Re: execv and then socket: "operation not permitted"

[Eric Hoffman <clallosy at gmail dot com>]

Thanks for the help! 

That's about the only significant change in about 37000 lines of C
code of a legacy application dating back to 1998... quite a testimony
to both the original programmer (not me!) skills and Cygwin
conformance to standards.

Cheers,

Eric


On Tue, 11 Jan 2005 13:20:15 +0100, Corinna Vinschen
<corinna-cygwin@cygwin.com> wrote:
> On Jan 10 22:54, Eric Hoffman wrote:
> > On Sun, 9 Jan 2005 13:19:53 +0100, Corinna Vinschen wrote:
> > > Could you please prepare a short testcase, only containing the
> > > necessary lines to reproduce the problem?
> >
> > I have attached 2 files to reproduce the problem. It is linked to the
> > putenv() call and the env variable then being reset.
> 
> Thanks for the testcase.
> 
> >       strcpy(fooflags,"fooflags=1");
> >       putenv(fooflags);
> >       *fooflags = '\0'; /* remove from environment after all */
> 
> Oh well.  What happens is that your empty string results in a fatal
> change in the Win32 environment propagated to the child application.
> A Win32 environment consists of a long string of \0-terminated strings.
> The end of the environment is indicated by a second \0, like this:
> 
>  "a=b\0c=d\0e=f\0\0"
> 
> By setting one of the strings to \0 as you do, the propagated environment
> contains an early \0:
> 
>  "\0\0c=d\0e=f\0\0"
> 
> The result is that the propagated Win32 environment is actually empty.
> Missing $PATH and $SYSTEMROOT are fatal and explain the socket problem
> you encountered.
> 
> This is a bug in Cygwin insofar as Cygwin should not allow to propagate
> empty strings to the child application.  I'm preparing a patch right now.
> In the meantime, don't do that.  Replace
> 
>  *fooflags = '\0';
> 
> by
> 
>  unsetenv ("fooflags");
> 
> NB: The use of setenv/unsetenv is preferrable over using putenv anyway.
> 
> 
> Corinna
> 
> --
> Corinna Vinschen                  Please, send mails regarding Cygwin to
> Cygwin Project Co-Leader          mailto:cygwin@cygwin.com
> Red Hat, Inc.
> 
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