[SOLVED] BUG: glibc detected *** listing: double free

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buzzkill

Joined: 15 Mar 2009
Posts: 111
Location: the nether lands

buzzkill

This is my first bug report for fasm, so I'm not quite sure where to put it; I experienced the bug under linux, so I'm putting it in the Linux forum, but I don't know if it's a linux-only bug...

I've got this really awesome app: Smile

Code:

format ELF

section '.text' executable

public _start
_start:
      mov   eax, 4      ; write
      mov   ebx, 1
      mov   ecx, msg
      mov   edx, msg.len
      int   80h         ; exit
      mov   eax, 1
      mov   ebx, 0
      int   80h

section '.data' writeable

msg         db "Hello, World!", 0Ah
.len        = $-msg

I assemble it and let fasm generate debug info:

Code:

$ fasm hello.asm hello.o -s hello.fas

I then want to generate a listing from the debug info (I run this command immediately after the fasm command, as recommended in the readme):

Code:

$ listing -a hello.fas hello.lst
*** glibc detected *** listing: double free or corruption (out): 0x0804ea48 ***
Aborted

Looks like some sort of malloc()-bug?

However, when I run the listing program without the -a switch, it does work without errors. But in the tools/readme.txt it says the -a switch is recommended, and besides: recommended or no, it should work, right? Smile

BTW, Tomasz (I assume you'll handle this), I compiled my listing executable with gcc, the way you recommend Smile

Let me know if there's more info I can give that's useful to you...

Last edited by buzzkill on 17 Mar 2009, 15:27; edited 1 time in total

17 Mar 2009, 14:48

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7725
Location: Kraków, Poland

Tomasz Grysztar

You're right, it's an memory allocation bug, just a little too short buffer is being allocated there.

For a quick fix, find this piece of code in LISTING.INC:

Code:

        mov     eax,[code_bytes_per_line]
        imul    eax,3
        add     eax,[maximum_address_length]
        add     eax,10
        call    alloc
        jc      not_enough_memory
        mov     [output_buffer],eax

And replace "add eax,10" with "add eax,12".

And, as you can see, this bug isn't specific just to Linux. Thanks for the report.

17 Mar 2009, 15:16

buzzkill

Joined: 15 Mar 2009
Posts: 111
Location: the nether lands

buzzkill

Wow, that has to be the quickest bug-fix I've ever seen Shocked

(As opposed to some other projects where bugs sit in a bugzilla for years...) And -ofcourse- your fix works like a charm, I just tested it. Thanks man, great work!

17 Mar 2009, 15:26

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid

Quote:

And replace "add eax,10" with "add eax,12".

Needless to say, but that's the result of using notebook instead of symbolic names for structures Wink

17 Mar 2009, 23:40

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7725
Location: Kraków, Poland

Tomasz Grysztar

vid wrote:

Needless to say, but that's the result of using notebook instead of symbolic names for structures

That's just the result of not couting all the spaces correctly in the fully-qualified listing line. In fact, I just realized that I still didn't take all of them into consideration, because with other count of byte columns you might still get more additional spaces for 8 columns alignment. It safer to put "add eax,18" there.

18 Mar 2009, 09:20

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