Defining the fields of a structure at run-time

[nambissan.nisha]

I am facing this problem....
I have to define a structure at runtime as the user specifies...

The user will tell the number of fields,the actual fields...(maybe
basic or array types or multiple arrays,etc)

I do not understand how to define the structure at run time.i.e.what
fields it will contain.
Creating the field variables at run time is fine...but defining the
structure so as to contain these fields is where the problem lies...

I thought of unions within the structure representing each possible
field variable...
but again only one of these unions can exist at time...array of unions
again similar problem.

Any possible solution occuring to any one...please do let me know as
early as possible.
Thanks a lot...

Nisha.

[Flash Gordon]

stathis gotsis wrote:

"Flash Gordon" <sp**@flash-gordon.me.uk> wrote in message
news:mq******** ****@news.flash-gordon.me.uk...
<snip>
Impressive, i had no idea about this!

That is what we are here for, increasing peoples knowledge :-)

So what you have to do is the reverse of when you put the data in. I.e.:
memcpy(i, a+member_offset[0], member_size[0]);
printf("Integer is: %d\n", i);
Ideally you should add at least basic error trapping, i.e.
if (member_size[0] != sizeof i)
fputs("ERROR: Size miss-match!\n");
else {
memcpy(i, a+member_offset[0], member_size[0]);
printf("Integer is: %d\n", i);
}

All is perfectly clear now, but why the error checking since i should have
explicitly set member_size[0] to sizeof(i) earlier in the program anyway?

It's called defensive programming. Although you believe that the size is
always explicitly set, there is always the possibility of error. Such as
your assumption that an int is 2 bytes! It also helps to catch something
having gone wrong corrupting the contents of member_size.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.