What is the difference between new/delete and malloc/free?

What is the difference between new/delete and malloc/free?

Related (duplicate?): In what cases do I use malloc vs new?

new / delete

• Allocate / release memory

• Memory allocated from 'Free Store'.

• Returns a fully typed pointer.

• new (standard version) never returns a NULL (will throw on failure).

• Are called with Type-ID (compiler calculates the size).

• Has a version explicitly to handle arrays.

• Reallocating (to get more space) not handled intuitively (because of copy constructor).

• Whether they call malloc / free is implementation defined.

• Can add a new memory allocator to deal with low memory (std::set_new_handler).

• operator new / operator delete can be overridden legally.

• Constructor / destructor used to initialize / destroy the object.

malloc / free

• Allocate / release memory

• Memory allocated from 'Heap'.

• Returns a void*.

• Returns NULL on failure.

• Must specify the size required in bytes.

• Allocating array requires manual calculation of space.

• Reallocating larger chunk of memory simple (no copy constructor to worry about).

• They will NOT call new / delete.

• No way to splice user code into the allocation sequence to help with low memory.

• malloc / free can NOT be overridden legally.

Table comparison of the features:

Feature
new / delete
malloc / free

Memory allocated from
'Free Store'
'Heap'

Returns
Fully typed pointer
void*

On failure
Throws (never returns NULL)
Returns NULL

Required size
Calculated by compiler
Must be specified in bytes

Handling arrays
Has an explicit version
Requires manual calculations

Reallocating
Not handled intuitively
Simple (no copy constructor)

Call of reverse
Implementation defined
No

Low memory cases
Can add a new memory allocator
Not handled by user code

Overridable
Yes
No

Use of constructor / destructor
Yes
No

Technically, memory allocated by new comes from the 'Free Store' while memory allocated by malloc comes from the 'Heap'. Whether these two areas are the same is an implementation detail, which is another reason that malloc and new cannot be mixed.

Stack Overflow Q#240212, score: 513