"void **" : Is it valid and what does it mean?

[Richard A. O'Keefe]

Yes, void ** is valid, and it means pointer-to-generic pointer.
Note that void ** itself may be represented some other way entirely;
void ** is not itself a generic pointer.

In article <AJ3U.91May27213633 at jade.cs.virginia.edu>, aj3u at jade.cs.virginia.edu (Asim Jalis) writes:
> func(void **p)
> { ... }
> 
> main()
> { int *i; float *f; char *c;
> 
>   func(&i); func(&f); func(&c);
> }
> 
> However, the compiler gives me warnings about incompatible type for
> all the function calls.

The compiler is RIGHT.  You promised it (oh, you deceiver) that
you would give func() pointers to generic (void*) pointers
(call the representation of generic pointers REPRESENTATION 0)
But you lied (oh, you scoundrel, you).  You gave it
    -- a pointer to (a pointer to int  -- REPRESENTATION 1)
    -- a pointer to (a pointer to float -- REPRESENTATION 2)
    -- a pointer to (a pointer to char -- REPRESENTATION 0)
char* and void* use the same representation.
But void*, int*, and float* need not even be the same _size_, let
alone use the same physical representation.

> The code itself works fine,

no, there is a bug in there, waiting, like a blood-sucking insect
poised on a bush waiting for a deer to pass by, for an opportunity to bite.

> Basically what I want is a type that would coerce to a pointer to a
> pointer to a type, for any type.  Sort of one level beyond simple
> "void *".

Why do you want to do _that_?  If you _could_ do it, you would be
throwing away information that the receiver would need in order to
be able to _use_ the thing?  What's the context?

-- 
Should you ever intend to dull the wits of a young man and to
incapacitate his brains for any kind of thought whatever, then
you cannot do better than give him Hegel to read.  -- Schopenhauer.