Seg fault even though address space is accessible

[Ajay]

Hi All,

I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

However if I am able successfully access the structure using the
address from the gdb output
after it seg faulted. Output from gdb also give below.

Any idea y this is happening?
yes I am trying to access the structure element from where it seg
faulted.

I am surely missing something.
Any help is appreciated!

Thanks,
Ajay.

$$$$$$$$$$$$$ SEG FAULT $$$$$$$$$$$$$$$ $$

Program received signal SIGSEGV, Segmentation fault.
checkBFVectorLi st (BFVecList=0x84 187a0, BFlen=699)
at compute_sticky_ IP_per_ASN.c:77 6
776 vector = vector->nextVector;

$$$$$$$$$$$$$$$ $ BT $$$$$$$$$$$$$$$ $$$$$

(gdb) bt
#0 checkBFVectorLi st (BFVecList=0x84 187a0, BFlen=699)
at compute_sticky_ IP_per_ASN.c:77 6
#1 0x08051bb3 in buildPeerDetail StructFromLine (line=0x8418dd0 "566",
peerStruct=0x80 47124) at compute_sticky_ IP_per_ASN.c:75 2
#2 0x080522c1 in main (argc=11, argv=0x8047348)
at compute_sticky_ IP_per_ASN.c:17 9

$$$$$$$$$$$$$$$ $$$$$ ACCESSING STRUCTURE $$$$$$$$$$$$$$$ $$$$

(gdb) p *(bitfieldItemS truct *) 0x84187a0
$1 = {BFVector = 3309413121, nextVector = 0x84187b0}
(gdb) p ((bitfieldItemS truct *) 0x84187a0)->nextVector
$2 = (struct bitfieldItem *) 0x84187b0
(gdb) p ((struct bitfieldItem *) 0x84187a0)->nextVector
$3 = (struct bitfieldItem *) 0x84187b0

[Ike Naar]

In article <5e************ *************** *******@d1g2000 hsg.googlegroup s.com>,
Ajay <aj***********@ gmail.comwrote:

>{
bitfieldItemStr uct *BFVecHead, *currBFVec, *tmpBFVec;
[snip]
BFVecHead = (bitfieldItemSt ruct *) calloc(1,
sizeof(bitfiel dItemStruct *));

This looks suspicious.
You allocate room for one pointer instead of room for one struct.
Also, the cast is unnecessary.

Regards,
Ike

[Ajay]

On Jul 29, 8:22*pm, Ben Bacarisse <ben.use...@bsb .me.ukwrote:

Ajay <ajay.todim...@ gmail.comwrites :

Thanks for your replay!
I was using malloc but after the error appeared, I tried using calloc.
I changed back the code to using malloc.
The Seg. fault error still persists.
The new code is posted below:

Are you sure you are posting code you have compiled?

int
checkBFVectorLi st(bitfieldItem Struct **BFVecList, unsigned int BFlen)
int
buildBFVectorLi st(char *BFStr, bitfieldItemStr uct **BFVecList)

elsewhere you posted:

| main()
| {
| * ****
| *buildBFVectorL ist(currPeerDet ailItem->bitfieldStr,
| &(currPeerDetai lItem->bitfieldVector ));
| *checkBFVectorL ist(currPeerDet ailItem->bitfieldVector ,
| currPeerDetailI tem->bitfieldLength );
|
| ****
|
| }

The types here do not match up -- the compiler should reject it.

--
Ben.

Yes, you are right. The compiler did gave warning which I did not
notice.

Thanks a lot!
-Ajay.

[Martin Ambuhl]

Ajay wrote:

I am posting the code here.

What you posted isn't anywhere close to compilable.
I started trying to turn this mess into something that I could address,
but gave up.
That means it cannot possibly exhibit the problem you claim.
Please try again, and actually try compiling it and checking to see if
it exhibits the problem before posting.

[Antoninus Twink]

On 29 Jul 2008 at 22:29, Richard Heathfield wrote:

Ajay said:

>I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

There's a guy around here somewhere who can debug your problem (no matter
what it is) using only the debugger. Impressive. But if by some strange
chance he doesn't have time to answer your question, you'll have to rely
on the rest of us, and I'm afraid we tend to need to see the source code.

Yes Heathfield, very amusing, how we all admire your cleverness and wit.

Fact is, *noone* has claimed to be able to debug code using only a
debugger and not seeing the source code. *You* on the other hand (and
many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger. I call bullshit on that.

[Richard]

Antoninus Twink <no****@nospam. invalidwrites:

On 29 Jul 2008 at 22:29, Richard Heathfield wrote:

>Ajay said:

>>I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

There's a guy around here somewhere who can debug your problem (no matter
what it is) using only the debugger. Impressive. But if by some strange
chance he doesn't have time to answer your question, you'll have to rely
on the rest of us, and I'm afraid we tend to need to see the source code.

Yes Heathfield, very amusing, how we all admire your cleverness and
wit.

He really is an arrogant twit.

>
Fact is, *noone* has claimed to be able to debug code using only a
debugger and not seeing the source code. *You* on the other hand (and

Exactly.

many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger. I call bullshit on that.

Me too. Now cue one of his sycophantic friends to quote Kernighan or
somesuch telling us how much more difficult it is to debug a system than to
program it correctly the first time. Sigh.

[Flash Gordon]

Richard wrote, On 30/07/08 19:18:

Antoninus Twink <no****@nospam. invalidwrites:

>On 29 Jul 2008 at 22:29, Richard Heathfield wrote:

>>Ajay said:
I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

<snip>

>many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger. I call bullshit on that.

Me too. Now cue one of his sycophantic friends to quote Kernighan or
somesuch telling us how much more difficult it is to debug a system than to
program it correctly the first time. Sigh.

Obviously the person who managed to identify the bugs from just a couple
of snippets in this thread really managed to get hold of the entire
source without the rest of us seeing it.
--
Flash Gordon
Yes, I know, I should not reply to trolls.

[Richard]

Flash Gordon <sp**@flash-gordon.me.ukwri tes:

Richard wrote, On 30/07/08 19:18:

>Antoninus Twink <no****@nospam. invalidwrites:

>>On 29 Jul 2008 at 22:29, Richard Heathfield wrote:
Ajay said:
I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

<snip>

>>many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger. I call bullshit on that.

Me too. Now cue one of his sycophantic friends to quote Kernighan or
somesuch telling us how much more difficult it is to debug a system than to
program it correctly the first time. Sigh.

Obviously the person who managed to identify the bugs from just a
couple of snippets in this thread really managed to get hold of the
entire source without the rest of us seeing it.

I'm not sure what your point is. This is usenet. The code needed was
small. It in no way invalidates the benefits a debugger brings. Or in
this case paying attention to compiler warnings. of course some people
pulled the "can't compile it so cant help" line. others read the
code. Which was not insurmountable since it was about 20 lines.

[Chris Dollin]

Antoninus Twink wrote:

On 29 Jul 2008 at 22:29, Richard Heathfield wrote:

>Ajay said:

>>I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

There's a guy around here somewhere who can debug your problem (no matter
what it is) using only the debugger. Impressive. But if by some strange
chance he doesn't have time to answer your question, you'll have to rely
on the rest of us, and I'm afraid we tend to need to see the source code.

Yes Heathfield, very amusing, how we all admire your cleverness and wit.

Fact is, *noone* has claimed to be able to debug code using only a
debugger and not seeing the source code. *You* on the other hand (and
many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger.

Cite three instances that fit this claim.

--
'It changed the future .. and it changed us.' /Babylon 5/

Hewlett-Packard Limited registered office: Cain Road, Bracknell,
registered no: 690597 England Berks RG12 1HN

[Richard Heathfield]

Chris Dollin said:

Antoninus Twink wrote:

>On 29 Jul 2008 at 22:29, Richard Heathfield wrote:

>>Ajay said:
I got a segmentation fault while accessing a structure element.
I pasted the output from gdb and the backtrace.

There's a guy around here somewhere who can debug your problem (no
matter what it is) using only the debugger. Impressive. But if by some
strange chance he doesn't have time to answer your question, you'll
have to rely on the rest of us, and I'm afraid we tend to need to see
the source code.

Yes Heathfield, very amusing, how we all admire your cleverness and wit.

Fact is, *noone* has claimed to be able to debug code using only a
debugger and not seeing the source code. *You* on the other hand (and
many of your lackeys and lickspittles) have claimed on many occasions
that you can debug any problem using only a printout of the source code
and never a debugger.

Cite three instances that fit this claim.

Well, he can't, Chris, can he? The best he can do is quote himself or some
other troll pretending that I made such a claim.

Incidentally, I find it very strange that the trolls have no objection to
extending other people's positions, but don't like their own positions to
be extended.

Yes, I did extend the position held by one of the trolls that the debugger
is an essential tool - I forget whether it's Twink or Noname - to the
position that it *suffices* in all cases, and source code is never
required, which I think we can all agree is an untenable proposition. Of
course, this would have been dishonest, had I not pointed out what I had
done in that very same article.

Conclusions:

(1) our resident trolls either can't or won't read an entire article for
comprehension;
(2) they don't like being trolled;
(3) they can't grasp simple facts;
(4) they can't reason very well.

It's just as well I have them killfiled, really, or I'd waste huge amounts
of time arguing with them. I know they don't believe I've killfiled them,
but that's just another demonstration of (3).

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Keith Thompson]

Chris Dollin <ch**********@h p.comwrites:

Antoninus Twink wrote:

[more of the same]

Cite three instances that fit this claim.

Chris, why on Earth would you ask a troll to post *more* crap?

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"