Date: Fri, 15 Apr 2016 14:39:21 +0930 From: Shane Ambler <FreeBSD@ShaneWare.Biz> To: Dimitry Andric <dim@FreeBSD.org> Cc: FreeBSD-ports <freebsd-ports@freebsd.org> Subject: Re: Need some help with c++/qt5 code Message-ID: <57107781.7040102@ShaneWare.Biz> In-Reply-To: <CC7B253B-DE3B-4049-96D8-A06DB52A0346@FreeBSD.org> References: <570F85E3.6060000@ShaneWare.Biz> <CC7B253B-DE3B-4049-96D8-A06DB52A0346@FreeBSD.org>
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On 15/04/2016 08:02, Dimitry Andric wrote:
> On 14 Apr 2016, at 13:58, Shane Ambler <FreeBSD@ShaneWare.Biz> wrote:
>>
>> Hi there, while I am comfortable with c and python, I only know a little
>> c++ and could use some help.
> ...
>> class TPanelFactory
>> {
>> QString m_panelType;
>> static QMap<QString, TPanelFactory *> m_table;
>>
>> public:
>> TPanelFactory(QString panelType);
>> ~TPanelFactory();
>>
>> QString getPanelType() const { return m_panelType; }
>>
>> virtual void initialize(TPanel *panel) = 0;
>> virtual TPanel *createPanel(QWidget *parent);
>> static TPanel *createPanel(QWidget *parent, QString panelType);
>> };
>>
>> m_table is then in the source file as
>>
>> QMap<QString, TPanelFactory *> TPanelFactory::m_table;
>>
>> The segfault happens in the constructor -
>>
>> TPanelFactory::TPanelFactory(QString panelType)
>> : m_panelType(panelType)
>> {
>> assert(m_table.count(panelType) == 0);
>> m_table[m_panelType] = this;
>> }
>>
>> the last line causes the segfault, if I comment it out then main() is
>> entered, but I expect removing that line will bite back soon enough.
>>
>> How can I get this working?
>>
>> Why would this fail on FreeBSD but not OSX or windows?
>
> Most likely the program depends on the initialization order of global
> constructors. This is bad practice, and should be avoided.
>
> So what's the value of m_table at this point? It looks a lot like it
> is still uninitialized.
Yes uninitialised sounds right - what is the right way to fix this?
I get non-zero values for the address of each variable there, but while
they may be allocated I don't think they are initialised as a call to
m_table.count() will cause a segfault.
TPanelFactory::TPanelFactory(QString panelType)
: m_panelType(panelType)
{
assert(m_table.count(panelType) == 0);
std::cout << "m_table.count is " << m_table.count(panelType) <<
std::endl;
std::cout << "TPanelFactory::m_table is at " <<
&TPanelFactory::m_table << std::endl;
std::cout << "this is at " << this << std::endl;
std::cout << "panelType is at " << &panelType << std::endl;
std::cout << "m_panelType is at " << &m_panelType << std::endl;
m_table[m_panelType] = this;
}
The output with m_table.count() prevents the other output lines
running, without the m_table.count() line, the others can output
before the segfault.
Without the m_table.count() line -
% ./opentoonz
TPanelFactory::m_table is at 0xc39568
this is at 0xc3a628
panelType is at 0x7fffffffd408
m_panelType is at 0xc3a630
Segmentation fault
With the m_table.count() line -
% lldb opentoonz
Current executable set to 'opentoonz' (x86_64).
(lldb) run
Process 56499 launching
Process 56499 stopped
(lldb) Process 56499 launched:
'/home/shane/Projects/opentoonz/test_install/bin/opentoonz' (x86_64)
Process 56499 stopped
* (lldb) thread #1: tid = 101441, 0x00000000004f2d7f
opentoonz`QMapData<QString, TPanelFactory*>::nodeRange(QString const&,
QMapNode<QString, TPanelFactory*>**, QMapNode<QString,
TPanelFactory*>**) + 31, stop reason = invalid address (fault address: 0x10)
frame #0: 0x00000000004f2d7f opentoonz`QMapData<QString,
TPanelFactory*>::nodeRange(QString const&, QMapNode<QString,
TPanelFactory*>**, QMapNode<QString, TPanelFactory*>**) + 31
opentoonz`QMapData<QString, TPanelFactory*>::nodeRange(QString const&,
QMapNode<QString, TPanelFactory*>**, QMapNode<QString,
TPanelFactory*>**) + 31:
-> 0x4f2d7f: movq 0x10(%r14), %r15
0x4f2d83: addq $0x8, %r14
0x4f2d87: testq %r15, %r15
0x4f2d8a: je 0x4f2e6a ; QMapData<QString,
TPanelFactory*>::nodeRange(QString const&, QMapNode<QString,
TPanelFactory*>**, QMapNode<QString, TPanelFactory*>**) + 266
(lldb) bt
* thread #1: tid = 101441, 0x00000000004f2d7f
opentoonz`QMapData<QString, TPanelFactory*>::nodeRange(QString const&,
QMapNode<QString, TPanelFactory*>**, QMapNode<QString,
TPanelFactory*>**) + 31, stop reason = invalid address (fault address: 0x10)
* frame #0: 0x00000000004f2d7f opentoonz`QMapData<QString,
TPanelFactory*>::nodeRange(QString const&, QMapNode<QString,
TPanelFactory*>**, QMapNode<QString, TPanelFactory*>**) + 31
frame #1: 0x00000000004f20d8
opentoonz`TPanelFactory::TPanelFactory(QString) + 120
frame #2: 0x000000000057118d
opentoonz`XsheetViewerFactory::XsheetViewerFactory() + 45
frame #3: 0x00000000005701d7 opentoonz`_GLOBAL__I_a + 1687
frame #4: 0x000000000080a1b2 opentoonz`__do_global_ctors_aux + 34
frame #5: 0x000000000048551e opentoonz`_init + 14
frame #6: 0x0000000800c03c9f
frame #7: 0x0000000800c0328e
(lldb) quit
--
FreeBSD - the place to B...Software Developing
Shane Ambler
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