Ah ha, the default locale in the Fedora docker image is LC_CTYPE=POSIX (without suffices like C.UTF-8), and any CJK characters like 风吹稻花香两岸 would fail. I guess that we can just propagate the error code up, that is, clean up local resources and then return the inner error code. Heap corruption is not only a bug. It is a potential security issue, leading to potential arbitrary memory access and arbitrary code execution. I am afraid there are more than one such issues in our code base. From: Stefan Dosinger <stefandoesinger(a)gmail.com> Sent: Monday, April 9, 2018 3:44 AM To: ??. ? Cc: wine-devel(a)winehq.org Subject: Re: Potential Heap Corrupt caused by unchecked return value   Hi, I am not an expert in our IMM or multi-language code, but from looking at the code there's no good way to handle the error from this place. I'd be curious why MultiByteToWideChar fails. My guess would be that the multi-byte string contains characters that are not valid in the selected language, and that XIM and Wine disagree on the validity of the input. Can you provide the language where this problem happens and what the input string passed to MultiByteToWideChar in this case is?