[PATCH] iconvconfig: Fix multiple issues

[Florian Weimer]

* Siddhesh Poyarekar via Libc-alpha:

> It was noticed on big-endian systems that msgfmt would fail with the
> following error:
>
> msgfmt: gconv_builtin.c:70: __gconv_get_builtin_trans: Assertion `cnt < sizeof (map) / sizeof (map[0])' failed.
> Aborted (core dumped)
>
> This is only seen on installed systems because it was due to a
> corrupted gconv-modules.cache.  iconvconfig had the following issues
> (it was specifically freeing fulldir that caused this issue, but other
> cleanups are also needed) that this patch fixes.
>
> - Add prefix only if dir starts with '/'
> - Use stpcpy instead of mempcpy so that the directory string is NULL
>   terminated
>
> - Do not free fulldir because it is used later while writing out the
>   gconv-modules.cache file.

I suggest to use asprintf.  This code is hardly performance critical,
and asprintf avoids such bugs.

I expect that static analysis tools can detect the missing free calls,
so I think we should still free those allocations.

Thanks,
Florian