Dietmar Kuehl (kuehl@uzwil.informatik.uni-konstanz.de) wrote:

> OTOH, as Tim Hollebeek observed in a thread in comp.lang.c++.moderated
> (Placement new and arrays), the usefulness of placement array new is
> limited anyway: There is no portable way to figure out how much
> "allocation overhead" there will be and thus it is impossible to
> predict how much memory has to be set aside for a placement array new.

But there is a way to way to figure out how much is "allocation overhead"!
Here an example:

void* operator new[](size_t size, size_t& retSize) {
   retSize = size;
   return NULL;
}

So you can call write something like this:

class T { ... };
...
size_t size;
new(size) T[100];
T* p = new(alloca(size)) T[100]; // allocate memory from stack
...
for (int i = 99; i >= 0; i--) { p[i].~T(); }
  // instead of placement delete ...

--
With best regards, Igor Boukanov
igor.boukanov@fi.uib.no  http://www.fi.uib.no/~boukanov
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