[Toybox] [df] percentage different from GNU df

[Roy Tam]

Hello,

2012/11/9 Rob Landley <rob at landley.net>:
> On 10/28/2012 10:50:50 PM, Roy Tam wrote:
>>
>> Hello,
>>
>> I noticed that toybox df shows different percentage from GNU df.
>> GNU df calculates percentage by used/(used+free) while toybox use
>> (blocks-free)/blocks.
>> (which one is better by the way?)
>
>
> According to posix-2008:
>
>> <percentage used>
>>
>> The percentage of the normally available space that is currently allocated
>> to all
>> files on the file system. This shall be calculated using the fraction:
>>   <space used>/( <space used>+ <space free>)
>> expressed as a percentage. This percentage may be greater than 100 if
>> <space free> is
>> less than zero. The percentage value shall be expressed as a positive
>> integer, with
>> any fractional result causing it to be rounded to the next highest
>> integer.
>
>
> The "space used" and "space free" entries are the used/available displayed
> in columns 3 and 4. The "any fractional result" implies that you do
> something like:
>
>   pct=(used*100)/(used+free)
>   if (pct*(used+free) != (used*100)) pct++;
>
> (Except all with 64 bit math so overflow sucks less.)
>
>
>> toybox$ ../busybox/busybox df
>> Filesystem           1K-blocks      Used Available Use% Mounted on
>> udev                     10240         0     10240   0% /dev
>> tmpfs                    12456       160     12296   1% /run
>> /dev/disk/by-uuid/4277274d-e9a1-42ff-a247-b75bde522deb
>>                        1913244   1151656    664400  63% /
>> tmpfs                    24912         0     24912   0% /run/shm
>
>
> 160/(160+12296.0)
> 0.012845215157353885
>
> Not doing the pedantic rounding up.
>
>
>> toybox$ df
>> Filesystem           1K-blocks      Used Available Use% Mounted on
>> rootfs                 1913244   1151656    664400  64% /
>> udev                     10240         0     10240   0% /dev
>> tmpfs                    12456       160     12296   2% /run
>> /dev/disk/by-uuid/4277274d-e9a1-42ff-a247-b75bde522deb
>>                        1913244   1151656    664400  64% /
>> tmpfs                    24912         0     24912   0% /run/shm
>
>
> Doing the pedantic rounding up.
>
>
>> toybox$ ./toybox df
>> Filesystem      1K-blocks       Used Available Use% Mounted on
>> tmpfs               24912          0     24912   0% /run/shm
>> /dev/sda1         1913244    1151656    664400  66% /
>> tmpfs               12456        160     12296   2% /run
>> udev                10240          0     10240   0% /dev
>
>
> Showing used as a percentage of 1K-blocks, ignoring "available" altogether.
>
> Right, I fixed it to match what the standard requires, which seems to be
> what upstream is doing.
>

I'm now hitting segfault with hg head.

toybox$ CFLAGS="-O0 -g" make
scripts/make.sh
Make generated/config.h from .config.
Extract configuration information from toys/*.c files...
Generate headers from toys/*/*.c...
generated/newtoys.h
generated/globals.h
generated/help.h
Extract help text from Config.in.
Library probe...
Compile toybox...
toybox$ gdb --args ./toybox_unstripped df
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/roy/toybox/toybox_unstripped...done.
(gdb) r
Starting program: /home/roy/toybox/toybox_unstripped df
Filesystem      1K-blocks       Used Available Use% Mounted on

Program received signal SIGSEGV, Segmentation fault.
0xb7e867a4 in vfprintf () from /lib/i386-linux-gnu/i686/cmov/libc.so.6
(gdb) bt
#0  0xb7e867a4 in vfprintf () from /lib/i386-linux-gnu/i686/cmov/libc.so.6
#1  0xb7e87270 in vprintf () from /lib/i386-linux-gnu/i686/cmov/libc.so.6
#2  0x0804ce44 in xprintf (format=0x805c445 "%s% *ld % 10ld % 9ld %
3ld%% %s\n") at lib/lib.c:152
#3  0x08051c78 in show_mt (mt=0x806b8b0) at toys/posix/df.c:94
#4  show_mt (mt=0x806b8b0) at toys/posix/df.c:49
#5  0x08051db6 in df_main () at toys/posix/df.c:159
#6  0x0804b3b2 in toy_exec (argv=0xbffffd78) at main.c:104
#7  0x0804b3ed in toybox_main () at main.c:118
#8  0x0804b3b2 in toy_exec (argv=0xbffffd74) at main.c:104
#9  0x0804b3ed in toybox_main () at main.c:118
#10 0x0804b14a in main (argc=2, argv=0xbffffd74) at main.c:159
(gdb) frame 2
#2  0x0804ce44 in xprintf (format=0x805c445 "%s% *ld % 10ld % 9ld %
3ld%% %s\n") at lib/lib.c:152
152             vprintf(format, va);
(gdb) print *va
$1 = 139 '\213'
(gdb) list
147     void xprintf(char *format, ...)
148     {
149             va_list va;
150             va_start(va, format);
151
152             vprintf(format, va);
153             if (ferror(stdout)) perror_exit("write");
154     }
155
156     void xputs(char *s)
(gdb) print va
$2 = (va_list) 0xbffffae4 "\213\271\006\b\024"
(gdb)


> Thanks for the heads up,
>
> Rob