-----Original Message-----
From: Nengming Zhang <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: 26 August 2000 07:16
Subject: C parse error, why?
>
>Sorry to ask this simple question!
>
>I don't do how ":" works In C program like the following example:
>
>int y:1; /* parse error*/
>struct _Test
>{
> int x :1; /* no parse error report*/
>}
The syntax x:1 is used to declare a bitfield -- that is, a way of allocating
less than a single byte for a variable. The compiler packs bitfield
variables together inside an integral number of bytes, which is why it
doesn't make sense to have a bitfield variable on its own, only as part of a
structure. For example,
struct _Test {
int x:4;
int y:4;
};
The whole structure only occupies 1 byte -- 4 bits are allocated to each
variable. If the structure only contained the x variable, it would still
occupy a byte -- the last 4 bits would be unused.
Hope this helps,
Glenn
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