[Bug libfortran/18958] eoshift segfaults when shifting off the end of an array

["Thomas dot Koenig at online dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-03-09 15:13 -------
$ cat eoshift.f90
  print *,eoshift((/1, 3/), 3)
end
$ gfortran eoshift.f90
$ ./a.out
Segmentation fault

This fails because the loop

      for (n = 0; n < len; n++)
        {
          memcpy (dest, src, size);
          dest += roffset;
          src += soffset;
        }

at line 146 ff. in eoshift0.c runs over its bounds
with the test case, because both n and len are of type index_type,
index_type is size_t, which is unsigned, and len is supposed to be -1
(so it's either 0xffffffff or 0xffffffffffffffff, depending on
wether size_t is 32-bit or 64-bit).

This has an "easy", one-letter fix:  typedef index_type as ssize_t
instad of size_t in libgfortran.h.

This fixes the bug and causes no testsuite regressions.  It also
has the potential to fix other, latent bugs like this one. This is
also a design decision which I feel should be discussed on
the fortran mailing list.

It would require some configuration work for libgfortran (not
all systems have ssize_t), which I don't feel I can handle
competently at the moment, so I won't submit a patch (at least
not now).

Thomas

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           What    |Removed                     |Added
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           Keywords|                            |wrong-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18958