename: Mathis2012July3.zip
Filesize: 410.68 KB
Downloaded: 262 Time(s)

Description: this fails to compile due to a "missing" label.
Download
Filename: Mathis_dd_problem.zip
Filesize: 384.23 KB
Downloaded: 236 Time(s)

Post 04 Jul 2012, 01:44
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17280
Location: In your JS exploiting you and your system
revolution
The problem is here:
Code:
    struc  ORB.Instigate 
    {
        ORB.Fx.Header .
        dd ORB.Instigate; last link.    
You are redefining 'dd' as a structure.
Post 04 Jul 2012, 02:12
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17280
Location: In your JS exploiting you and your system
revolution
There are some things to take note of with structures and macros:
Code:
mac1=3
mac2=4

macro mac1 [x] {display '1'}
struc mac2 [x] {.#z: display '2'}

mac1 mac2 ;displays '1'

dd mac1   ;generates a dword in the output file
dd mac2 ;displays '2'    
Notice that dd has now been interpreted as a structure label in the final line above.

But note the difference in how the order of definitions changes things:
Code:
macro mac1 [x] {display '1'}
struc mac2 [x] {.#z: display '2'}

mac1=3             ;displays '1'
mac2=4               ;defines mac2 as value of 4. The structure above still exists

mac1 mac2  ;displays '1'

;dd mac1 ;error: undefined symbol 'mac1'
dd mac2                ;displays '2'

if 4=mac2        ;check the value of 4
 display '3' ;displays '3', the comparison is true
end if

if mac2=22     ;displays '2', this is a structure definition for 'if'
 display '4'    ;displays '4' because the 'if' is not a executed
;end if         ;error: unexpected instruction    
Post 04 Jul 2012, 07:30
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