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List:       kde-bugs-dist
Subject:    [Bug 243234] ptrcheck doesnt handle sscanf properly
From:       <plasmahh () gmx ! net>
Date:       2010-06-30 9:50:24
Message-ID: 20100630095024.DB41947B26 () immanuel ! kde ! org
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https://bugs.kde.org/show_bug.cgi?id=243234


plasmahh@gmx.net changed:

           What    |Removed                     |Added
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                 CC|                            |plasmahh@gmx.net




--- Comment #2 from  <plasmahh gmx net>  2010-06-30 11:50:16 ---
I have not really looked at the sscanf implementation (and my doctor says I
should not as it won't be good for my heart), but if the pointer jumps from one
arg to the other, shouldn't ptrcheck somehow get that it has been
re-initialized from a new input parameter then? I would understand perfectly
the message if this internal pointer somehow managed to derive from buf0 a ptr
that is then suddenly pointing into buf1, buf if that ptr is really *set* to
point to buf1 -- the parameter to sscanf -- shouldn't ptrcheck see that as not
being derived from the previos buf0 pointer, but set to something from
"outside"?

if an implementation would do 

int x = param2 - param1;
char* ptr = param1;
/* use ptr */
ptr += x;
/* use it again*/

then I would say the complaint is correct, buf if it does

char* ptr = param1;
/* use ptr */
char* ptr = param2;

imho ptrcheck should be able to detect it.


Now that I think of it, the almost 100 suppressions that I wrote for our
software seem to be of a similar kind. We have a ptr variable that is always
re-used for pointing to an element determine within the looping.

It would really be nice if there could be a fix for this since it is a really
tedious thing to always write suppressions, since for every new case you have
to determine whether it is not maybe a bug, and with our old legacy code here
we find quite some bugs with ptrcheck that no other tool shows us...

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