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Re: /proc/*/cmdline corrupted
I've checked and on Linux (at least) xterm's command line is not
corrupted. From looking at the xterm code, it would appear that the X
libraries would have to be what is corrupting the command line. I
didn't look into the X library (XmParseCommand).
On Sun, Oct 16, 2011 at 5:31 PM, jan.kolar <email@example.com> wrote:
>> jc807j ? ?2668 ? ? 1 ?0 08:59 tty0 ? ? 00:00:00 xterm -e ssh server
> 80x72+285+0 -e ssh server
>> jc807j ? ?3004 ? ? 1 ?0 08:59 tty0 ? ? 00:00:00 xterm -e ssh server
>> 80x72-8+0 -e ssh server
>> jc807j ? ?2928 ?5852 ?0 09:12 ? ? ? ? ?00:00:00 xterm ?20000 +tb
>> The actual command lines for the 3 xterm processes are:
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72+285+0 -e ssh server
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72-8+0 -e ssh server
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb
> xterm calls XrmParseCommand() that
> "parses an (argc, argv) pair according to the specified option table ... and
> modifies the (argc, argv) pair to remove all recognized options."
> ? ? ? ? "-sl 20000 +tb -geometry 80x72+285+0"
> is properly removed
> and "-e ssh server" is moved to __argv[1 .. 3].
> Then __argv (respectively __argv for the shorter command) is assigned
> null pointer
> which results in the second "\0" in the od-output below.
> Either XrmParseCommand() does not update argc
> or the change does not propagate (how would that be possible?) to __argc.
> Therefore the command lines appear corrupted this particular way.
> /proc/*/cmdline ?uses a copy of __argc named __argc_safe
> which is hardly to be updated anyway.
> " ? for (int i = 0; i < __argc_safe; i++) "
> Funny enough, /proc/self/cmdline is likely to contain shortened version of
> " ? ? for (char **a = __argv; *a; a++) "
> [ pinfo.cc from cygwin 1.7.9-1 ]
>> I have verified that the "/proc/*/cmdline" is the source of the
>> corrupted information. ?"cmdline" from PID 2928 is:
>> jc807j@~>od -c /proc/2928/cmdline
>> 0000000 ? x ? t ? e ? r ? m ?\0 ?\0 ? 2 ? 0 ? 0 ? 0 ? 0 ?\0 ? + ? t ? b
>> 0000020 ?\0
> ?What does xterm on different platforms ?
> ?While concept of modifying own cmdline (In fact, __argv) is used very
> ?often to signal the process state down to the user,
> ?I was never thinking of modifying argc:
> ? ? main (int argc, char **argv)
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