Databases
StackOverflow2013
Postsdbo
POVirtual tables and memory layout in multiple virtual inheritance
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POVirtual tables and memory layout in multiple virtual inheritance
    primarykey
    data
    text
    <p>Consider following hierarchy:</p> <pre><code>struct A { int a; A() { f(0); } A(int i) { f(i); } virtual void f(int i) { cout &lt;&lt; i; } }; struct B1 : virtual A { int b1; B1(int i) : A(i) { f(i); } virtual void f(int i) { cout &lt;&lt; i+10; } }; struct B2 : virtual A { int b2; B2(int i) : A(i) { f(i); } virtual void f(int i) { cout &lt;&lt; i+20; } }; struct C : B1, virtual B2 { int c; C() : B1(6),B2(3),A(1){} virtual void f(int i) { cout &lt;&lt; i+30; } }; </code></pre> <ol> <li><p>What's the <strong>exact</strong> memory layout of <code>C</code> instance? How many vptrs it contains, where exactly each of them is placed? Which of virtual tables are shared with virtual table of C? What exactly each virtual table contains? </p> <p>Here how I understand the layout: </p> <pre><code>---------------------------------------------------------------- |vptr1 | AptrOfB1 | b1 | B2ptr | c | vptr2 | AptrOfB2 | b2 | a | ---------------------------------------------------------------- </code></pre> <p>where <code>AptrOfBx</code> is the pointer to <code>A</code> instance that <code>Bx</code> contains (since the inheritance is virtual).<br> Is that correct? Which functions <code>vptr1</code> points to? Which functions <code>vptr2</code> points to?</p></li> <li><p>Given the following code</p> <pre><code>C* c = new C(); dynamic_cast&lt;B1*&gt;(c)-&gt;f(3); static_cast&lt;B2*&gt;(c)-&gt;f(3); reinterpret_cast&lt;B2*&gt;(c)-&gt;f(3); </code></pre> <p>Why all the calls to <code>f</code> print <code>33</code>?</p></li> </ol>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USmeltedspark
    1. USmeltedspark
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POVirtual tables and memory layout in multiple virtual inheritance
      1. This table or related slice is empty.
      1. VTDownMod
    2. VO
      singulars
      1. POVirtual tables and memory layout in multiple virtual inheritance
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POVirtual tables and memory layout in multiple virtual inheritance
      1. This table or related slice is empty.
      1. VTUpMod
    1. COIs this homework, or curiosity?
      singulars
      1. POVirtual tables and memory layout in multiple virtual inheritance
      1. UStemplatetypedef
    2. COActually this is exam. But I'm sure, if I finally understand how the things works in this example, I can understand anything which related to multiple inheritance and virtual inheritance.
      singulars
      1. POVirtual tables and memory layout in multiple virtual inheritance
      1. USmeltedspark
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload