[Python-Dev] before I open an issue re: posix.stat and/or os.stat

21 Feb 2019

      ...
...
...
import sys
sys.maxsize
9223372036854775807
import posix
posix.stat("/tmp/xxx")
My focus is AIX - and I believe I found a bug in AIX include files in
64-bit mode. I'll take that up with IBM and AIX support. However, this
issue might also be valid in Python3.

The following is from Centos, not AIX

Python 2.7.5 (default, Jul 13 2018, 13:06:57)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
posix.stat_result(st_mode=33188, st_ino=33925869, st_dev=64768L,
st_nlink=1, st_uid=0, st_gid=0, st_size=0, st_atime=1550742595,
st_mtime=1550742595, st_ctime=1550742595)
...
...
...
st=posix.stat("/tmp/xxx")
dev=st.st_dev
min=posix.minor(dev)
maj=posix.major(dev)
min,max
(0, <built-in function max>)
min
0
max
<built-in function max>
maj
253
posix.minor(dev)
0
posix.major(655536)
2560
posix.major(65536)
256
posix.major(256)
1
import os
os.major(256)
1
In AIX - 64-bit mode

Python 3.8.0a1+ (heads/master:e7a4bb554e, Feb 20 2019, 18:40:08) [C] on aix7
Type "help", "copyright", "credits" or "license" for more information.
...
...
...
import sys,os,posix
sys.maxsize
9223372036854775807
posix.major(256)
0
posix.major(65536)
1
posix.stat("/tmp/xxx")
os.stat_result(st_mode=33188, st_ino=12, st_dev=-9223371993905102841,
st_nlink=1, st_uid=202, st_gid=1954, st_size=0, st_atime=1550690105,
st_mtime=1550690105, st_ctime=1550690105)
AIX 32-bit:

root@x066:[/data/prj/python/git/python3-3.8.0.66]./python
Python 3.8.0a1+ (heads/master:e7a4bb554e, Feb 19 2019, 11:22:56) [C] on aix6
Type "help", "copyright", "credits" or "license" for more information.
...
...
...
import os,sys,posix
sys.maxsize
2147483647
posix.major(65536)
1
posix.stat("/tmp/xxx")
os.stat_result(st_mode=33188, st_ino=149, st_dev=655367, st_nlink=1,
st_uid=0, st_gid=0, st_size=0, st_atime=1550743517, st_mtime=1550743517,
st_ctime=1550743517)
To make it easier to view:

buildbot@x064:[/home/buildbot]cat osstat.c
#include 
#include 
#include 
#include 

main()
{
        dev_t dev;
        char *path = "/tmp/xxx";
        struct stat st;
        int     minor,major;

        lstat(path,&st);

        printf("size: %d\n", sizeof(st.st_dev));
        dev = st.st_dev;
        minor = minor(dev);
        major = major(dev);
        printf("%016lx %ld %ld\n",dev,dev, (unsigned) dev);
        printf("%d,%d\n",major,minor);
}

buildbot@x064:[/home/buildbot]OBJECT_MODE=32 cc osstat.c -o osstat-32 &&
./osstat-32
size: 4
00000000000a0007 655367 655367
10,7

And here is the AIX behavior (and bug - major() macro!)

buildbot@x064:[/home/buildbot]OBJECT_MODE=64 cc osstat.c -o osstat-64 &&
./osstat-64
size: 8
8000000a00000007 -9223371993905102841 7
0,7

The same on AIX 6 (above is AIX7) - and also with gcc:

root@x068:[/data/prj]gcc -maix64 osstat.c -o osstat-64 && ./osstat-64
size: 8
8000000a00000007 -9223371993905102841 42949672967
0,7
root@x068:[/data/prj]gcc -maix32 osstat.c -o osstat-32 && ./osstat-32
size: 4
00000000000a0007 655367 0
10,7
root@x068:[/data/prj]

So, the AIX 'bug' with the macro major() has been around for ages - but
ALSO setting the MSB of the st_dev.

+++++

Now my question:

Will this continue to be enough space - i.e., is the Dev size going to
be enough?

 +2042  #ifdef MS_WINDOWS
 +2043      PyStructSequence_SET_ITEM(v, 2,
PyLong_FromUnsignedLong(st->st_dev));
 +2044  #else
 +2045      PyStructSequence_SET_ITEM(v, 2, _PyLong_FromDev(st->st_dev));
 +2046  #endif

 +711  #define _PyLong_FromDev PyLong_FromLongLong

It seems so - however, Is there something such as PyUnsignedLong and is
that large enough for a "long long"? and if it exists, would that make
the value positive (for the first test).

posix.major and os.major will need to mask away the MSB and
posix.makedev and os.makedev will need to add it back.

OR - do I need to make the PyStat values "the same" in both 32-bit and
64-bit?

Puzzled on what you think is the correct approach.

Michael