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Bug 105784 - Compiling kde/qt from CVS hangs on QValueList
Compiling kde/qt from CVS hangs on QValueList
Product: Fedora
Classification: Fedora
Component: gcc (Show other bugs)
i686 Linux
medium Severity high
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Assigned To: Ngo Than
Ben Levenson
Depends On:
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Reported: 2003-09-27 10:31 EDT by Koos
Modified: 2007-11-30 17:10 EST (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Clone Of:
Last Closed: 2003-10-02 05:48:36 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Koos 2003-09-27 10:31:30 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (compatible; Konqueror/3.1; Linux)

Description of problem:
Hi, I tried compiling CVS HEAD for kde, but Qt (from qt-copy) already fails running designer. I made a small test case of an hang I found:
#include <iostream>
#include <qvaluelist.h>

struct Data { int x; };

int main(int argc, char**) {
    QValueList<Data> mylist;
    Data data;
    QValueList<Data>::iterator it = mylist.append(data);
    (*it).x = (argc > 1 ? argc : 0);
    std::cout << (*it).x << std::endl;

g++ -O2 myvaluelist.cpp -o myvaluelist -I$QTDIR/include -L$QTDIR/lib -lqt-mt
This little program works w/o arguments, but hangs w/ an arg.
W/o -O2, it works.
(installation is severn from 25 sept, gcc-3.3.1-5)

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. compile and run the above

Additional info:
Comment 1 Paul Nasrat 2003-09-27 10:36:47 EDT
I replicated this on Fedora Core beta 2 by just compiling the above sample.

gdb seemed to indicate it was hanging at line 110 of qvaluelist.h:

    T& operator*() { return node->data; }
Comment 2 Ngo Than 2003-09-29 09:48:23 EDT
Hmm, it's beta software, which Red Hat doses not support. Please report this bug
to trolltech or kde developers. Please tell them which gcc version you use. Thanks
Comment 3 Koos 2003-09-29 09:57:42 EDT
Imo it's a gcc optimization bug.  
  (*it).x = (argc > 1 ? argc : 0) 
It hang if it assigns the if part (argc) and not if it assign the else part (0). How can that be Qt 
Btw, Paul Nasrat suggest it's reproducable with the severn's include Qt. 
Comment 4 Koos 2003-09-29 13:41:58 EDT
Ok, made another testcase without qt this time, maybe that helps.. 
#include <iostream> 
struct Data { int x; }; 
template <class T> 
struct Wrapper { 
    Wrapper(Data & d) : data (d) {} 
    Data & operator * () { return data; } 
    Data & data; 
int main(int argc, char**) { 
    Data data; 
    Wrapper<Data> mywrapper(data); 
    (*mywrapper).x = (argc > 1 ? argc : 0); 
    std::cout << (*mywrapper).x << std::endl; 
Compile as 'g++ myvaluelist.cpp -o myvaluelist  -O2' and it hangs if run with an 
I've compiled it also with gcc-3.3.1 on an old RH-7.1 system: 
$ gcc -v 
Reading specs from /usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.1/specs 
Configured with: ../gcc-3.3.1/configure --prefix=/usr --infodir=/usr/share/info 
--mandir=/usr/share/man --enable-shared --enable-threads --disable-nls : 
(reconfigured) ../gcc-3.3.1/configure --prefix=/usr --infodir=/usr/share/info --mandir=/
usr/share/man --enable-shared --enable-threads --disable-nls 
Thread model: posix 
gcc version 3.3.1 
And there isn't a hang. 
Comment 5 Koos 2003-09-29 17:31:48 EDT
Hmm, I got this hang reproduced so soon, that I forgot to reread the code :). 
Apprently it has nothing to do with templates but with operator *() returning a 
#include <iostream> 
struct Data { int x; }; 
struct Wrapper { 
    Wrapper() {} 
    Data & operator * () { return data; } 
    Data data; 
int main(int argc, char**) { 
    Wrapper mywrapper; 
    (*mywrapper).x = (argc > 1 ? argc : 0); 
    std::cout << (*mywrapper).x << std::endl; 
Comment 8 Ngo Than 2003-10-02 05:48:36 EDT
it's now fixed in gcc-3.3.1-6, which will be available in rawhide soon. Thanks
for your report.

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