Strict capacity of array

[FreeSlave]

Suppose some class contains slice (dynamic array) as data member. 
Constructor takes integer value that defines the size of data 
should be allocated. After object was constructed size of slice 
never changes by design.

Dynamic arrays are allocated with extra space that we can know 
from 'capacity' property. But how can I allocate exactly as much 
elements as I want? Because in case described above we don't need 
extra space.

I know it's possible to use malloc in constructor and free in 
destructor. But what if I want to expose inner slice by shallow 
copy (i.e. by copying pointer and size, but not underlined data) 
then use it just like usual dynamic array whose lifetime does not 
depend on lifetime of an object it belongs and is managed by GC?