CMP0135ΒΆ
New in version 3.24.
When using the URL
download method with the ExternalProject_Add()
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
change.
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 URL
changes.
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 NEW
behavior sets the timestamps of extracted contents to the time of extraction.
This policy was introduced in CMake version 3.24. CMake version 3.25.3
warns when the policy is not set and uses OLD
behavior. Use the
cmake_policy()
command to set it to OLD
or NEW
explicitly.
Note
The OLD
behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.