[Octave-bug-tracker] [bug #54419] Failure in fread() index causes multiple error statements from get_size() try-catch

[Dan Sebald]

URL:
  <http://savannah.gnu.org/bugs/?54419>

                 Summary: Failure in fread() index causes multiple error
statements from get_size() try-catch
                 Project: GNU Octave
            Submitted by: sebald
            Submitted on: Wed 01 Aug 2018 04:14:32 PM UTC
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: GNU/Linux

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Details:

For changeset: 25709:02fbbde15308, try the following


octave:1> fn = "ramp10by11.dat";
octave:2> fid = fopen(fn, "w+");
octave:3> fwrite (fid, ones(10,1)*[1:11], "single");
octave:4> frewind (fid);
octave:5> x = fread (fid, [-10, -11], "single");
error: fread: negative value invalid as size specification
error: value on right hand side of assignment is undefined


Inside get_size() of file oct-stream.cc is the following test that is throwing
the error on the negative index:


        if (d < 0.0)
          ::error ("%s: negative value invalid as size specification",
                   who.c_str ());


Normally that ::error() variant is supposed to send control directly back to
the command line with error.  However, it looks as though the point where
get_size() is called is within a try-catch block:


  octave_value
  stream::read (const Array<double>& size, octave_idx_type block_size,
                oct_data_conv::data_type input_type,
                oct_data_conv::data_type output_type,
                octave_idx_type skip, mach_info::float_format ffmt,
                octave_idx_type& count)
  {
    octave_value retval;

    if (! stream_ok ())
      return retval;
[snip]
    try
      {
        get_size (size, nr, nc, one_elt_size_spec, "fread");
      }
    catch (const execution_exception&)
      {
        invalid_operation ("fread", "reading");

        return retval;
      }


As a result, the ::error() within get_size() doesn't act as expected, and a
second error message appears.




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