FileLock encounters a runtime error when the path of the locked file is long #277
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abertelrud
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…is long FileLock constructs the name of the lock file based on the path of the file being locked. When this path is very long, the name of the constructed lock file exceeds `NAME_MAX` (or more specifically the directory entry name length limit of the file system on which the directory that contains it resides, but `NAME_MAX` is a decent approximation on modern file systems commonly in use). This change truncates it to `NAME_MAX` UTF-8 bytes (starting from the end), rounding down to avoid splitting Unicode scalars (but making no effort to avoid splitting clusters, since they don't affect the validity of the filename). Another possible refinement would be to also include a hash of the elided part of the filename — in the interest of avoiding complexity this implementation doesn't do that, and it's not clear that it's needed given that 255 (the common value of `NAME_MAX`) usually results in a unique enough name in any practical circumstances. rdar://87471360
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@abertelrud @tomerd this seems to have regressed the windows build: https://ci-external.swift.org/job/oss-swift-windows-toolchain-x86_64-vs2019/619/console |
compnerd
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This fixes multiple issues with the file locking implementation on Windows. `AbsolutePath.root` is meaningless on Windows - there is no concept of a singular root on Windows, instead you have have 26 individual roots - A-Z. Stripping the count of characters for the root path leaves us with an invalid path string as the root drives have been stripped. The next character is an invalid character on most file systems, and so we must replace `:`. Instead of using a `MAX_NAME` to compute a length of the ARC, enforce a limit for the complete path (though an ARC would be limited to 255 codepoints on NTFS). This incidentally also corrects the emitted path, previous path computation left us with the file in PWD.
compnerd
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Jan 13, 2022
This fixes multiple issues with the file locking implementation on Windows. `AbsolutePath.root` is meaningless on Windows - there is no concept of a singular root on Windows, instead you have have 26 individual roots - A-Z. Stripping the count of characters for the root path leaves us with an invalid path string as the root drives have been stripped. The next character is an invalid character on most file systems, and so we must replace `:`. Instead of using a `MAX_NAME` to compute a length of the ARC, enforce a limit for the complete path (though an ARC would be limited to 255 codepoints on NTFS). This incidentally also corrects the emitted path, previous path computation left us with the file in PWD.
compnerd
added a commit
to compnerd/swift-tools-support-core
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Jan 13, 2022
This fixes multiple issues with the file locking implementation on Windows. `AbsolutePath.root` is meaningless on Windows - there is no concept of a singular root on Windows, instead you have have 26 individual roots - A-Z. Stripping the count of characters for the root path leaves us with an invalid path string as the root drives have been stripped. The next character is an invalid character on most file systems, and so we must replace `:`. Instead of using a `MAX_NAME` to compute a length of the ARC, enforce a limit for the complete path (though an ARC would be limited to 255 codepoints on NTFS). This incidentally also corrects the emitted path, previous path computation left us with the file in PWD.
compnerd
added a commit
to compnerd/swift-tools-support-core
that referenced
this pull request
Jan 13, 2022
This fixes multiple issues with the file locking implementation on Windows. `AbsolutePath.root` is meaningless on Windows - there is no concept of a singular root on Windows, instead you have have 26 individual roots - A-Z. Stripping the count of characters for the root path leaves us with an invalid path string as the root drives have been stripped. The next character is an invalid character on most file systems, and so we must replace `:`. Instead of using a `MAX_NAME` to compute a length of the ARC, enforce a limit for the complete path (though an ARC would be limited to 255 codepoints on NTFS). This incidentally also corrects the emitted path, previous path computation left us with the file in PWD.
abertelrud
pushed a commit
that referenced
this pull request
Jan 13, 2022
This fixes multiple issues with the file locking implementation on Windows. `AbsolutePath.root` is meaningless on Windows - there is no concept of a singular root on Windows, instead you have have 26 individual roots - A-Z. Stripping the count of characters for the root path leaves us with an invalid path string as the root drives have been stripped. The next character is an invalid character on most file systems, and so we must replace `:`. Instead of using a `MAX_NAME` to compute a length of the ARC, enforce a limit for the complete path (though an ARC would be limited to 255 codepoints on NTFS). This incidentally also corrects the emitted path, previous path computation left us with the file in PWD.
compnerd
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Jan 14, 2022
TSCBasic: repair the Windows build after #277
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FileLock constructs the name of the lock file based on the path of the file being locked. When this path is very long, the name of the constructed lock file exceeds
NAME_MAX(or more specifically the directory entry name length limit of the file system on which the directory that contains it resides, butNAME_MAXis a decent approximation on modern file systems commonly in use).This change truncates it to
NAME_MAXUTF-8 bytes (starting from the end), rounding down to avoid splitting Unicode scalars (but making no effort to avoid splitting clusters, since they don't affect the validity of the filename). Another possible refinement would be to also include a hash of the elided part of the filename — in the interest of avoiding complexity this implementation doesn't do that, and it's not clear that it's needed given that 255 (the common value ofNAME_MAX) usually results in a unique enough name in any practical circumstances.rdar://87471360