To follow up from yesterday evening, now that I'm back at work:
The code in question is a FOR ... ENDFOR loop that iterates an array,
with the loop limiting value being the number of rows in the array,
and there is nothing within that loop that removes or adds rows or
columns to the array.
It's just:
FOR m.x = 1 TO ALEN(THISFORM.oMail.aSortList,1)
thekey = THISFORM.oMail.aSortList(m.x,10) && "array dimensions invalid"
** More inoffensive code here.
ENDFOR
As I've said, I can't reproduce this error myself but I've seen it
reported by my error handler twice in two days. So I don't know if
the iteration failed on the first row or some later row of the array.
As I mentioned earlier, my initial assumption that the array was
supposed to have 5 columns was incorrect, because I was looking at
the wrong control.
I've now verified that in this case, when the problem code executes,
this array can only contain 10 columns:
1. It is a predefined property of the oMail object (based on the
Custom class, and defined in a .prg file) and is DIMENSIONed as (1)
at the outset.
2. It is then populated by a SELECT [10 specified fields] FROM
[variable table/cursor] ... INTO ARRAY expression with no WHERE clause.
3. Although the name of the FROM table or cursor is variable, the
specified fields are not, and the expression does not use AS clauses
to change the names of the result fields or supply default values for
them. Therefore, if a specified field did not exist in the FROM
table, an error would be generated at that point. No such error occurs.
4. It is not possible for the FROM table to contain no records when
the offending code executes, because in that case the code that
generates the FROM table would display a message for the user stating
that the query produced no results and all of the related controls on
the form would be disabled. As a result, the method containing the
SELECT ... INTO ARRAY expression would not be called, the list
control's array rowsource would contain no records, and the list
control's sort method, where the error occurs, would not be called.
So I am confident that the array can only have 10 columns (no more
and no less) at the point where the error is generated.
Thus the only "possible" sources of an "array dimensions invalid"
error, if the error did indeed occur on the line indicated by the
trace, would be:
1. The SELECT ... INTO ARRAY expression somehow generated fewer
columns than were specified in its field list.
2. The user was somehow able to induce one of the disabled GUI
controls to somehow call the sort method when there was no data to sort.
3. ALEN() returned an incorrect result as to the number of rows in
the array during the iteration loop.
All of those things should be impossible.
The third possibility is that the trace provided by ASTACKINFO() is
wrong. In my application I frequently do see very strange things with
error traces, such as several levels of code that should be in the
stack not being reported. I have also seen, in the debugger, that
errors don't necessarily "surface" immediately and the line of code
that generates them may not be the line on which the debugger stops.
There could also be something wrong with my assumptions regarding how
to read a trace. In the case of the issue I've been talking about,
the trace contains the following lines:
Level: 5 Program File: c:\cil data 2\genmaillst.sct Module/Object:
genmaillst.listdisplay.resortlistbox Source File: c:\cil data
2\genmaillst.sct Line Number: 86 Line Contents: thekey =
THISFORM.oMail.aSortList(x,10)
Level: 6 Program File: c:\stic foxpro framework\base
classes\sticbase.vct Module/Object:
genmaillst.listdisplay.error Source File: c:\stic foxpro
framework\base classes\sticbase.vct Line Number: 23 Line Contents:
DO FinalSTICError WITH 0, LINENO(1), theprogram, MESSAGE(1), ""
I read this as: "When the line of code at Level 5 was executed, the
ERROR() method of the object that contains that code was triggered,
as shown in Level 6. Therefore, the error occurred in the stated line
of code in Level 5."
Of course, the way to handle this is to add code to test the size of
the array before trying to iterate it, which I have now done. But I
am still at a loss to understand how the error could occur.
Thanks.
Ken
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