delete vs delete[] [duplicate]

Question

Possible Duplicate:
What is the difference between delete and delete[]?

When I was taught C++, this was a long time ago. I was told to never use delete but delete[] as performing delete[] on a single object will be equivalent to delete. Knowing not to trust teachers too much I wonder, Is this true?

Is there ever a reason to call delete instead of delete[]?

I've scanned the possibly related questions in SO, but haven't found any clear answer.

Jerrybuilt

/me throws up a little. Did they recommend you always call new[1] as well? – Disadvantage

Don't trust them when they tell "never". All strong statements are wrong. – Pahlavi

Actually there're small range of cases where you need to use delete[] in C++. It is better to use std::vector or boost::array. – Pahlavi

@Kirill "All strong statements are wrong." this statement is paradoxical. – Handset

If use valgrind --leak-check=full ./(binary name) you will get warning "Mismatched free() / delete / delete []". It is better to compile your program with valgrind to check for memory related queries. – Medea

lol, "All strong statements are wrong", is a strong statement. – Venereal

I'm pretty sure that was his joke. – Sizar

Answer 1

From the standard (5.3.5/2) :

In the first alternative (delete object), the value of the operand of delete shall be a pointer to a non-array object or a pointer to a sub-object (1.8) representing a base class of such an object (clause 10). If not, the behavior is undefined.

In the second alternative (delete array), the value of the operand of delete shall be the pointer value which resulted from a previous array new-expression. If not, the behavior is undefined.

So no : they are in no way equivalent !

Ordeal

Answer 2

delete [] is "vector delete" and corresponds to vector new, i.e. new[].

You must use the matching pair of allocators. E.g. malloc/free, new/delete, new[]/delete[], else you get undefined behavior.

Rosenwald

The word "vector" in the response should be changed to "native C-style array" ? Otherwise it is just a bit confusing perhaps. – Epizootic

No, vector and scalar new/delete are well understood terms. – Rosenwald

Answer 3

No! you call delete[] when you allocate with new[], otherwise you call delete.

What teacher told you leads to undefined behaviour and, if you are lucky, an application crash.

Huihuie

Answer 4

delete is used to delete a single object, while delete[] is used to delete an array of objects. Check this link for more info.

Subway