Hidden (?) error message on Windows

I have a small project (Xojo 2017R2, Windows 10) to which I recently made some minor changes.

After that the project still compiled without errors, but when started from the IDE, the (only) window
didn’t show up, but the IDE changed the “Start” to a “Resume” button after a few seconds.

Resuming the project, the program starts without errors or messages. It seems that the code
had stopped earlier at some point in assembly-code, which cannot be shown, of course. Also
the “log”-panel in the IDE did not show an error.

After building the process the program starts normally, although after a few seconds of showing
the “spinning wheel”.

As I couldn’t pinpoint an error-location, I tried the same project in the IDE on Linux (Ubuntu).

There immediately a runtime-exception message is shown, which points to the exact location of the
error: “Unrecognized format exception” in expression “'7.4%” (note the apostrophe), pointing to a part
of the columnwidths field of one of my two listboxes in the project. Very informative.
Although the text in this field in the IDE appeared to be correct (without the leading apostrophe),
even in the “editor” (pen-symbol near field), deleting and reentering the partial text cured the problem,
so it was probably caused by an invisible character in the string.

So my question now is: did the IDE on Windows 10 generate a similar but behind-the-scenes error message,
possibly in an error-log? I couldn’t find anything, searching the complete volume for error messages/logs.

what kind of project ?

A Windows 10 Desktop project. Very basic.

would need a sample that did this to examine

@Norman Palardy

A simple listbox, with multiple colomns, where the columnwidhts are given in percentages, with a similar
nonprintable (?) extra character would do, I guess.

The interesting part is more the differences in the way the errors are handled in Windows versus Linux.
Without the “clou” by the Linux errormessage it would have been difficult to find the cause of this problem.

DebugView is essential for working in Windows. It’s available for free from Microsoft: https://docs.microsoft.com/en-us/sysinternals/downloads/debugview It often leads to some very interesting discoveries - not just Xojo apps but everything else too.

Thank you, Bob.

In future, if such a situation arises again, I will have a look at the debugview method.

A small update, after trying Bob’s tip.

I still had a copy of my small project that exhibited the given error.

I used DebugView and started the (built) application.
It showed some errors but, unfortunately, none of which gave the very detailed info the error message on Linux did.

The most precise info in the errorlines that DebugView gave was :
[9312] Msg:[Unable to get property ‘substr’ of undefined or null reference - TypeError: Unable to get property ‘substr’ of undefined or null reference

It points in the right direction (“look at incorrect strings” …), but would have been still a long way to go …

So, if you have a working Linux distro, it might help in some situations to check your project there !
(might be true for Mac also, but I cannot test it).

[quote=347381:@J H Timmerman]
(might be true for Mac also, but I cannot test it).[/quote]
IMHO macOS gives the most useful stack traces & errors