id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc	mlocked
11318	Segfault in mythbackend (mainserver/autoexpire?)	verycoldpenguin@…	stuartm	"I am experiencing a segfault in mythbackend, compiled on Centos 6.3 from master, using QT 4.8.4 (also present on QT 4.8.3). The setup is non-standard, but I believe that this is a generic issue (possibly being hit by the fact the system is an edge case). 
Symptoms are a segfault, when the system is relatively idle. I originally thought that it was triggered shortly after a recording finished, but, after furthther testing this has not been the case. I have not yet been able to trigger the fault at will. It is generally repeatable, usually between 1-6 hours, I don't think that it has been over 48 hours to trigger since I started looking for it.
Here is a snippet of code from mainserver.cpp which I believe is the fault. To me, it would seem that the incrementation of 'it' in the section is not needed, and could be the cause. But, I don't see why this isn't hitting more people if it is. This is starting at line 4667:
-----

{{{
void MainServer::GetFilesystemInfos(QList<FileSystemInfo> &fsInfos)
{
    QStringList strlist;
    FileSystemInfo fsInfo;

    fsInfos.clear();

    BackendQueryDiskSpace(strlist, false, true);

    QStringList::const_iterator it = strlist.begin();
    while (it != strlist.end())
    {
        fsInfo.setHostname(*(it++));
        fsInfo.setPath(*(it++));
        fsInfo.setLocal((*(it++)).toInt() > 0);
        fsInfo.setFSysID(-1);
        ++it;
        fsInfo.setGroupID((*(it++)).toInt());
        fsInfo.setBlockSize((*(it++)).toInt());
        fsInfo.setTotalSpace((*(it++)).toLongLong());
        fsInfo.setUsedSpace((*(it++)).toLongLong());
        fsInfo.setWeight(0);
        fsInfos.push_back(fsInfo);
    }
}}}

-----
Snippet from backtrace (full crash attached). Sorry but the line number changed (it is the one immediately after the '++it;') in the current head.
-----

{{{
Thread 19 (Thread 0x7fffcebfd700 (LWP 15361)):
#0  0x00007fffef24ae74 in QLocalePrivate::stringToLongLong(QString const&, int, bool*, QLocalePrivate::GroupSeparatorMode) const () from /usr/local/Trolltech/Qt-4.8.4/lib/libQtCore.so.4
No symbol table info available.
#1  0x00007fffef27219c in QString::toLongLong(bool*, int) const () from /usr/local/Trolltech/Qt-4.8.4/lib/libQtCore.so.4
No symbol table info available.
#2  0x00007fffef272239 in QString::toInt(bool*, int) const () from /usr/local/Trolltech/Qt-4.8.4/lib/libQtCore.so.4
No symbol table info available.
#3  0x00000000004948f5 in MainServer::GetFilesystemInfos (this=0x89f140, fsInfos=...) at mainserver.cpp:4662
        strlist = {<QList<QString>> = {{p = {static shared_null = {ref = {_q_value = 604}, alloc = 0, begin = 0, end = 0, sharable = 1, array = {0x0}}, d = 0x7fffa4050520}, d = 0x7fffa4050520}}, <No data fields>}
        __FUNCTION__ = ""GetFilesystemInfos""
        fsInfo = {<QObject> = {<No data fields>},
}}}

-----

Both my begin and end are 0, I think that the while line should possibly be changed from:
while (it != strlist.end())
to:
while (it < strlist.end())
And possibly the 'it++;' removed. I don't think that the code should have been run anyway though (given that begin and end should both return 0, or the same pointer).
"	Bug Report - Crash	closed	blocker	0.27	MythTV - General	Master Head	medium	fixed			0