[Bug fortran/54878] New: libgfortran issues found by the Coverity scanner

["burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54878

             Bug #: 54878
           Summary: libgfortran issues found by the Coverity scanner
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org
                CC: jb@gcc.gnu.org, tkoenig@gcc.gnu.org


Sister bug to the FE PR 54599. The coverity scanner found the following
(potential) issues in libgfortran.


a) io/unix.c: Before calling mkstemps, one should set the umask - otherwise,
one might create a world-readable file in /tmp. As the Linux man page put it:

   The old behavior of creating a file with mode 0666 may be a security
   risk, especially since other UNIX flavors use 0600, and  somebody
   might overlook this detail when porting programs.

   More  generally,  the POSIX specification of mkstemp() does not say
   anything about file modes, so the application should make sure its
   file mode creation mask (see umask(2)) is set appropriately before
   calling mkstemp() (and mkostemp()).


b) io/unix.c: In fd_to_stream: Return value not checked for
  fstat (fd, &statbuf);


c) io/unit.c's filename_from_unit

  At (17): Calling function "unpack_filename(char *, char const *, int)"
  without checking return value (as is done elsewhere 10 out of 12 times).
  At (18): No check of the return value of "unpack_filename(filename, u->file,
  u->file_len)".
784      unpack_filename (filename, u->file, u->file_len);
785      return filename;


d) generated/iall_i1.c: Unreachable code:

220  len = GFC_DESCRIPTOR_EXTENT(array,dim);
221  if (len <= 0)
222    return;
...
326        if (len <= 0)
327          *dest = 0;


e) runtime/bounds.c: index_type count_0

At (3): Comparing "base" to null implies that "base" might be null.
228      if (base)
229        base = GFOR_POINTER_TO_L1 (base, kind);
...
CID 732652 (#1 of 1): Dereference after null check (FORWARD_NULL)At (10):
Dereferencing null pointer "base".
248      if (*base)
249        result ++;


f) io/list_read.c: Unreachable code in nml_query:

2432          p = write_block (dtp, endlen + 3);
2433            goto query_return;
2434          memcpy (p, &nmlend, endlen + 3);  /* <<< UNREACHABLE */

Additionally/Hence: the result "p" is never used.


g) io/intrinsics.c

CID 732515 (#1 of 1): Unchecked return value (CHECKED_RETURN)At (3): Calling
function "sseek(stream *, gfc_offset, int)" without checking return value (as
is done elsewhere 21 out of 26 times).

(Also not checked in io/file_pos.c's st_backspace.)

262 gf_ftell (int unit)
...
269    sseek (u->s, pos, SEEK_CUR);


h) io/inquire.c: inquire_via_unit

47      *iqp->exist = (iqp->common.unit >= 0
48                     && iqp->common.unit <= GFC_INTEGER_4_HUGE);

The latter is ways true as common.unit is of type GFC_INTEGER_4.


And some more.