Hi,
When build in 32-bit, we have an alert “ThreadAccessingUIException” (if we access UI in a Thread) before the app crash. In 64-bit, no alert and the application hang, then we don’t know why.
Is it a bug or did I miss something ?
Sounds like a bug with the 64-bit build. File a feedback.
Thomas… It has not been possible to access the UI from a thread since 2013 or so.
If I read the OP’s post correctly, he is aware of that. He wants to know why no error message appeared when running in 64-bit.
Would need a bug report with a sample
I just did a few quick tests & definitely get ThreadAccessingUI Exceptions in 64 bit when debugging
Need to build this & try runtime
Yes I know we can’t access UI from a thread 
. In Debug, Xojo show the line where we access the UI, but in a build 64-bit application, it doesn’t display anything and the application is hanged without any alert dialog. If build in 32-bit we see an alert with the Quit button and the app quit when we click it.
A guys report me a bug that the application doesn’t respond (hang), its system is set to Japanese and he told me he think it is the problem. My app isn’t localized in Japanese and I don’t see why it could cause the problem. Then after some emails with him I suppose it’s a ThreadAccessUI.
I built a 32-bit and send it to him, I’m waiting for his answer.
Michel, on dit bien “hang” en Anglais quand une application est fige ?
Thank you Norman, I forgot to say my app are built for Mac with the last Xojo version.
C’est bien ça 
Merci Michel.
I’m happy to point out the problem of ThreadAccessUI in 64-bit but it’s not the problem. The guy answered me that the app works in 32-bit. And it seems I didn’t well understand, in 64-bit the app doesn’t hang but quit without any alert.
Then there is another problem in 64-bit.
It’s a good things that Xojo allow use debug app Free. As my source code are downloadable, I sometimes ask people to install Xojo and run my source in Debug mode. They just have to click the Run button and send me screencapture of the alert bug in Debug mode. I’ll ask him to do so.
It seems that the trouble in the 64-bit build comme from GetTextEncoding(&hEC) , (“MacInuit”).
The user who report the bug is under Sierra, I’m under El Capitan.
[code]Dim TypeEncod as TextEncoding
TypeEncod = GetTextEncoding(&hEC)
MsgBox “’” + TypeEncod.internetName +"’" + EndOfLine + (Cstr(TypeEncod.internetName = “”)) ’ Result ‘’ and True , It is an empty string = “”.[/code]
It is “MacInuit”. I think I found the name in a list with all the encodings name in the Xojo Help long time ago, but I didn’t reach to find this list again.
My program read email and search the encoding in a array I make with a lot of encoding.
I remove GetTextEncoding(&hEC) form my array and the guy told me the 64-bit version doesn’t crash anymore.