You are tasked with enhancing the performance of a critical path in an application. You identify a function that is called very frequently as a potential optimization target. Which specific aspect of the return statement could you focus on to possibly improve performance, especially considering modern C++ standards?
- Returning by value.
- Returning by pointer.
- Using return in a loop to optimize iterations.
- Returning by reference or moving.
In modern C++, when considering performance-critical paths, it's beneficial to understand the difference between returning by value and returning by reference or using move semantics. Especially with the advent of Rvalue references in C++11, returning by reference or moving can avoid unnecessary copies and lead to significant performance improvements. Returning by pointer is less idiomatic and might not convey ownership semantics clearly.
When passing parameters by reference, which symbol is used to denote reference in C++?
- #
- @
- &
- %
In C++, the ampersand (&) is used to denote that a parameter is being passed by reference. This allows the function to directly access and modify the actual argument's memory location.
What is the purpose of the this pointer in C++?
- To return the current object's address.
- To point to global variables.
- To create a new object.
- To delete the current object.
In C++, the this pointer is used within a class's member function to refer to the invoking object of that function. It's an implicit parameter to all member functions and contains the memory address of the current object, allowing for operations on the calling object itself.
You are tasked with optimizing a piece of code containing nested loops...
- Move calculations outside of the loops.
- Replace inner loop with a lookup table.
- Inline the inner loop calculations.
- Prefetch data before processing in the inner loop.
A lookup table can be used to store pre-computed results of complex calculations. By replacing the inner loop's calculations with lookups from this table, one can often achieve significant speedups, especially if the same calculations are being performed repeatedly.
What happens if an exception occurs in a destructor in C++?
- The program will retry the destructor
- A default destructor is called
- The program terminates
- The exception is ignored
If an exception is thrown from a destructor, and it's not caught within the destructor, the C++ runtime system will terminate the program. Destructors are often invoked during stack unwinding when an exception is thrown, so allowing exceptions to propagate out can lead to unpredictable behavior.
You are developing a financial application with various account types. How would you design the classes to achieve this and allow future modifications?
- Singleton Pattern
- Composition
- Prototype Pattern
- Inheritance and Polymorphism
Using inheritance, a base class 'Account' can be created with methods like 'withdraw', 'deposit', and 'calculateInterest'. Derived classes like 'SavingsAccount', 'CurrentAccount', etc., can then override these methods to provide specific implementations. Polymorphism ensures these methods are called appropriately.
Imagine you are developing a real-time gaming application where performance is critical. Which type of function (regular/inline) might you prefer to use for small, frequently-used utility calculations, and why?
- Regular functions due to easier debugging.
- Inline functions for performance optimization.
- Regular functions for better code organization.
- Inline functions due to easier maintenance.
Inline functions are usually preferred for small, frequently-used utility calculations in performance-critical applications like games because the compiler replaces the inline function call with the actual code, eliminating the overhead of a function call.
You are building a configuration parser for a C++ application...
- Use std::ifstream and check its state
- Read entire file and validate before parsing
- Use regular expressions to parse
- Use std::fscanf
When using std::ifstream, it's possible to check the state of the stream (e.g., fail(), bad(), eof()) after operations. This allows for robust error handling by identifying issues like file corruption. Ensuring stream integrity before operations can prevent runtime issues.
In terms of object-oriented design principles, what is typically the most significant critique against the use of friend functions?
- They break encapsulation.
- They increase execution time.
- They aren't necessary in OOP.
- They cause memory leaks.
Friend functions have the ability to access private and protected members of a class, which can be seen as a violation of the principle of encapsulation in object-oriented programming. While they offer flexibility, they can break the boundaries set by encapsulation.
Which of the following C++ standards introduced smart pointers?
- C++03
- C++11
- C++14
- C++98
Smart pointers, like std::shared_ptr, std::unique_ptr, and std::weak_ptr, were introduced in C++11. They are part of the C++ Standard Library and are designed to manage the lifecycle of dynamically allocated objects, preventing memory leaks.
Which of the following data types can store a non-integer number?
- char
- float
- int
- short
In C++, the float data type is used to store single-precision floating-point numbers, which can represent non-integer values (like 3.14). It provides a way to store decimal numbers with a floating decimal point.
What is the main purpose of using protected access specifier in base class?
- To restrict all external access
- To allow all classes to access
- To enable inheritance only
- To share methods with friends
The protected access specifier in C++ is mainly used to ensure that members are inaccessible from outside the class (just like private members). However, the difference is that protected members can be accessed by derived classes. This allows for more secure inheritance, giving derived classes access without exposing to the external world.