Re: [Pythondialog-users] Repost: Crash! dialog.PythonDialogErrorBeforeExecInChildProcess - Please help to debug.

[Andy D. <an...@no...>]

On 9 Jan 2012, at 06:59, Jose Mari wrote:

> I think that in last instance pythondialog runs a shell with dialog cmd.
> 
> In function  _call_program(self, redirect_child_stdin, cmdargs,
> **kwargs) exits the exec command:
> os.execve(self._dialog_prg, arglist, new_environ)
> 
> Try to print the complete line call and test it in a bash shell.

Thanks for the advice.  In the documentation, I found that there was a suggested 'debugging' block of text that caused the command to be written out.  

                import commands
                
                envvar_settings_list = []

                if new_environ.has_key("DIALOGRC"):
                     envvar_settings_list.append(
                         "DIALOGRC='%s'" % new_environ["DIALOGRC"])

                for var in _dialog_exit_status_vars.keys():
                    varname = "DIALOG_" + var
                    envvar_settings_list.append(
                        "%s=%s" % (varname, new_environ[varname]))

                envvar_settings = string.join(envvar_settings_list, " ")

                file("command.debug", "wb").write(
                    envvar_settings +
                    string.join(map(commands.mkarg, arglist), ""))
                os.execve(self._dialog_prg, arglist, new_environ)

When it works ok, I get useful stuff in the output file :

DIALOG_OK=0 DIALOG_HELP=5 DIALOG_EXTRA=4 DIALOG_ESC=2 DIALOG_ERROR=3 DIALOG_CANCEL=1 '/usr/bin/dialog' '--backtitle' 'Welcome to xxxxx' '--menu' 'Where would you like to go today ?' '15' '60' '7' 'AddHost' 'Add Host to System' 'AddCheck' 'Add Check to Host' 'Logout' 'Log out of Shell'

But when I try to build a menu of options from the database as described in my original mail at the top of the thread, the output file is made blank.

-rw-r--r--  1 andy andy    0 Jan 10 17:31 command.debug



On 9 Jan 2012, at 08:18, Peter Åstrand wrote:

> Try running "strace -f" on the entire application.


This is what looks to happen at the time of the crash :

$ strace -f python xxshell.py  1
[...]
[pid 20299] fstat(6, {st_mode=S_IFREG|0644, st_size=2477, ...}) = 0
[pid 20299] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f5494054000
[pid 20299] read(6, "\321\362\r\nW\313\27Mc\0\0\0\0\0\0\0\0\3\0\0\0@\0\0\0sF\0\0\0d\0"..., 4096) = 2477
[pid 20299] fstat(6, {st_mode=S_IFREG|0644, st_size=2477, ...}) = 0
[pid 20299] read(6, "", 4096)           = 0
[pid 20299] close(6)                    = 0
[pid 20299] munmap(0x7f5494054000, 4096) = 0
[pid 20299] close(4)                    = 0
[pid 20299] open("command.debug", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 4
[pid 20299] fstat(4, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
[pid 20299] close(4)                    = 0
[pid 20299] exit_group(127)             = ?
Process 20296 resumed
Process 20299 detached
<... wait4 resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 127}], 0, NULL) = 20299
--- SIGCHLD (Child exited) @ 0 (0) ---
write(2, "Traceback (most recent call last"..., 35Traceback (most recent call last):
) = 35
write(2, "  File \"monshell.py\", line 126, "..., 44  File "monshell.py", line 126, in <module>
) = 44
open("monshell.py", O_RDONLY)           = 5
fstat(5, {st_mode=S_IFREG|0644, st_size=3578, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f5494054000
read(5, "import sys, os, os.path, time, s"..., 4096) = 3578
write(2, "    ", 4    )                     = 4
write(2, "if __name__ == \"__main__\": main("..., 34if __name__ == "__main__": main()
) = 34
close(5)                                = 0


Any ideas ?

Andy