On 04/06/2013 18:08, Lyle Hazelwood wrote:
>>> Line 9. *argv[i] should be argv[i]
>>
>> Yup. that's what they are looking for. argv[] is an array of
>> pointers to char.
>=20
> Just for fun, what does *argv[i] return, and why does it cause
> such nasty behavior?
> (Yes, I have the answers, but only after plugging it in to gcc)

It will segfault as it tries to print random memory.  A short snippet of
valgrind output illustrates this nicely:

david@lenny:~$ valgrind ./a.out
=3D=3D11548=3D=3D Memcheck, a memory error detector
=3D=3D11548=3D=3D Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward =
et al.
=3D=3D11548=3D=3D Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h=
 for
copyright info
=3D=3D11548=3D=3D Command: ./a.out
=3D=3D11548=3D=3D
=3D=3D11548=3D=3D Invalid read of size 1
=3D=3D11548=3D=3D    at 0x40250D8: __GI_strlen (mc_replace_strmem.c:284)
=3D=3D11548=3D=3D    by 0x407186E: vfprintf (vfprintf.c:1617)
=3D=3D11548=3D=3D    by 0x40783DF: printf (printf.c:35)
=3D=3D11548=3D=3D    by 0x8048401: main (in /home/david/a.out)
=3D=3D11548=3D=3D  Address 0x2e is not stack'd, malloc'd or (recently) free=
'd

For a hint at where the 0x2e comes from, consider what argv[0] contains
the way I ran it.

Note that the line from the challenge can also be correctly written as:

printf ("Argument #%d: '%s'\n", i, *(argv + i));

Pointers are fun.

David

--=20
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