Date: Wed, 6 Oct 2010 13:07:38 +0200 From: Erik Cederstrand <erik@cederstrand.dk> To: Tim Kientzle <tim@kientzle.com> Cc: FreeBSD Hackers <hackers@freebsd.org> Subject: Re: Timestamps in static libraries Message-ID: <A87D6BCE-59D2-435F-AAE6-8354F536689D@cederstrand.dk> In-Reply-To: <140AD250-ECD1-4BCF-806B-F5901B3BFD87@kientzle.com> References: <52C32EA5-A380-4237-A27C-9E2DF2D4E022@cederstrand.dk> <20101005135906.GA3430@owl.midgard.homeip.net> <C5C85BF7-3989-461E-A9C8-9D16AE779359@cederstrand.dk> <140AD250-ECD1-4BCF-806B-F5901B3BFD87@kientzle.com>
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Den 06/10/2010 kl. 08.00 skrev Tim Kientzle:
>>=20
>> % diff mod.strings orig.strings
>> 2c2
>> < / 1286312209 0 0 0 958 `
>> ---
>>> / 1269146263 0 0 0 958 `
>=20
> That's the timestamp on the pseudo-entry used to store the archive
> symbol table. (GNU/SysV ar files use a pseudo-entry named "/" to
> store the symbol table. Since '/' is added to end of names in this
> format, this is essentially an entry with an empty name.)
>=20
> The current ar code generates this entry and sets the timestamp
> around line 624 of usr.bin/ar/write.c.
>=20
> As far as I can tell, ar itself doesn't care about the timestamp here;
> it's possible that ranlib or ld do care. If they don't, we could set
> this timestamp to zero always.
Is something like the following acceptable? Without risking changes to =
buildworld/distribution just now, this would allow me to dump contents =
of an archive and re-insert them with '0' for mtime, uid and gid before =
checking checksums, without affecting normal ar behaviour.
erik% svn diff
Index: ar.1
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- ar.1 (revision 213478)
+++ ar.1 (working copy)
@@ -62,6 +62,7 @@
.Op Fl a Ar position-after
.Op Fl b Ar position-before
.Op Fl c
+.Op Fl D
.Op Fl i Ar position-before
.Op Fl j
.Op Fl s
@@ -179,6 +180,14 @@
.Ar archive .
The archive's symbol table, if present, is updated to reflect
the new contents of the archive.
+.It Fl D
+When used in combination with the=20
+.Fl r
+option, insterts 0's instead of the real mtime, uid and gid values
+from the members named by arguments
+.Ar files ... .
+This ensures that checksums on the resulting archives are reproducible
+when member contents are identical.
.It Fl f
Synonymous with option
.Fl T .
Index: ar.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- ar.c (revision 213478)
+++ ar.c (working copy)
@@ -154,7 +154,7 @@
}
}
=20
- while ((opt =3D getopt_long(argc, argv, =
"abCcdfijlMmopqrSsTtuVvxz",
+ while ((opt =3D getopt_long(argc, argv, =
"abCcdDfijlMmopqrSsTtuVvxz",
longopts, NULL)) !=3D -1) {
switch(opt) {
case 'a':
@@ -173,6 +173,9 @@
case 'd':
set_mode(bsdar, opt);
break;
+ case 'D':
+ bsdar->options |=3D AR_D;
+ break;
case 'f':
case 'T':
bsdar->options |=3D AR_TR;
@@ -357,8 +360,8 @@
(void)fprintf(stderr, "\tar -m [-Tabijsvz] position archive file =
...\n");
(void)fprintf(stderr, "\tar -p [-Tv] archive [file ...]\n");
(void)fprintf(stderr, "\tar -q [-Tcjsvz] archive file ...\n");
- (void)fprintf(stderr, "\tar -r [-Tcjsuvz] archive file ...\n");
- (void)fprintf(stderr, "\tar -r [-Tabcijsuvz] position archive =
file ...\n");
+ (void)fprintf(stderr, "\tar -r [-TcDjsuvz] archive file ...\n");
+ (void)fprintf(stderr, "\tar -r [-TabcDijsuvz] position archive =
file ...\n");
(void)fprintf(stderr, "\tar -s [-jz] archive\n");
(void)fprintf(stderr, "\tar -t [-Tv] archive [file ...]\n");
(void)fprintf(stderr, "\tar -x [-CTouv] archive [file ...]\n");
Index: ar.h
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- ar.h (revision 213478)
+++ ar.h (working copy)
@@ -43,6 +43,7 @@
#define AR_U 0x0200 /* only extract or update newer =
members.*/
#define AR_V 0x0400 /* verbose mode */
#define AR_Z 0x0800 /* gzip compression */
+#define AR_D 0x1000 /* insert members with dummy mtime, uid =
and gid */
=20
#define DEF_BLKSZ 10240 /* default block size */
=20
Index: write.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- write.c (revision 213478)
+++ write.c (working copy)
@@ -163,11 +163,22 @@
if (mtime !=3D 0 && bsdar->options & AR_U && sb.st_mtime <=3D =
mtime)
goto giveup;
=20
- obj->uid =3D sb.st_uid;
- obj->gid =3D sb.st_gid;
+ /*
+ * When modifier -D is specified, mtime and UID / GID from the =
file
+ * will be replaced with 0. This ensures that checksums will =
match=20
+ * for two archives containing the exact same files.
+ */
+ if (bsdar->options & AR_D) {
+ obj->uid =3D 0;
+ obj->gid =3D 0;
+ obj->mtime =3D 0;
+ } else {
+ obj->uid =3D sb.st_uid;
+ obj->gid =3D sb.st_gid;
+ obj->mtime =3D sb.st_mtime;
+ }
obj->md =3D sb.st_mode;
obj->size =3D sb.st_size;
- obj->mtime =3D sb.st_mtime;
obj->dev =3D sb.st_dev;
obj->ino =3D sb.st_ino;
=20
@@ -621,7 +632,10 @@
bsdar->options & AR_S) {
entry =3D archive_entry_new();
archive_entry_copy_pathname(entry, "/");
- archive_entry_set_mtime(entry, time(NULL), 0);
+ if (bsdar->options & AR_O)
+ archive_entry_set_mtime(entry, 0, 0);
+ else
+ archive_entry_set_mtime(entry, time(NULL), 0);
archive_entry_set_size(entry, (bsdar->s_cnt + 1) *
sizeof(uint32_t) + bsdar->s_sn_sz);
AC(archive_write_header(a, entry));
Thanks,
Erik
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