I've recently added a fairly simple error handler to an existing application. The error handler, connected to ON ERROR, just collects info about the error and dumps it into a table, then gives the user some choice about what to do.

In my simple testing, it works fine, but in some cases, it's causing a buffer overrun that's crashing VFP. The line where it crashes is LIST MEMORY. Here's the code up to and including a few lines after the crash:

LPARAMETERS tWhen, cWhere, nLine

LOCAL aErrorInfo[1]

AERROR(aErrorInfo)

* Log the data, including the call stack, into the
* ONERROR table. Also, construct a message to the user.

LOCAL cStackInfo, nStackLevels, aStackData[1], nStackLevel	

cStackInfo = ""
nStackLevels = ASTACKINFO(aStackData)
FOR nStackLevel = 1 TO m.nStackLevels
	cStackInfo = m.cStackInfo + ;
	             "  Level: " + TRANSFORM(aStackData[m.nStackLevel, 1]) + CHR(13) + CHR(10) + ;
	             "   File: " + aStackData[m.nStackLevel, 2] + CHR(13) + CHR(10) + ;
	             "   Module/Object: " + aStackData[m.nStackLevel, 3] + CHR(13) + CHR(10) + ;
	             "   Line: " + TRANSFORM(aStackData[m.nStackLevel, 5]) + ;
	             ": " + aStackData[m.nStackLevel, 6] + CHR(13) + CHR(10)
ENDFOR

LOCAL cOldSafety, cMemFile, cStatFile
cOldSafety = SET("Safety")
SET SAFETY OFF 
cMemFile = FORCEPATH("ListMemo.txt", SYS(2023))
LIST MEMORY TO (m.cMemFile) NOCONSOLE 
cStatFile = FORCEPATH("ListStatus.txt", SYS(2023))
LIST STATUS TO (m.cStatFile) NOCONSOLE 
SET SAFETY &cOldSafety

The one twist here is that this application is working with a bunch of VFP-based COM objects. They get instantiated pretty early, and in fact, I've seen at least one case where I can put an error in after that and I don't get the buffer overrun.

It appears that the difference may be whether I have READ EVENTS in effect. If I stick an error in right before or right after READ EVENTS, the error handler works as expected. If I introduce an error in code that will run with READ EVENTS in effect, I get the crash.

Anybody have any suggestions? For now, of course, I'm commenting that part of the code out, so that I can test other things, but I'd really like to have the memory and status info in the error log.

Tamar