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From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: The mysterious error message
Message-ID: <1356@ttrdc.UUCP>
Date: Wed, 26-Nov-86 18:50:19 EST
Article-I.D.: ttrdc.1356
Posted: Wed Nov 26 18:50:19 1986
Date-Received: Thu, 27-Nov-86 01:57:52 EST
References: <1376@umd5>
Distribution: net
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 59
Keywords: consensus,account-name
Xref: mnetor comp.unix.questions:199 comp.unix.wizards:192

In article <1376@umd5>, cgs@umd5.UUCP writes:
>The consensus of opinion is the environment is getting trashed. I'm going
>to have to see what I can do with "dbx". It's strange that the environment
>is getting trashed when I don't pass **envp to the program, and I never
>attempt to do anything to the environment via a system() call.
>Since I've received a note that I'm not the only one to have noticed this,
>I'm including the following response I received for everyone's benefit:
>
>I've tried to do system("printenv"), but that too generates the error.
>So, I'm left with poking around with "dbx" until I find out what is
>going on.
>.. And hast thou slain the Jabberwock? ..

	You could try something like replacing system() with code which
	actually prints out the environment, since printenv may filter
	out garbage even if invoked directly via execlp() (I don't have
	BSD src handy here, but SysV env filters out environment garbage).
	E.g.:

extern char **environ;
#define system(stuff) \
	{ \
	    int ep=0; \
	    while(environ[ep]) \
		(void) printf("%s\n",environ[ep++]); \
	}

Question: does the code do any writing into its argument vector?  Or question-
able indexing upon automatic arrays?  On SysV on a 3B20, the following will
evoke your "00: not an identifier" diagnostic:

main(argc,argv)
char **argv;
{
	argv[argc+1]="00";	/* messing with invalid argument */
	(void) system("echo hello, world");
}

So will this, after a few iterations (eventually core dumping):

main()
{
	auto char *c[1];
	register int i=0;
	while (1) {
		c[--i]="00";	/* messing with stack */
		(void) system("echo hello, world");
	}
}

"hope this helps"
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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