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Falk Tannhäuser
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 Posted: Tue Jul 08, 2003 1:36 am Post subject: Re: is C++ implementation allowed to store object in non-con |
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Mirek Fidler wrote:
| Quote: | There is some indication that C++ implementation is allowed to store
base class suboject of derived class in different chunk of memory. Is
that true ? What paragraphs of standard deal with this issue ? (closest
I have found is 3.9/5, but it does not seems to be definitive).
Think about multiple virtual inheritance!
If eventually it is (personally, I do not think so), how is e.g.
placement operator new expected to work ?
_____________________________________ |
#include <new>
struct A {};
struct B1 : public virtual A {};
struct B2 : public virtual A {};
struct C : public B1, public B2 {};
unsigned char mem_for_B1[sizeof(B1)];
unsigned char mem_for_C[sizeof(C)];
int main()
{
// hoping the unsigned char arrays are well aligned...
B1* b1 = new(mem_for_B1) B1;
C* c = new(mem_for_C) C;
return 0;
}
_____________________________________
I don't think there is something special concerning placement new
since you can use it only to construct ***complete objects***
which always occupy a continuous memory zone (even if the B1 or
B1 subobjects within a C object doesn't).
Falk
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