What is the difference between new and malloc() in C++?

Table of Contents

• Introduction
• Differences Between new and malloc()
  • Memory Allocation and Initialization
  • Type Safety
  • Exception Handling
  • Deallocation of Memory
• Practical Examples
  • Example 1: Allocating and Initializing an Object
  • Example 2: Allocating an Array
• Conclusion

Introduction

In C++, dynamic memory allocation is a critical aspect of programming, allowing the creation of objects and arrays during runtime. Two common methods for dynamic memory allocation are the new operator and the malloc() function. While both are used to allocate memory, they have distinct differences in functionality, usage, and behavior. Understanding these differences is essential for effective memory management in C++.

Differences Between new and malloc()

Memory Allocation and Initialization

• new Operator: The new operator not only allocates memory but also initializes the object by calling its constructor. This makes new more suitable for C++ as it supports object-oriented programming.

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• malloc() Function: The malloc() function, inherited from C, only allocates a block of memory of a specified size. It does not perform any initialization, leaving the memory block with garbage values if not explicitly initialized.

  Example:

Type Safety

• new Operator: The new operator is type-safe. It automatically returns a pointer of the appropriate type, ensuring that there is no need for type casting.

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• malloc() Function: The malloc() function returns a void* pointer, requiring an explicit cast to the desired data type, which can lead to errors if the wrong type is used.

  Example:

Exception Handling

• new Operator: The new operator throws a std::bad_alloc exception if memory allocation fails, allowing for proper exception handling in C++ programs.

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• malloc() Function: The malloc() function returns NULL if memory allocation fails, requiring the programmer to manually check for NULL pointers and handle the error.

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Deallocation of Memory

• new Operator: Memory allocated with new must be deallocated using the delete operator for single objects or delete[] for arrays. This ensures that destructors are called for object cleanup.

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• malloc() Function: Memory allocated with malloc() must be deallocated using the free() function. There is no automatic calling of destructors, making malloc() less suited for object-oriented programming.

  Example:

Practical Examples

Example 1: Allocating and Initializing an Object

Using new, the object is automatically initialized via its constructor, while with malloc(), you need to manually initialize the object's members.

Using new:

Using malloc():

Example 2: Allocating an Array

The new[] operator is used to allocate arrays, ensuring all elements are initialized, while malloc() allocates a block of memory without initialization.

Using new[]:

Using malloc():

Conclusion

The new operator and malloc() function serve similar purposes in C++, but they differ significantly in terms of memory allocation, initialization, type safety, and error handling. The new operator is more aligned with C++'s object-oriented principles, automatically handling initialization and offering type safety and exception handling. In contrast, malloc() is a C-style function that requires manual initialization and type casting. Understanding these differences is crucial for writing efficient and robust C++ programs.