Interview : C++ Interview Questions (Page - 4)
What is name mangling in C++?
The process of encoding the parameter types with the function/method name into a
unique name is called name mangling. The inverse process is called demangling.
For example Foo::bar(int, long) const is mangled as `bar__C3Fooil'.
For a constructor, the method name is left out. That is Foo::Foo(int, long)
const is mangled as `__C3Fooil'.
What is the difference between a pointer and a reference?
A reference must always refer to some object and, therefore, must always be
initialized; pointers do not have such restrictions. A pointer can be reassigned
to point to different objects while a reference always refers to an object with
which it was initialized.
How are prefix and postfix versions of operator++() differentiated? The postfix
version of operator++() has a dummy parameter of type int. The prefix version
does not have dummy parameter.
What is the difference between const char *myPointer and char *const myPointer?
Const char *myPointer is a non constant pointer to constant data; while char
*const myPointer is a constant pointer to non constant data.
How can I handle a constructor that fails?
throw an exception. Constructors don't have a return type, so it's not
possible to use return codes. The best way to signal constructor failure is
therefore to throw an exception.
How can I handle a destructor that fails?
Write a message to
a log-file. But do not throw an exception.
The
C++ rule is that you must never throw an exception from a destructor that is
being called during the "stack unwinding" process of another
exception. For example, if someone says throw Foo(), the stack will be unwound
so all the stack frames between the throw Foo() and the } catch (Foo e) { will
get popped. This is called stack unwinding. During stack unwinding, all
the local objects in all those stack frames are destructed. If one of those
destructors throws an exception (say it throws a Bar object), the C++ runtime
system is in a no-win situation: should it ignore the Bar and end up in the }
catch (Foo e) { where it was originally headed? Should it ignore the Foo and
look for a } catch (Bar e) { handler? There is no good answer -- either choice
loses information. So the C++ language guarantees that it will call terminate()
at this point, and terminate() kills the process. Bang you're dead.
What
is Virtual Destructor?
Using virtual
destructors, you can destroy objects without knowing their type - the correct
destructor for the object is invoked using the virtual function mechanism. Note
that destructors can also be declared as pure virtual functions for abstract
classes. if someone will derive from your class, and if someone will say
"new Derived", where "Derived" is derived from your class,
and if someone will say delete p, where the actual object's type is
"Derived" but the pointer p's type is your class. Can you think of a
situation where your program would crash without reaching the breakpoint which
you set at the beginning of main()? C++ allows for dynamic initialization of
global variables before main() is invoked. It is possible that initialization of
global will invoke some function. If this function crashes the crash will occur
before main() is entered. Name two cases where you MUST use initialization list
as opposed to assignment in constructors. Both non-static const data members and
reference data members cannot be assigned values; instead, you should use
initialization list to initialize them.
Can
you overload a function based only on whether a parameter is a value or a
reference?
No. Passing by
value and by reference looks identical to the caller.
What
are the differences between a C++ struct and C++ class?
The default member
and base class access specifiers are different.
The C++ struct has all the features of the class. The only differences are that
a struct defaults to public member access and public base class inheritance, and
a class defaults to the private access specifier and private base class
inheritance.
What
does extern "C" int func(int *, Foo) accomplish?
It will turn off
"name mangling" for func so that one can link to code compiled by a C
compiler.
How
do you access the static member of a class?
<ClassName>::<StaticMemberName>
What is multiple inheritance(virtual inheritance)? What are its advantages
and disadvantages?
Multiple Inheritance is the process whereby a child can be derived from more
than one parent class. The advantage of multiple inheritance is that it allows a
class to inherit the functionality of more than one base class thus allowing for
modeling of complex relationships. The disadvantage of multiple inheritance is
that it can lead to a lot of confusion(ambiguity) when two base classes
implement a method with the same name.
