Date: Thu, 10 Apr 1997 15:48:44 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: current@freebsd.org Subject: WHY? ...non-use of TAILQ macros... Message-ID: <199704102248.PAA10021@phaeton.artisoft.com>
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On the theory that the TAILQ_xxx macros were being avoided and the
queue elemments themselves directly refernce for No Good Reason(tm),
I just compiled the following:
-----------------------------------------------------------------------------
#include <stdio.h>
struct node {
int element;
int filler;
int what;
};
struct node bob = {
1,
2,
3
};
main()
{
int j;
j = bob.what; /* 111*/
printf( "j = %d\n", j);
j = (&bob)->what; /* 222*/
printf( "j = %d\n", j);
}
-----------------------------------------------------------------------------
And got:
-----------------------------------------------------------------------------
.file "try.c"
gcc2_compiled.:
___gnu_compiled_c:
.globl _bob
.data
.align 2
.type _bob,@object
.size _bob,12
_bob:
.long 1
.long 2
.long 3
.text
LC0:
.ascii "j = %d\12\0"
.align 2
.globl _main
.type _main,@function
_main:
pushl %ebp
movl %esp,%ebp
subl $4,%esp
call ___main
movl _bob+8,%eax ; 1
movl %eax,-4(%ebp) ; 1
movl -4(%ebp),%eax ; 1
pushl %eax ; 1
pushl $LC0 ; 1
call _printf ; 1
addl $8,%esp ; 1
movl _bob+8,%eax ; 2
movl %eax,-4(%ebp) ; 2
movl -4(%ebp),%eax ; 2
pushl %eax ; 2
pushl $LC0 ; 2
call _printf ; 2
addl $8,%esp ; 2
L5:
leave
ret
Lfe1:
.size _main,Lfe1-_main
-----------------------------------------------------------------------------
... in other words, the references:
(x).y
and
(x)->y
Don't somehow generate different code.
I'm wondering why the following aren't written using the macros (macro
versions are shown one line below):
-----------------------------------------------------------------------------
kern_lockf.c: while (ltmp = overlap->lf_blkhd.tqh_first) {
while (ltmp = TAILQ_FIRST(&overlap->lf_blkhd)) {
kern_lockf.c: while (wakelock = listhead->lf_blkhd.tqh_first) {
while (wakelock = TAILQ_FIRST(&listhead->lf_blkhd)) {
kern_lockf.c: if (lock->lf_blkhd.tqh_first)
if (!TAILQ_EMPTY(&lock->lf_blkhd))
kern_lockf.c: printf(" block 0x%x\n", lock->lf_blkhd.tqh_first);
printf(" block 0x%x\n", TAILQ_FIRST(&lock->lf_blkhd));
kern_lockf.c: for (blk = lf->lf_blkhd.tqh_first; blk;
for (blk = TAILQ_FIRST(&lf->lf_blkhd); blk;
kern_lockf.c: if (blk->lf_blkhd.tqh_first)
if (!TAILQ_EMPTY(&blk->lf_blkhd))
kern_synch.c: for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
for (p = TAILQ_FIRST(qp); p != NULL; p = TAILQ_NEXT(p, p_procq)) {
kern_synch.c: for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
for (p = TAILQ_FIRST(qp); p != NULL; p = TAILQ_NEXT(p, p_procq)) {
uipc_socket.c: if (so->so_comp.tqh_first == NULL)
if (TAILQ_EMPTY(&so->so_comp))
uipc_socket.c: for (sp = so->so_incomp.tqh_first; sp != NULL; sp = sonext) {
for (sp = TAILQ_FIRST(&so->so_incomp); sp != NULL; sp = sonext) {
uipc_socket.c: for (sp = so->so_comp.tqh_first; sp != NULL; sp = sonext) {
for (sp = TAILQ_FIRST(&so->so_comp); sp != NULL; sp = sonext) {
uipc_syscalls.c: if ((head->so_state & SS_NBIO) && head->so_comp.tqh_first == NULL) {
if ((head->so_state & SS_NBIO) && TAILQ_EMPTY(&head->so_comp)) {
uipc_syscalls.c: while (head->so_comp.tqh_first == NULL && head->so_error == 0) {
while (TAILQ_EMPTY(&head->so_comp) && head->so_error == 0) {
uipc_syscalls.c: so = head->so_comp.tqh_first;
so = TAILQ_FIRST(&head->so_comp);
vfs_cache.c: ((ncp = nclruhead.tqh_first) == NULL ||
((ncp = TAILQ_FIRST(&nclruhead)) == NULL ||
vfs_cache.c: } else if (ncp = nclruhead.tqh_first) {
} else if (ncp = TAILQ_FIRST(&nclruhead)) {
vfs_subr.c: vnode_free_list.tqh_first == NULL) {
TAILQ_EMPTY(&vnode_free_list)) {
vfs_subr.c: for (vp = vnode_free_list.tqh_first;
for (vp = TAILQ_FIRST(&vnode_free_list);
vfs_subr.c: vnode_free_list.tqh_first != vp) {
TAILQ_FIRST(&vnode_free_list) != vp) {
-----------------------------------------------------------------------------
It seems to me that queue structure contents should only ever be referenced
or mainipulated in the context of queue structure reference macros...
One would also think that there would be:
#define TAILQ_ENUM(elm,head,field) \
for( elm = (head)->tqh_first; elm != NULL; elm = (elm)->field.tqe_next)
In queue.h to change:
kern_synch.c: for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) {
Into:
TAILQ_ENUM(p, qp, p_procq) {
Regards,
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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