Description

atime and ctime are problematic in tar entries - not all tar readers support them. GnuTarEntry and PaxTarEntry have been changed to not add these fields by default. The fields will still be preserved when reading, and a user may set them directly, but they will not be set on existing entries that didn't have them to start, or when converting from other entry types.

The behavior TarEntry.ModificationTime is unchanged. It is initialized to UtcNow for tar entries created with a constructor, and uses the file modification time for entries created from files.

Other minor fixes have been made to System.Formats.Tar to prioritize round-tripping of TarEntrys from read -> write without change.

cc @tmds

Version

.NET 10 Preview 5

Previous behavior

GnuTarEntry and PaxTarEntry would always add atime and ctime values.

New behavior

GnuTarEntry and PaxTarEntry only set atime and ctime if read from an entry that had them or the user explicitly set them.

Type of breaking change

• Binary incompatible: Existing binaries might encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
• Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code might require source changes to compile successfully.
• Behavioral change: Existing binaries might behave differently at run time.

Reason for change

Better compatibility with other tar readers, round-tripping tar files without modification.

Recommended action

No action required for most users.
If you require these fields to be set you can do so directly with GnuTarEntry.AccessTime, GnuTarEntry.ChangeTime, or PaxTarEntry(TarEntryType entryType, string entryName, IEnumerable<KeyValuePair<string, string>> extendedAttributes)- but know that this will create a tar that is not readable by many tar clients.

Feature area

Core .NET libraries

Affected APIs

System.Formats.Tar.GnuTarEntry
System.Formats.Tar.TarReader
System.Formats.Tar.TarWriter

Associated WorkItem - 437611