[Octave-bug-tracker] [bug #45752] strread causes "concatenation of different character string types" warning

[Lachlan Andrew]

URL:
  <http://savannah.gnu.org/bugs/?45752>

                 Summary: strread causes "concatenation of different character
string types" warning
                 Project: GNU Octave
            Submitted by: lachlan
            Submitted on: Fri 14 Aug 2015 02:44:33 AM GMT
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: None
             Assigned to: None
         Originator Name: Lachlan
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.0
        Operating System: GNU/Linux

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Details:

Running the code

warning("error")
strread ('1,1', '%d', 'delimiter', ',')

produces the error:  "error: concatenation of different character string types
may have unintended consequences".

The warning is normally suppressed, and so I didn't expect to get this error.

I want to debug Matlab code that produces a warning on Octave but an error on
Matlab, which is why I turned warnings into errors.  However, the strread
warning prevented me reaching the troublesome code.

The work-around is clear (only turn a specific warning into an error), but I
would like to fix the bug.  I see two options:

1. Make 'warning("error")' only convert warnings to errors if the warning is
not suppressed at the time the command is issued.  It is easy to write
'warning("error", "all")' if that is desired.  This seems to obey the
principle of least surprise.

2. Fix the code in strread (and possibly elsewhere) to avoid harmless
warnings.  This seems cleaner, but adds to code bloat, and takes a slight
performance hit -- strread is already too slow IMHO. 

I prefer option 1, but want input before writing the patch.

A related issue: it is not clear how to undo the effect of 'warning("error")'.
 I had to quit Octave and restart.  That is a bug in the documentation.




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