New in version 3.24.
When using the
URL download method with the
command, CMake 3.23 and below sets the timestamps of the extracted contents
to the same as the timestamps in the archive. When the
URL changes, the
new archive is downloaded and extracted, but the timestamps of the extracted
contents might not be newer than the previous contents. Anything that depends
on the extracted contents might not be rebuilt, even though the contents may
CMake 3.24 and above prefers to set the timestamps of all extracted contents
to the time of the extraction. This ensures that anything that depends on the
extracted contents will be rebuilt whenever the
DOWNLOAD_EXTRACT_TIMESTAMP option to the
ExternalProject_Add() command can be used to explicitly specify how
timestamps should be handled. When
DOWNLOAD_EXTRACT_TIMESTAMP is not
given, this policy controls the default behavior. The
OLD behavior for
this policy is to restore the timestamps from the archive. The
behavior sets the timestamps of extracted contents to the time of extraction.
OLD behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.