[Octave-bug-tracker] [bug #40828] Exception handling: MException object functions

[John W. Eaton]

Follow-up Comment #12, bug #40828 (project octave):

@Guillaume: Yes, I forgot to include the small change I made to your
MException.m:

This part changes it to set hasBeenCaught to true if the constructor is called
with 2 arguments.  Maybe I should have used the value of the second argument,
but I just needed to set hasBeenCaught to true.


--- MException.m        2021-12-28 09:18:56.304544115 -0500
+++ MException.m        2021-12-28 09:57:26.453914848 -0500
@@ -47,11 +47,16 @@
   methods (Access = public)
 
     function this = MException (id, template, varargin)
-      if (nargin == 1 && isstruct (id))
-        # Matlab does not have this constructor. Used internally by last().
+      if ((nargin == 1 || nargin == 2) && isstruct (id))
+        # Matlab does not have this constructor. Used internally by
+        # last() and by the evaluator in constructing exception
+        # objects in CATCH blocks.
         this.identifier = id.identifier;
         this.message = id.message;
         this.stack = id.stack;
+        if (nargin == 2)
+          this.hasBeenCaught = true;
+        endif
       else
         if (nargin < 2 || nargout > 1)
           print_usage ();


I also needed this change to accept Octave's error identifiers that include
'-' characters:


--- MException.m        2021-12-28 09:18:56.304544115 -0500
+++ MException.m        2021-12-28 09:57:26.453914848 -0500
@@ -65,7 +70,10 @@
       if (! ischar (this.message) || (! isempty (this.message) && ! isrow
(this.message)))
         error ("MException: Message must be a row string.");
       endif
-      if (! isempty(this.identifier) && isempty
(regexp(this.identifier,'^([a-zA-Z]\w*)(:[a-zA-Z]\w*)+$')))
+      if (! isempty (this.identifier)
+          && isempty (regexp (this.identifier,
+
+                             
"^([A-Za-z][A-Za-z)-9_-]*)(:[A-Za-z][A-Za-z0-9_-]*)*$")))
         error ("MException: Invalid identifier.");
       endif
     endfunction


When we get this working it would probably be best to find a way to construct
the MException object without needing to evaluate a function so that Octave
will always correctly construct these objects even if the MException function
is shadowed by some user-defined function.  I mean, I assume that Matlab
doesn't call a user-defined MException constructor if it happens to appear
somewhere in the the path, right?

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