228542 - Divide by zero bug in Universal charset detecter

Status: RESOLVED FIXED

(Core :: Internationalization, defect)

Description

[Vladimir]

User-Agent:       Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) Opera 7.23  [en]
Build Identifier: 

When text chunk have no latin chars we get divide by zero Error

In nsLatin1Prober.cpp Line 193 
    confidence = mFreqCounter[3]*1.0f / total;
    confidence -= mFreqCounter[1]*20.0f/total;

Must be replaced with 

  if(!total)
	confidence = 0.0f;
  else{
    confidence = mFreqCounter[3]*1.0f / total;
    confidence -= mFreqCounter[1]*20.0f/total;
  }

Reproducible: Always

Steps to Reproduce:
1.
2.
3.

Comment 1

[Simon Montagu :smontagu]

Is there a reproducible crash associated with this, or did you find the bug by
code inspection? I ask only out of curiosity, and I agree that we should fix
this anyway.

Comment 2

[Vladimir]

Yes and Yes.
I found it while debug universal detector as DLL on little amount of text.
Two bugs (In reply to comment #1)
> Is there a reproducible crash associated with this, or did you find the bug by
> code inspection? I ask only out of curiosity, and I agree that we should fix
> this anyway.
Yes and Yes.
I found it while debug universal detector as DLL on little amount of text.
Two bugs 228545 and 228542 are interrelated. 

Comment 3

[Vladimir]

Attachment: patch

Comment 4

[Vladimir]

Attachment: bug reproduction file

Due to bug 228542 if we have no english chars in file (text chuck)
total will be equal to 0 and confidence = mFreqCounter[3]*1.0f / total;
will crash detector or fill confidence with NaN

Comment 5

[Simon Montagu :smontagu]

Comment on attachment 151519 [details] [diff] [review]
patch

No need for a new patch this time, but in future please make your patches with
diff -pu9
r=smontagu

Comment 6

[Mike Kaply [:mkaply]]

Comment on attachment 151519 [details] [diff] [review]
patch

a=mkaply for 1.7.1

When this is checked in, please use consistent bracing on the if statement.

thanks

Comment 7

[timeless]

mozilla/extensions/universalchardet/src/nsLatin1Prober.cpp 	1.5  

Comment 8

[Hiro]

AVIARY_1_0_20040515_BRANCH does not checkin yet.

Comment 9

[timeless]

mozilla/extensions/universalchardet/src/nsLatin1Prober.cpp 	1.3.50.1

Comment 10

[Mike Cowperthwaite]

The patch appears to have been checked in, but this bug is still not marked 
FIXED -- any reason why?

Timeless?

Comment 11

[Vladimir]

Thanx for mention.