Proj user18: Proj user18 moved page Frequently Asked Interview Questions to Dynamic Memory Interview Questions

2016-12-18T10:17:49Z

Proj user18 moved page Frequently Asked Interview Questions to Dynamic Memory Interview Questions

Proj user18: Created page with "=== How does free() deallocate memory when no data related to size is passed as a parameter? === The memory allocation functions are implemented in such a way that certain me..."

2016-12-18T06:05:55Z

Created page with "=== How does free() deallocate memory when no data related to size is passed as a parameter? === The memory allocation functions are implemented in such a way that certain me..."

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=== How does free() deallocate memory when no data related to size is passed as a parameter? ===

The memory allocation functions are implemented in such a way that certain metadata for each allocated block is stored in-line or separately.

Considering in-line metadata, the header information contains the size which is checked by free to understand how much of memory needs to be deallocated.
<br>

=== What happens when free() is called on an already freed pointer? ===

The behaviour is undefined. It could result in a crash, memory corruption or a segmentation fault.<br>
A good practise is to make the pointer a NULL after freeing.
<syntaxhighlight lang="c">
free(pointer_to_be_freed);
pointer_to_be_freed = nullptr;
</syntaxhighlight>

=== How can primitive data types be allocated using new? ===
<syntaxhighlight lang="c">
int* i = new int(6);
</syntaxhighlight>

=== What are the differences between new and malloc? ===
{| class="wikitable"
|-
!
! scope="col"| malloc
! scope="col"| new
|-
! scope="row"| 1
| malloc is a function call
| new is an operator and can be overloaded
|-
! scope="row"| 2
| malloc is concerned with basic memory allocation
| new invokes the constructor
|-
! scope="row"| 3
| malloc returns a pointer to the memory block allocated which is of type void
| new returns a pointer of the exact datatype requested
|-
! scope="row"| 4
| malloc never throws exceptions. On failure, it returns a NULL pointer
| On failure, new throws std::bad_alloc exception
|-

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Dynamic Memory Interview Questions - Revision history

Proj user18: Proj user18 moved page Frequently Asked Interview Questions to Dynamic Memory Interview Questions

Proj user18: Created page with "=== How does free() deallocate memory when no data related to size is passed as a parameter? === The memory allocation functions are implemented in such a way that certain me..."