Re: [PATCH] remaining steps for time64 switchover

[Rich Felker <dalias@libc.org>]

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On Tue, Oct 29, 2019 at 03:52:45PM -0400, Rich Felker wrote:
> On Sun, Oct 20, 2019 at 10:46:43PM -0400, Rich Felker wrote:
> > The attached patch series on top of present git master (commit
> > 9b2921bea1d5017832e1b45d1fd64220047a9802) should contain all changes
> > needed for fully working time64 on 32-bit archs, in a form that's
> > plausibly ready for commit (no makeshift hacks just to get things
> > demonstrably working). The one omission I'm aware of is what to do
> > with struct utmpx, which is not actually used at present in any libc
> > interfaces and thus not part of the ABI surface of libc. That will be
> > addressed in a separate thread.
> > 
> > Comments and basic testing are welcome at this point. It should be
> > possible to build for any of the 32-bit archs, but I have only tested
> > build for a few and only tested execution on i386 and sh.
> > 
> > Some useful checks for anyone wanting to help test, especially on the
> > more obscure archs:
> > 
> > [...]
> > 
> > - Anything look odd about time-related types? timeval/timespec members
> >   at positions that aren't naturally aligned?
> 
> I tested this on i386 (with low alignment requirement, only 4 bytes)
> with the attached program and it seems like I indeed got the padding
> slots as-intended on the ipc types. This should mean the adjacent
> explicit-padding members have no effect on other archs using the same
> changes but with natural alignment, which matches the intent. As usual
> mips and ppc are gratuitously different and seemed right to me but
> should perhaps be double-checked at some point. However since they
> have natural alignment the worst that could happen is leaving extra
> padding slots we don't need.

Attachment forgotten, here. Usage is to build against the appropriate
libc/headers and save output, then diff outputs as desired.

Rich


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#include <stddef.h>
#include <stdio.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/msg.h>
#include <sys/stat.h>

#define O(s,m) printf("offsetof(%s, %s)==%zd\n", #s, #m, offsetof(s,m))

int main()
{
	O(struct semid_ds, sem_perm);
	O(struct semid_ds, sem_otime);
	O(struct semid_ds, sem_ctime);
	O(struct semid_ds, sem_nsems);

	O(struct shmid_ds, shm_perm);
	O(struct shmid_ds, shm_segsz);
	O(struct shmid_ds, shm_atime);
	O(struct shmid_ds, shm_dtime);
	O(struct shmid_ds, shm_ctime);
	O(struct shmid_ds, shm_cpid);
	O(struct shmid_ds, shm_lpid);
	O(struct shmid_ds, shm_nattch);

	O(struct msqid_ds, msg_perm);
	O(struct msqid_ds, msg_stime);
	O(struct msqid_ds, msg_rtime);
	O(struct msqid_ds, msg_ctime);
	O(struct msqid_ds, msg_cbytes);
	O(struct msqid_ds, msg_qnum);
	O(struct msqid_ds, msg_qbytes);
	O(struct msqid_ds, msg_lspid);
	O(struct msqid_ds, msg_lrpid);

	O(struct stat, st_dev);
	O(struct stat, st_ino);
	O(struct stat, st_mode);
	O(struct stat, st_nlink);
	O(struct stat, st_uid);
	O(struct stat, st_gid);
	O(struct stat, st_rdev);
	O(struct stat, st_size);
	O(struct stat, st_blksize);
	O(struct stat, st_blocks);
	O(struct stat, st_atim);
	O(struct stat, st_mtim);
	O(struct stat, st_ctim);
}