Date: Thu, 08 Jan 2004 21:14:10 +0100 From: des@des.no (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=) To: alpha@freebsd.org Subject: structure padding Message-ID: <xzpoete42r1.fsf@dwp.des.no>
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In -STABLE, struct kinfo_proc is currently defined as follows:
struct kinfo_proc {
struct proc kp_proc;
struct eproc {
/* ... */
char e_login[roundup(MAXLOGNAME, sizeof(long))];
long e_spare[2];
} kp_eproc;
};
I want to add an e_sid field to hold the process's session ID:
struct kinfo_proc {
struct proc kp_proc;
struct eproc {
/* ... */
char e_login[roundup(MAXLOGNAME, sizeof(long))];
pid_t e_sid;
long e_spare[1];
} kp_eproc;
};
However, a pid_t is an int, and sizeof int != sizeof long on Alpha.
I'm not sure what will happen: will alignment rules cause gcc to add
four bytes of padding before e_spare, conserving the size of struct
kinfo_proc, or will struct kinfo_proc shrink by four bytes?
DES
--
Dag-Erling Smørgrav - des@des.no
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