[Octave-bug-tracker] [bug #55599] print_usage() within subfunction results error

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?55599>

                 Summary: print_usage() within subfunction results error
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Tue 29 Jan 2019 08:00:17 AM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: Any

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Details:

Here is how to produce this error:

octave:1>  gradient (ones (4,5,3), 1, 1)
error: 'fullname' undefined near line 55 column 33
error: called from
    print_usage at line 55 column 16
    gradient>matrix_gradient at line 102 column 5
    gradient at line 74 column 35


and here is another simpler example:
first, create an Octave function file named "tmp.m":

$  cat tmp.m 
function tmp
##      print_usage()
        tmp1
end

function tmp1
        print_usage()
end


then, invoke this function "tmp" in Octave:

octave:2>  tmp
error: 'fullname' undefined near line 55 column 33
error: called from
    print_usage at line 55 column 16
    tmp>tmp1 at line 7 column 2
    tmp at line 3 column 2



The reason is that there is an useless variable named "fullpath",
and the variable "fullname" may be undefined if the line 41 in "print_usage.m"
has a false value:

$  grep fullpath -w -C3 -n /usr/share/octave/4.4.1/m/help/print_usage.m
37-    else
38-      error ("Octave:invalid-context", "print_usage: invalid function\n");
39-    endif
40:    fullpath = evalin ("caller", 'mfilename ("fullpath")');
41:    if (strcmp (fullpath(end-length(name)+1:end), name))
42:      fullname = [fullpath ".m"];
43-    endif
44-  elseif (! ischar (name))
45-    error ("Octave:invalid-input-arg",


Here is a possible patch for this bug:

--- a/scripts/help/print_usage.m
+++ b/scripts/help/print_usage.m
@@ -37,9 +37,9 @@
     else
       error ("Octave:invalid-context", "print_usage: invalid function\n");
     endif
-    fullpath = evalin ("caller", 'mfilename ("fullpath")');
-    if (strcmp (fullpath(end-length(name)+1:end), name))
-      fullname = [fullpath ".m"];
+    fullname = evalin ("caller", 'mfilename ("fullpath")');
+    if (strcmp (fullname(end-length(name)+1:end), name))
+      fullname = [fullname ".m"];
     endif
   elseif (! ischar (name))
     error ("Octave:invalid-input-arg",



After applying the above patch, the "undefined variable" error disappears, but
it would print some less useful information:

octave:4>  gradient (ones (4,5,3), 1, 1)
error: print_usage: 'matrix_gradient' not found
octave:4>  tmp
error: print_usage: 'tmp1' not found


This is because these subfunctions do not have their own docstrings.
Therefore, it seems that in this case it would better to invoke "print_usage"
with the corresponding "main function" name, just like "plotmatrix.m":

$  grep print_usage -w -C2 -n
/usr/share/octave/4.4.1/m/plot/draw/plotmatrix.m
73-
74-  if (nargin > 3 || nargin < 1)
75:    print_usage ();
76-  endif
77-
--
147-        break;
148-      else
149:        print_usage ("plotmatrix");
150-      endif
151-    endif
--
160-    Y = varargin{2};
161-  else
162:    print_usage ("plotmatrix");
163-  endif
164-


Below is some more possible patch:

diff -ur a/scripts/general/gradient.m b/scripts/general/gradient.m
--- a/scripts/general/gradient.m
+++ b/scripts/general/gradient.m
@@ -99,7 +99,7 @@
   endif
 
   if (nargin > 2 && nargin != nd + 1)
-    print_usage ();
+    print_usage ("gradient");
   endif
 
   ## cell d stores a spacing vector for each dimension
diff -ur a/scripts/plot/draw/reducepatch.m b/scripts/plot/draw/reducepatch.m
--- a/scripts/plot/draw/reducepatch.m
+++ b/scripts/plot/draw/reducepatch.m
@@ -197,7 +197,7 @@
              "FACES, second argument must be a matrix containing
VERTICES"]);
     endif
   else
-    print_usage ();
+    print_usage ("reducepatch");
   endif
 
   ## get reduction_factor
diff -ur a/scripts/statistics/quantile.m b/scripts/statistics/quantile.m
--- a/scripts/statistics/quantile.m
+++ b/scripts/statistics/quantile.m
@@ -406,7 +406,7 @@
 function inv = __quantile__ (x, p, method = 5)
 
   if (nargin < 2 || nargin > 3)
-    print_usage ();
+    print_usage ("quantile");
   endif
 
   if (isinteger (x) || islogical (x))






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