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Re: [Bug-tar] Problem with fstatat on AIX 7.1

From: Kevin Brott
Subject: Re: [Bug-tar] Problem with fstatat on AIX 7.1
Date: Wed, 31 Aug 2011 19:35:55 -0700

On Wed, Aug 31, 2011 at 17:34, Paul Eggert <address@hidden> wrote:
On 08/31/11 07:06, Kevin Brott wrote:
> If we do not use fstatat then tar builds and passes almost all of the checks (only the two sparse file ones fail).
> If we use fstatat, then almost all of the checks fail - because the resulting binary is dropping zero-byte files into the archives, and doesn't function.
> So either there is a bug or enough of a fundamental difference in the way AIX 7.1's new fstatat call works, that it's not usable with the way the existing GNU tar code is trying to use it.

It semmed pretty clear there is a bug there.
Unfortunately, the test program does not seem to expose the bug.

How about this test program instead?  Please run it in a directory
where conftest.file has been created via "echo xxx >conftest.file".

If this test program works on AIX 7.1, can you modify it in a minor
way so that it correctly exposes the AIX bug?  There must be some
way to do it, since 'tar' is doing it.

 #include <fcntl.h>
 #include <sys/stat.h>

 main (void)
   struct stat a;
   struct stat b;
   int fd = open (".", O_RDONLY);

   if (fd < 0)
     return 10;
   if (fstatat (fd, "conftest.file", &a,
       != 0)
     return 1;
   if (lstat ("conftest.file", &b) != 0)
     return 2;
   if (a.st_size != b.st_size) return 3;
   if (a.st_dev != b.st_dev) return 4;
   if (a.st_ino != b.st_ino) return 5;
   if (a.st_mode != b.st_mode) return 6;
   if (a.st_nlink != b.st_nlink) return 7;
   if (a.st_uid != b.st_uid) return 8;
   if (a.st_gid != b.st_gid) return 9;
   /* Don't check time members, to avoid caching issues.  */
   return 0;

$ echo xxx > conftest.file
$ cat conftest.file
$ xlc -o test source.c
$ ./test ; echo $?
$ truss -f ./test
12058888: execve("./test", 0x2FF22AA4, 0x200132A8)       argc: 1
12058888: 16908635: kopen(".", O_RDONLY)                        = 3
12058888: 16908635: statxat(3, "conftest.file", 0x2FF22910, 76, 01) = 0
12058888: 16908635: statx("conftest.file", 0x2FF22988, 76, 01) = 0
12058888: 16908635: kfcntl(1, F_GETFL, 0x2FF22FFC)      = 67110914
12058888: 16908635: kfcntl(2, F_GETFL, 0x2FF22FFC)      = 67110914
12058888: 16908635: _exit(0)

I'm going to rebuild the non-working version of tar and the mostly-working version and have them both create a two-file archive and truss both runs.
Maybe someone less clueless than I will be able to see where the failure is.

# include <stddisclaimer.h>
/* Kevin  Brott <address@hidden> */

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