realloc without moving?

[chris <caj at cs dot york dot ac dot uk>]

Hello.

Is there a function in glibc like realloc, except in the case where it 
is not possible to extend the existing memory then instead of allocating 
a new block of memory and copying the old block into this area the 
function simply returns?

This would be very useful in C++ (and I imagine in some cases of C as 
well) as if an existing memory block cannot be extended, then in general 
we cannot simply bitcopy the classes into a new block, but must instead 
allocate a new block and use the class's copy constructors to move them 
into the new block. Similarily in C if a large complex data structure 
containing many pointers lived within an allocated block of memory then 
it probably cannot simply be copied bitwise but must be reassembled in 
the new memory segment.

Thank you,

Chris