From bug-octave-request at bevo dot che dot wisc dot edu  Thu Apr 19 10:07:11 2001
Subject: eval() tramples on __error_text__
From: Christoph Spiel <cspiel at hammersmith-consulting dot com>
To: bug-octave at bevo dot che dot wisc dot edu
Date: Thu, 19 Apr 2001 17:00:48 +0200

Hiya!

After John provided such a magnificent fix for
setting __error_text__ in a catch block, I have
looked at the behavior of the catch-string in
eval().  While

    try clear a; a; catch e=__error_text__; end_try_catch; e

now works,

    eval("clear a; a;", "e=__error_text__"); e

does not:

    octave:1> try clear a; a; catch e=__error_text__; end_try_catch; e
    e = `a' undefined near line 1 column 14

    octave:2> eval("clear a; a;", "e=__error_text__;"); e
    e = 
    octave:3> 


I cannot sully a fix yet, but after adding the
following three lines to "parse.y",


*** parse.y.orig        Wed Apr 18 20:31:12 2001
--- parse.y     Thu Apr 19 16:48:27 2001
***************
*** 3529,3534 ****
--- 3529,3539 ----
  
          buffer_error_messages = false;
          bind_global_error_variable ();
+ 
+         symbol_record *sym_rec = global_sym_tab->lookup("__error_text__");
+         std::string error_text(sym_rec->def().string_value());
+         bind_builtin_constant("error_text", error_text, true);
+ 
          unwind_protect::add (clear_global_error_variable, 0);
  
          eval_string (args(1), 0, parse_status, nargout);


the trouble spot reduces to either

(1) clearing '__error_text__' too early
    (Where?  Definitely not by the
    clear_global_error_variable pushed to the
    current frame.) or
(2) not transferring it into the namespace in
    which 'eval_string(args(1), ...)' lives,

because 'error_text' happily reports the last
error:

    octave:1> eval("clear a; a;", "e = __error_text__; f = error_text;"); e, f
    e = 
    f = `a' undefined near line 0 column 10

    octave:2> 



-chris

-- 
Christoph L. Spiel  <cspiel at hammersmith-consulting dot com>
Hammersmith Consulting,  web: www.hammersmith-consulting.com
Phone: +49-8022-662908, fax: +49-8022-662909



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