destructors of array placement new

Question

I haven't been able to find an answer for this :

T * blockPtr = static_cast<T*>(malloc(nb*sizeof(T)));
new (blockPtr) T[nb];
// use my blockPtr array
// call destructors (?)
free(blockPtr);

In that case, what is the correct way to call destructors ? Should I manually loop on every item and call every destructor or is there a specific syntax to do this in one call ? I know that when calling delete[] on a class T, some compilers like MSVC usually have behind the scene a specific "vector destructor" to do this.

Answer 1

Should I manually loop on every item and call every destructor

Yes.

is there a specific syntax to do this in one call ?

No.

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I hope you really need to do this!

Answer 2

When using placement-new, you have to call the destructors yourself:

void * blockPtr = malloc(nb*sizeof(T));
T * block = new (blockPtr) T[nb];

// use block array ...

// call destructors
for (int i = 0; i < nb; ++i)
    block[i].~T();

free(blockPtr);