I see in C++ there are multiple ways to allocate and free data and I understand that when you call malloc
you should call free
and when you use the new
operator you should pair with delete
and it is a mistake to mix the two (e.g. Calling free()
on something that was created with the new
operator), but I'm not clear on when I should use malloc
/ free
and when I should use new
/ delete
in my real world programs.
If you're a C++ expert, please let me know any rules of thumb or conventions you follow in this regard.
Unless you are forced to use C, you should never use malloc
. Always use new
.
If you need a big chunk of data just do something like:
char *pBuffer = new char[1024];
Be careful though this is not correct:
//This is incorrect - may delete only one element, may corrupt the heap, or worse...
delete pBuffer;
Instead you should do this when deleting an array of data:
//This deletes all items in the array
delete[] pBuffer;
The new
keyword is the C++ way of doing it, and it will ensure that your type will have its constructor called. The new
keyword is also more type-safe whereas malloc
is not type-safe at all.
The only way I could think that would be beneficial to use malloc
would be if you needed to change the size of your buffer of data. The new
keyword does not have an analogous way like realloc
. The realloc
function might be able to extend the size of a chunk of memory for you more efficiently.
It is worth mentioning that you cannot mix new
/free
and malloc
/delete
.
Note: Some answers in this question are invalid.
int* p_scalar = new int(5); // Does not create 5 elements, but initializes to 5
int* p_array = new int[5]; // Creates 5 elements