🚀 go-pugleaf

davis@space.mit.edu writes:
[on a DPS-6000]
>So, does this fail:
>
>   double *d;
>   char *p;
>   unsigned int size;
>   
>   size = sizeof (double);
>   d = malloc (size);
>   p = malloc (size);
>   
>What is the difference between d and p?  Is malloc smart enough to know
>which representation to return?

malloc returns a void *. The assignments to d and p convert the void * to
double * and char *, respectively. No change is needed for the char *, but
the return value from malloc is reduced from 32 bits to 16 bits to convert
to a double *. Since malloc guarantees alignment (actually, only *after*
casting, but only a very malicious malloc would do that to you), this can
safely be done.

The DPS-6000 has 16-bit words. A word address fits into one 16-bit word. An
extra bit is needed, in another word, to distinguish the two bytes in a word.
I think this "byte" pointer is a an artefact of the C implementation, to save
space: the hardware itself thinks bytes are words are 16 bits.
-- 
David Tanguay       dat@Thinkage.on.ca       http://www.thinkage.on.ca/~dat/
Thinkage, Ltd.           Kitchener, Ontario, Canada          [43.24N 80.29W]