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From: w6b7rk5yu4mt25v3 <w6b7rk5yu4mt25v3@protonmail.com>
To: "cygwin@cygwin.com" <cygwin@cygwin.com>,
	"cygwin-developers@cygwin.com" <cygwin-developers@cygwin.com>
Subject: I discovered the problems why the program I'm trying to port crashed
Date: Sun, 19 Feb 2023 16:56:15 +0000	[thread overview]
Message-ID: <bEc_juo0ZomxwHLHf1mKfbz_S9hMzlkUU691bG-cOPnyCDtaXjdjxwpMgZbbxq0ljP1LU4qJGYOr2IMwKRBmNzsU5bEqovMtZ37aqQOEUXY=@protonmail.com> (raw)

Quoted from https://cygwin.com/pipermail/cygwin-cvs/2020q3/014516.html:

"The file mapping will be only a single page, 4K, and since 64 bit systems don't support the AT_ROUND_TO_PAGE flag, the remainder of the 64K slot will result in a SEGV when accessed."

"The justification is that there's very likely no application actually utilizing the map beyond EOF, and we know that all bytes beyond EOF are set to 0 anyway."

Unfortunately, the application I'm trying to port do exactly that. If you set JIT_PAGE_SIZE to 64k (same as PAGE_SIZE) to satisfy mprotect then it will expect the whole 64k to be accessible. On other systems, no problems. On Cygwin, crashed with segmentation fault. I was right. Not the application's bug, but Cygwin's quirk (I called it as a quirk but not a bug, because it's a limitation of the platform).

Goodbye. It's better to use WSL directly than messing with Cygwin nowadays.

Sent with Proton Mail secure email.

                 reply	other threads:[~2023-02-20 10:34 UTC|newest]

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