Yes, the [`QObject::~QObject`][1] destructor takes care of that:

&gt; All signals to and from the object are automatically disconnected, and any pending posted events for the object are removed from the event queue.   
&gt; However, it is often safer to use [`deleteLater()`][2] rather than deleting a QObject subclass directly.

Do take care though:

&gt; **Warning:** Deleting a QObject while pending events are waiting to be delivered can cause a crash. You must not delete the QObject directly if it exists in a different thread than the one currently executing. Use deleteLater() instead, which will cause the event loop to delete the object after all pending events have been delivered to it.

[1]: http://qt-project.org/doc/qt-4.8/qobject.html#dtor.QObject
[2]: http://qt-project.org/doc/qt-4.8/qobject.html#deleteLater

How can I get diff in file content of current and previous revision number by command line?

And how can I get previous revision number?

Command to get svn diff of current and previous revision number

I&#39;m trying to launch an `Intent` to open a pdf inside my assets folder in my app. I&#39;ve read dozens of posts but am still stuck. Apparently I need to copy the pdf to the sd card first then launch an `Intent`. It still doesn&#39;t work.

I think the problem is the `Intent` launching so I&#39;m simply trying to open a file &quot;example.pdf&quot; that I copied onto the SD card using this code:

    Log.w(&quot;IR&quot;, &quot;TRYING TO RENDER: &quot; + Environment.getExternalStorageDirectory().getAbsolutePath()+&quot;/example.pdf&quot;);
    Intent intent = new Intent(Intent.ACTION_VIEW);
    intent.setDataAndType(Uri.parse(Environment.getExternalStorageDirectory().getAbsolutePath()+&quot;/example.pdf&quot;), &quot;application/pdf&quot;);
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

    try {
        startActivity(intent);
        Log.e(&quot;IR&quot;, &quot;No exception&quot;);
    } 
    catch (ActivityNotFoundException e) {
       	Log.e(&quot;IR&quot;, &quot;error: &quot; + e.getMessage());
        Toast.makeText(InvestorRelations.this, 
            &quot;No Application Available to View PDF&quot;, 
            Toast.LENGTH_SHORT).show();
    }

This is my LogCat output.

    05-10 10:35:10.950: W/IR(4508): TRYING TO RENDER: /mnt/sdcard/example.pdf
    05-10 10:35:10.960: E/IR(4508): No exception
    
Except when this code is run, I get the following Toast (not produced by my app)

&quot;Not a supported document type&quot;

But I can open the document manually through the PDF viewing app installed. Any help would be hugely appreciated.

How to open a PDF via Intent from SD card

Does Qt automatically remove connections between objects , when one of the side is deleted ?

e.g `connect (A .. , B ..)` , when A (a pointer) is deleted , or B is deleted , will the connection be disconnected ? 

Is it necessary to use disconnect explicitly in destructor ?

Are signals in Qt automatically disconnected when one of the class is deleted

Does Qt automatically remove connections between objects , when one of the side is deleted ?
e.g <code>connect (A .. , B ..)</code> , when A (a pointer) is deleted , or B is deleted , will the connection be disconnected ?
Is it necessary to use disconnect explicitly in destructor ?

How to change the title of the window in Qt? (Both for `QDialog` and `QMainWindow`.)

How to change the Title of the window in Qt?

I have three files . The contents of main.cpp are


    #include&lt;iostream&gt;
    #include&lt;QString&gt;
    
    #include &quot;util.h&quot;
    
    int main()
    {
        using Util::convert2QString;
    
        using namespace std;
        int n =22;
        QString tmp = convert2QString&lt;int&gt;(n);
    
        return 0;
    }



util.h

    namespace Util
    {
        template&lt;class T&gt;
        QString convert2QString(T type , int digits=0);
    }


util.cpp


    namespace Util
    {
        template&lt;class T&gt;
            QString convert2QString(T type, int digits=0)
            {
                using std::string;
                
                string temp = (boost::format(&quot;%1%&quot;) % type).str();
    
                return QString::fromStdString(temp);
            }
    }

When I try to compile these files with following command I get undefined reference error

    vickey@tb:~/work/trash/template$ g++ main.cpp  util.cpp -lQtGui -lQtCore  -I. -I/usr/local/Trolltech/Qt-4.8.0/include/QtCore -I/usr/local/Trolltech/Qt-4.8.0/include/QtGui -I/usr/local/Trolltech/Qt-4.8.0/include
    /tmp/cca9oU6Q.o: In function `main&#39;:
    main.cpp:(.text+0x22): undefined reference to `QString Util::convert2QString&lt;int&gt;(int, int)&#39;
    collect2: ld returned 1 exit status

Is there something wrong with the template declaration or implementation ? why M I getting these linking errors :?


undefined reference to template function

I want to cross compile the Qt libraries (and eventually my application) for a Windows x86_64 target using a Linux x86_64 host machine. I feel like I am close, but I may have a fundamental misunderstanding of some parts of this process.

I began by installing all the mingw packages on my Fedora machine and then modifying the `win32-g++` qmake.conf file to fit my environment. However, I seem to be getting stuck with some seemingly obvious configure options for Qt: `-platform` and `-xplatform`. Qt documentation says that `-platform` should be the host machine architecture (where you are compiling) and `-xplatform` should be the target platform for which you wish to deploy. In my case, I set `-platform linux-g++-64` and `-xplatform linux-win32-g++` where linux-win32-g++ is my modified win32-g++ configuration.

My problem is that, after executing configure with these options, I see that it invokes my system&#39;s compiler instead of the cross compiler (x86_64-w64-mingw32-gcc). If I omit the `-xplatform` option and set `-platform` to my target spec (linux-win32-g++), it invokes the cross compiler but then errors when it finds some Unix related functions aren&#39;t defined.

Here is some output from my latest attempt: http://pastebin.com/QCpKSNev.

Questions:

 1. When cross-compiling something like Qt for Windows from a Linux host, should the native compiler *ever* be invoked? That is, during a cross compilation process, shouldn&#39;t we use *only* the cross compiler? I don&#39;t see why Qt&#39;s configure script tries to invoke my system&#39;s native compiler when I specify the `-xplatform` option.

 2. If I&#39;m using a mingw cross-compiler, when will I have to deal with a specs file? Spec files for GCC are still sort of a mystery to me, so I am wondering if some background here will help me.

 3. In general, beyond specifying a cross compiler in my qmake.conf, what else might I need to consider?


How do I configure Qt for cross-compilation from Linux to Windows target?

I have this function in my program that converts integers to strings:

        QString Stats_Manager::convertInt(int num)
        {
            stringstream ss;
            ss &lt;&lt; num;
            return ss.str();
        }

But when ever i run this i get the error:

    aggregate &#39;std::stringstream ss&#39; has incomplete type and cannot be defined

Im not really sure what that means. But if you know how to fix it or need any more code please just comment. Thanks.


Qt c++ aggregate &#39;std::stringstream ss&#39; has incomplete type and cannot be defined

I want to start a cross-platform project. I had my researches and now I am almost certain Qt is the right deal. There is a big obstacle here though: *licensing*.

I want to sell my project and I also don&#39;t want to give out any source related to my work or pay for a license. I checked and noticed Qt offers both commercial and open source solutions. I have heard too many conflicting sayings on Qt licensing which confused me a lot. Some say that even if I use LGPL version of Qt, I still need to submit my code. Is this true?

Can someone give me a simple explanation on Qt licenses and tell me if I can sell my application without any kind of restrictions at all or not? Would anyone tell me any other equivalents to Qt for cross-platform development without any restrictions?


Can I use Qt LGPL license and sell my application without any kind of restrictions?

As far as I know, I should destroy in destructors everything I created with `new` and close opened filestreams and other streams.
However, I have some doubts about other objects in C++:

- `std::vector` and `std::string`s: Are they destroyed automatically?

- If I have something like

        std::vector&lt;myClass*&gt; 

  of pointers to classes. What happens when the vector destructor is called?  
  Would it call automatically the destructor of `myClass`? Or only the vector is destroyed but all the Objects it contains are still existant in the memory?

- What happens if I have a pointer to another class inside a class, say:

        class A {
          ClassB* B;
        }

  and Class A is destroyed at some point in the code. Will Class B be destroyed too or just the pointer and class B will be still existent somewhere in the memory? 

C++ Destructors with Vectors, Pointers,

I have found it useful to use forward declaration of classes in combination with `std::unique_ptr` as in the code below. It compiles and works with GCC, but the whole thing seem kind of strange, and I wonder if this is standard behaviour (i.e. required by the standard)? Since B isn&#39;t a complete type when I declare the `unique_ptr`.

###A.hpp
    #include &lt;memory&gt;

    class B;

    class A {
        std::unique_ptr&lt;B&gt; myptr;
        // B::~B() can&#39;t be seen from here
    public:
        ~A();
    };

###A.cpp
    #include &quot;B.hpp&quot;
    //B.hpp has to be included, otherwise it doesn&#39;t work.

    A::~A() = default; // without this line, it won&#39;t compile 
    // however, any destructor definiton will do.

I suspect this has to do with the destructor (and therefore the need to call the destructor of `unique_ptr&lt;B&gt;`) is defined in a specific compilation unit (A.cpp).

Forward declaration with unique_ptr?

I am studying how garbage collector works in c#. I am confused over the use of `Destructor`, `Dispose` and `Finalize` methods. 

As per my research and understandings, having a Destructor method within my class will tell the garbage collector to perform the garbage collection in the way mentioned in the destructor method which cannot be called explicitly on the instances of the class. 

The `Dispose` method is meant to provide the user to control the garbage collection.  The `Finalize` method frees the resources used by the class, but not the object itself. 

I am not sure if I understand it the right way. Please clarify the doubts. Any further links or guides are welcome.


Difference between destructor, dispose and finalize method

**EDIT : Summary of answers**

In the following, B is a subclass of A.

It&#39;s a matter of terminology; ctors and dtors are **not** inherited, in the sense that the ctor/dtor of B will *not* be borrowed from A&#39;s interface. A class has at least one constructor, and has exactly one destructor.

 - **Constructors**: 
  - B does not inherit constructors from A;
  - Unless B&#39;s ctor explicitely calls *one of* A&#39;s ctor, the default ctor from A will be called automatically *before* B&#39;s ctor body (the idea being that A needs to be initialized before B gets created).
 - **Destructors**:
  - B does not inherit A&#39;s dtor;
  - *After* it exits, B&#39;s destructor will automatically call A&#39;s destructor.


*Acknowledgements:*
I would like to thank especially Oli Charlesworth and Kos for their answers, I set Kos&#39; answer as the solution because it was the one I understood best.

----------

**ORIGINAL POST**

When you search for &quot;C++ destructor inheritance site:stackoverflow.com&quot; on Google, you currently find the following posts:

 1.  https://stackoverflow.com/questions/8103805/constructor-and-destructor-inheritance: two users with 30k+ reputation say that it is inherited, and that it&#39;s not
 2.  https://stackoverflow.com/questions/2198379/are-virtual-destructors-inherited: here nothing is mentioned that would point to destructors not being inherited
 3.  https://stackoverflow.com/questions/6856488/destructors-and-inheritance-in-c: The comments seem to indicate the destructors are inherited

**Q1:** What I also know from practice, is that you cannot initialize a derived object with the same prototype than it&#39;s parent constructor without explicitely defining a constructor for the derived class, is that correct?


----------


Even though it&#39;s rather clear from the posts that destructors seem to be inherited, I&#39;m still puzzled by the fact that a user with 32k reputation would say its not. I wrote a little example that should clarify everyone&#39;s mind:

    #include &lt;cstdio&gt;

    /******************************/

    // Base class
    struct A
    {
        A() { printf( &quot;\tInstance counter = %d (ctor)\n&quot;, ++instance_counter ); }
        ~A() { printf( &quot;\tInstance counter = %d (dtor)\n&quot;, --instance_counter ); }

        static int instance_counter;
    };

    // Inherited class with default ctor/dtor
    class B : public A {};

    // Inherited class with defined ctor/dtor
    struct C : public A
    {
        C() { printf(&quot;\tC says hi!\n&quot;); }
        ~C() { printf(&quot;\tC says bye!\n&quot;); }
    };

    /******************************/

    // Initialize counter
    int A::instance_counter = 0;

    /******************************/

    // A few tests
    int main()
    {
        printf(&quot;Create A\n&quot;); A a;
        printf(&quot;Delete A\n&quot;); a.~A();

        printf(&quot;Create B\n&quot;); B b;
        printf(&quot;Delete B\n&quot;); b.~B();

        printf(&quot;Create new B stored as A*\n&quot;); A *a_ptr = new B();
        printf(&quot;Delete previous pointer\n&quot;); delete a_ptr;

        printf(&quot;Create C\n&quot;); C c;
        printf(&quot;Delete C\n&quot;); c.~C();

    }

and here is the output (compiled with g++ 4.4.3):

    Create A
        Instance counter = 1 (ctor)
    Delete A
        Instance counter = 0 (dtor)
    Create B
        Instance counter = 1 (ctor)
    Delete B
        Instance counter = 0 (dtor)
    Create new B stored as A*
        Instance counter = 1 (ctor)
    Delete previous pointer
        Instance counter = 0 (dtor)
    Create C
        Instance counter = 1 (ctor)
        C says hi!
    Delete C
        C says bye!
        Instance counter = 0 (dtor)  // We exit main() now
        C says bye! 
        Instance counter = -1 (dtor)
        Instance counter = -2 (dtor)
        Instance counter = -3 (dtor)

**Q2:** Can anybody who thinks it&#39;s not inherited please explain that?

**Q3:** So what happens when you call the constructor of a subclass with inputs? Is the &quot;empty constructor&quot; of the superclass called as well?

C++ Constructor/Destructor inheritance

I was thinking: they say if you&#39;re calling destructor manually - you&#39;re doing something wrong. But is it always the case? Are there any counter-examples? Situations where it is neccessary to call it manually or where it is hard/impossible/impractical to avoid it?

Is calling destructor manually always a sign of bad design?

I&#39;m having trouble with Qt signals.

I don&#39;t understand how `DirectConnection` and `QueuedConnection` works?

I&#39;d be thankful if someone will explain when to use which of these (sample code would be appreciated).


Content Type	Original Author	Original Content on Stackoverflow
Question	daisy	View Question on Stackoverflow
Solution 1 - Qt	Mat	View Answer on Stackoverflow

Are signals in Qt automatically disconnected when one of the class is deleted

Qt Problem Overview

Qt Solutions

Solution 1 - Qt

How to open a PDF via Intent from SD card

Command to get svn diff of current and previous revision number

Attributions