CentOS - Dec 2013 - about C program of CPP macro problems

Hello, all:

I have a program problem, ( may it not have close releationship with
Debian), it described like this:

I want to using #define / #undef, and want to put them in a single macro,
some thing like:

#define DECALRE_TYPE(type) \
{ #undef __curr_type;  #define _curr_type type; }

as we know, this can not passed with CPP, but I need this logical here.

Generally, the problem comes from

#define ser_field(type, var) \
    ser_new_field(tra, #type, #var, offsetof(struct_type, var))

I do not want another additional parameter in this macro like

#define ser_field(type,var,struct_type), and I want a sentence declare
"current struct type"
and all later work of ser_field will defaultly use this type.

I am not sure whether I can express it clearly, any ideas will be greately
appreciated!


Thanks and B.R.


2013/12/10 John Doe <jdmls at yahoo.com>
> From: Lars Hecking <lhecking at users.sourceforge.net>
>
> > One thing I have noticed on CentOS6 is that rsync via xinetd never
> > works after a reboot. It always takes an additional, post-reboot
> > service xinetd restart to get it going. That has been the same for
> > all revisions up to and including 6.5, and I've seen it on more
than
> > just machine.
> >
> > While I don't see such a message on other problem machines, the
latest
> > reboot gave me a clue:
> >
> > Dec  9 23:28:36 host xinetd[21131]: bind failed (Address already in
use
> (errno > > 98)). service = rsync
> > Dec  9 23:28:36 host xinetd[21131]: Service rsync failed to start and
is
> > deactivated.
> >
> > Is there any way to debug this? I suspect it needs to be debugged
> > during reboot since the service starts up fine later.
>
> "Address already in use" => check what is listening on port
873?
> In the rsync xinetd conf it says IPv6 here...
>
> JD
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> CentOS at centos.org
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>

On Tue, 10 Dec 2013, Nicol TAO wrote:
> I want to using #define / #undef, and want to put them in a single macro,
> some thing like:
>
> #define DECALRE_TYPE(type) \
> { #undef __curr_type;  #define _curr_type type; }
>
> as we know, this can not passed with CPP, but I need this logical here.
I think that you are out of luck.
The preprocessor will not macro-expand one line into more than one line.
Also, #s generated from macro-expansion do not count as preprocessor flags.

To get two lines from one, you need #include.
#include "dcltype"
Have one such file per type.
> Generally, the problem comes from
>
> #define ser_field(type, var) \
>    ser_new_field(tra, #type, #var, offsetof(struct_type, var))
>
> I do not want another additional parameter in this macro like
>
> #define ser_field(type,var,struct_type), and I want a sentence declare
> "current struct type"
> and all later work of ser_field will defaultly use this type.
-- 
Michael   hennebry at web.cs.ndsu.NoDak.edu
"SCSI is NOT magic. There are *fundamental technical
reasons* why it is necessary to sacrifice a young
goat to your SCSI chain now and then."   --   John Woods