GCC aliasing extension for C

[Florian Weimer]

I know that GCC implements a C extension (which is more or less required 
by POSIX) which allows you to define a buffer

  char buf[1024];
and then allocate objects from that (assuming that the buffer is 
sufficiently large and the pointers to subobjects are suitably aligned). 
 In short, it is possible to change the dynamic type of an object even 
if it was defined with a type.

The object is first written under the new type, and only accessed under 
the new type.  It is also possible that the buffer is reused and 
different objects with different types at the same offsets are carved 
out from it.

Is this a property of the char type, or would other types work as well, 
for example, double or long double?

Thanks,
Florian