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From: John Gordon <gordon@panix.com>
Newsgroups: comp.lang.python
Subject: Re: ctypes - python2.7.3 vs python3.2.3
Date: Fri, 7 Sep 2012 19:04:13 +0000 (UTC)
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In <9a74$503e88dd$546bb230$30836@cache80.multikabel.net> Jan Kuiken <jan.kuiken@quicknet.nl> writes:

> >> uint32_t myfunction (char ** _mydata)
> >> {
> >>     char mydata[16];
> >
> >>     strcpy(mydata, "Hello Dude!");
> >
> >>     *_mydata = mydata;
> >
> >>     return 0;
> >> }
> >
> > mydata is an auto variable, which goes out of scope when myfunction()
> > exits.  *_mydata ends up pointing to garbage.

> I'm not completely sure, but i think this can be solved by using:

>      static char mydata[16];

That will solve the immediate problem, however it makes myfunction()
non-reentrant.

> (Btw.: I don't know why you use char ** _mydata, i would use
>         char * _mydata, but then again, i'm not very familiar with
>         ctypes)

He uses char **_mydata because he wants myfunction()'s caller to see the
new value of _mydata, which it wouldn't if it were just char *_mydata.

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"