Re: style: structures

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> [...], using the C standard guaranteed property that the address of
> the first member is the address of the structure, allowing to cast
> pointers in order to operate whether on the base structure or on the
> derived structure?

Which standard promises this, and what exactly does it promise?  I've
been looking through C99 and the closest I've found so far is 6.5.2.3
#5, which is not quite the same:

       6.5.2.3  Structure and union members
...
       [#5]  One special guarantee is made in order to simplify the
       use of unions: if a union contains several  structures  that
       share  a  common  initial  sequence  (see below), and if the
       union object currently contains one of these structures,  it
       is  permitted  to  inspect the common initial part of any of
       them anywhere that a declaration of the  completed  type  of
       the union is visible.  Two structures share a common initial
       sequence if  corresponding  members  have  compatible  types
       (and, for bit-fields, the same widths) for a sequence of one
       or more initial members.

Also, "address" as a technical term in C99 is very fuzzy, to the point
where I doubt that the statement that "the address of the first member
is the address of the structure" has a defined meaning.  (It certainly
will for many implementations, but that is not the same thing.)  Have
more recent standards turned it into something more specific?

I really need to chase down a copy of something more recent and turn it
into a useful form...I've got pointers, but need to follow them.

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