Bug 155651

Summary: segmentation fault using qt's QPtrList at() method
Product: [Fedora] Fedora Reporter: Adrian Reber <adrian>
Component: qtAssignee: Than Ngo <than>
Status: CLOSED NOTABUG QA Contact: Ben Levenson <benl>
Severity: medium Docs Contact:
Priority: medium    
Version: rawhide   
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2005-04-28 10:39:27 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Adrian Reber 2005-04-22 08:50:51 UTC 
Following code crashes with a segmentation fault:

#include <qstring.h>
#include <qptrlist.h>
class track_info {
  public:

    QString songname;
};

int main() {
        QPtrList < track_info > trk;
        QString test;
        trk.append(new track_info());
        QString *haha = new QString("haha");
        trk.at(1)->songname = haha->utf8();
        return 0;
}

I am using following command to compile it:
gcc qttest.cc  -I/usr/lib/qt-3.3/include -lqt-mt -L/usr/lib/qt-3.3/lib

And gdb says:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1208174912 (LWP 13456)]
0x07560177 in QString::setUnicode () from /usr/lib/qt-3.3/lib/libqt-mt.so.3
(gdb)

I think that this is a bug because the documentation
(http://doc.trolltech.com/3.3/qptrlist.html#at) says:

"Returns a pointer to the item at position index in the list, or 0 if the index
is out of range."

I have tested it with qt-3.3.4-0.fc3.0, qt-devel-3.3.3-8 and qt-3.3.4-11
Comment 1 Than Ngo 2005-04-28 10:39:27 UTC 
Hm, it seems your test case is broken, the index is out of range in this case
and get a NULL pointer here! it's why it crashes.
Comment 2 Adrian Reber 2005-04-28 11:19:49 UTC 
Okay, then I have maybe misunderstood the documentation:

"Returns a pointer to the item at position index in the list, or 0 if the index
is out of range."

I thought it means I get the element at position 0 but maybe it means I get
NULL. If that's the case then it is my fault.