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Index > Compiler Internals > [bug][Solved in FASM 1.71.16] invalid ELF file generated

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JohnFound



Joined: 16 Jun 2003
Posts: 3502
Location: Bulgaria
JohnFound
Hi, Tomasz.

It is very old problem, that I get from time to time invalid ELF file generated.

The sources where this happened were pretty big and it was impossible to search the reasons for such strange behavior.

Fortunately, today I managed to construct very small source, where the bug appears and can be reproduced. The example is artificial and does not compile to valid program:
Code:
        format ELF executable 3
        entry start

        segment readable writeable executable
start:
        int3

        align 4   ; comment this line in order to get valid elf.
        rb  16

        segment interpreter readable
        db '******************', 0

        segment dynamic readable
        db 8 dup('.')

        segment readable writeable
        db 8 dup '?'    


The source is compiled to ELF file with size 197 bytes, where the asterisk string '******************',0 misses at all.

After commenting out the 'align 4' directive, the source compiles to ELF file with size 216 bytes (!) where the mentioned string exists.

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Tox ID: 48C0321ADDB2FE5F644BB5E3D58B0D58C35E5BCBC81D7CD333633FEDF1047914A534256478D9


Last edited by JohnFound on 30 Oct 2013, 12:46; edited 2 times in total
Post 29 Oct 2013, 21:41
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HaHaAnonymous



Joined: 02 Dec 2012
Posts: 1180
Location: Unknown
HaHaAnonymous
[ Post removed by author. ]


Last edited by HaHaAnonymous on 28 Feb 2015, 19:15; edited 1 time in total
Post 29 Oct 2013, 22:24
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17332
Location: In your JS exploiting you and your system
revolution
Confirmed. I made it sticky.
Post 30 Oct 2013, 01:27
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7734
Location: Kraków, Poland
Tomasz Grysztar
While testing the fix for this problem I have also found another bug - one that made the addresses to be generated incorrectly if you used the default segment (that is: start code right away after "format ELF executable", without a segment directive). I fixed them both. Please try 1.71.16.
Post 30 Oct 2013, 11:26
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JohnFound



Joined: 16 Jun 2003
Posts: 3502
Location: Bulgaria
JohnFound
Everything seems to be OK now. Two bugs less in FASM - one more step towards the perfect assembler. Smile
Post 30 Oct 2013, 12:18
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HaHaAnonymous



Joined: 02 Dec 2012
Posts: 1180
Location: Unknown
HaHaAnonymous
[ Post removed by author. ]


Last edited by HaHaAnonymous on 28 Feb 2015, 19:14; edited 1 time in total
Post 30 Oct 2013, 15:00
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17332
Location: In your JS exploiting you and your system
revolution
HaHaAnonymous wrote:
Humans will never meet perfection.
That depends upon how you define perfection.
Post 30 Oct 2013, 15:05
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