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From: Ken Brown <kbrown@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: chown: make sure ctime gets updated when necessary Date: Tue, 26 Jan 2021 14:37:27 +0000 (GMT) [thread overview] Message-ID: <20210126143727.2E40E385DC1A@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=b32f6dd40a2764aed1baec35da0a7512f3fbceb3 commit b32f6dd40a2764aed1baec35da0a7512f3fbceb3 Author: Ken Brown <kbrown@cornell.edu> Date: Mon Jan 25 21:05:37 2021 -0500 Cygwin: chown: make sure ctime gets updated when necessary Following POSIX, ensure that ctime is updated if chown succeeds, unless the new owner is specified as (uid_t)-1 and the new group is specified as (gid_t)-1. Previously, ctime was unchanged whenever the owner and group were both unchanged. Aside from POSIX compliance, this fix makes gnulib report that chown works on Cygwin. This improves the efficiency of packages like GNU tar that use gnulib's chown module. Previously such packages would use a gnulib replacement for chown on Cygwin. Diff: --- winsup/cygwin/fhandler_disk_file.cc | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/winsup/cygwin/fhandler_disk_file.cc b/winsup/cygwin/fhandler_disk_file.cc index 07f9c513a..5e58688b7 100644 --- a/winsup/cygwin/fhandler_disk_file.cc +++ b/winsup/cygwin/fhandler_disk_file.cc @@ -887,15 +887,18 @@ fhandler_disk_file::fchown (uid_t uid, gid_t gid) aclp, MAX_ACL_ENTRIES)) < 0) goto out; - if (uid == ILLEGAL_UID) - uid = old_uid; - if (gid == ILLEGAL_GID) - gid = old_gid; - if (uid == old_uid && gid == old_gid) + /* According to POSIX, chown can be a no-op if uid is (uid_t)-1 and + gid is (gid_t)-1. Otherwise, even if uid and gid are unchanged, + we must ensure that ctime is updated. */ + if (uid == ILLEGAL_UID && gid == ILLEGAL_GID) { ret = 0; goto out; } + if (uid == ILLEGAL_UID) + uid = old_uid; + else if (gid == ILLEGAL_GID) + gid = old_gid; /* Windows ACLs can contain permissions for one group, while being owned by another user/group. The permission bits returned above are pretty much
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