[fasmg] segfault (iteration too high + no enough memory)

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MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 11 Nov 2019, 13:07

Hello! With this code:

Code:

_sections? := $00
namespace _sections?
end namespace
macro section? name?*
        local present
        present = $00
        irpv it, _sections?._name?
                if (name = it)
                        present = $01
                        break
                end if
        end irpv
        if (~(present))
                namespace _sections?
                        _name? =: name
                end namespace
        end if
end macro
repeat $DEED, i:$00
        section (`i)
end repeat

fasmg double free on linux sometime and segfault on UNIX(FreeBSD). I've not tested yet on Window/DOS.
Hope this help Smile

11 Nov 2019, 13:07

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8353
Location: Kraków, Poland

Tomasz Grysztar 11 Nov 2019, 15:07

Thank you for the report! I found a pointer corruption bug in IRPV handler. I minimized your sample to expose it:

Code:

repeat $DEED
        x =: '1'
end repeat

irpv it, x
       db it
end irpv

Please try version "iqi5k", it fixes this bug in specific.

11 Nov 2019, 15:07

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8353
Location: Kraków, Poland

Tomasz Grysztar 11 Nov 2019, 15:17

Back to your original snippet - such linear search is definitely a sub-optimal method of looking for an existing definition.

A trick I could recommend is to convert the string that contains section name into something that can be used as a label name in fasmg, and then you can make fasmg look up whether such name has been declared already. For example, you can simply convert any string to a decimal number and then use this number as a label name:

Code:

_sections? := $00
namespace _sections?
end namespace
macro section? name?*
        local present
        present = $00
        repeat 1, d:name
                if definite _sections.d
                        present = $01
                else
                        _sections.d := name
                end if
        end repeat
end macro
repeat $DEED, i:$00
        section (`i)
end repeat

11 Nov 2019, 15:17

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 11 Nov 2019, 19:51

You're welcome. I like the idea of contributing to fasmg Smile

. Thx for the tips too. In fact my whole code with 100+ sections was very slow (0.5 sec).
The problem is that, I record not only the section name but also the origin, alignement,... So for retreive the original value in a postpone block I do an irpv break for each field.
But I guess now, I can speed up the whole things Smile

11 Nov 2019, 19:51

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 14 Nov 2019, 16:21

Hi! After some experiment, I think that I found another bug (segfault/abort) on Linux/Unix. This concern the use of "?" in front of an identifier in an irpv and an namespace block.

Code:

Magic? := $00
namespace Magic?
        ?$CAFE? := "JAVA"
end namespace
irpv item, Magic?.?$CAFE?
        display (`item), $0A ; segfault here
end irpv

Hope this might help Smile

Last edited by MaoKo on 15 Nov 2019, 02:13; edited 1 time in total

14 Nov 2019, 16:21

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8353
Location: Kraków, Poland

Tomasz Grysztar 14 Nov 2019, 16:51

The "?" in front of an identifier is a modifier of an entire identifier, it cannot be used in a middle of identifier like you did. The symbol that you defined has a case-insensitive name "$CAFE" and this is how you should access it:

Code:

irpv item, Magic?.$CAFE?

In addition to that, the value that IRPV gives to "item" parameter is a proxy, because the iterated value is not symbolic, but evaluated. Therefore "`item" is not useful to show this value, as it only sees the name of the proxy.

You can either display the value directly, assuming it is a string:

Code:

Magic? := $00
namespace Magic?
        ?$CAFE? := "JAVA"
end namespace
irpv item, Magic?.$CAFE?
        display item, $0A
end irpv

Or you can use symbolic assignment:

Code:

Magic? := $00
namespace Magic?
        ?$CAFE? equ "JAVA"
end namespace
irpv item, Magic?.$CAFE?
        display `item, $0A
end irpv

14 Nov 2019, 16:51

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 14 Nov 2019, 17:29

Thx Tomasz. I fact I knew for the "?", this was originally a typo that I made when writing some code.
However I thought that the proxy name "." only apply to negative value. But the whole code is just a proof of concept for the crash. Not in use in production obviously Smile

14 Nov 2019, 17:29

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 23 Nov 2019, 20:39

Tomasz? What going on with this segfault?

23 Nov 2019, 20:39

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8353
Location: Kraków, Poland

Tomasz Grysztar 23 Nov 2019, 21:27

Oh, I'm sorry, I completely forgot about it. Please try the "iqyjc" release.

23 Nov 2019, 21:27

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 23 Nov 2019, 21:54

Yes thx. Your are fast x).

23 Nov 2019, 21:54

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