Implement file locking in SQLite on Posix #1938
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slozier
approved these changes
Apr 4, 2025
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The file locking strategy in SQLite was basically Windows-oriented, with some provisions for limited-trust environment like Silverlight, WinRT, and Windows Mobile. These are obsolete but somebody repurposed the limited-trust strategy to work on Unix. This worked on Linux (sort of, shared locks were seemingly emulated in a way that only SQLite respected), but wasn't working at all on macOS.
This PR implements proper locking on Linux and macOS through a fcntl syscall via Mono.Unix. Locking on Windows is unchanged.
I resisted the temptation to start cleaning up the code (it is even badly formatted), because there would be no end to it, and it is better to replace it by a modern SQLite implementation in a longer run anyway.