CPack/Deb: Remove paxr as a supported tar format for a .deb

The only format supported from the ones available within cpack is
gnutar, which supports large numbers encoded in base-256, and long
filenames and linknames. PAX is not and has never been a supported
format by dpkg.

Fixes: #18620

Help/cpack_gen/deb.rst

@@ -205,18 +205,18 @@ List of CPack DEB generator specific variables:
  The archive format used for creating the Debian package.
 
  * Mandatory : YES
- * Default   : "paxr"
+ * Default   : "gnutar"
 
- Possible values are:
+ Possible value is:
 
- - paxr
  - gnutar
 
  .. note::
 
-   Default pax archive format is the most portable format and generates
-   packages that do not treat sparse files specially.
-   GNU tar format on the other hand supports longer filenames.
+   This variable previously defaulted to the ``paxr`` value, but ``dpkg``
+   has never supported that tar format. For backwards compatibility the
+   ``paxr`` value will be mapped to ``gnutar`` and a deprecation message
+   will be emitted.
 
 .. variable:: CPACK_DEBIAN_COMPRESSION_TYPE
 

Help/release/dev/cpack-deb-tar-format.rst

@@ -0,0 +1,7 @@
+cpack-deb-tar-format
+--------------------
+
+* The :module:`CPack` module no longer defaults to the ``paxr`` value in the
+  :variable:`CPACK_DEBIAN_ARCHIVE_TYPE` variable, because ``dpkg`` has
+  never supported the PAX tar format. The ``paxr`` value will be mapped
+  to ``gnutar`` and a deprecation message emitted.

Modules/Internal/CPack/CPackDeb.cmake

@@ -482,13 +482,16 @@ function(cpack_deb_prepare_package_vars)
   endif()
 
   if(CPACK_DEBIAN_ARCHIVE_TYPE)
-    set(archive_types_ "paxr;gnutar")
-    if(NOT CPACK_DEBIAN_ARCHIVE_TYPE IN_LIST archive_types_)
+    if(CPACK_DEBIAN_ARCHIVE_TYPE STREQUAL "paxr")
+      message(DEPRECATION "CPACK_DEBIAN_ARCHIVE_TYPE set to old and invalid "
+        "type 'paxr', mapping to 'gnutar'")
+      set(CPACK_DEBIAN_ARCHIVE_TYPE "gnutar")
+    elseif(NOT CPACK_DEBIAN_ARCHIVE_TYPE STREQUAL "gnutar")
       message(FATAL_ERROR "CPACK_DEBIAN_ARCHIVE_TYPE set to unsupported"
         "type ${CPACK_DEBIAN_ARCHIVE_TYPE}")
     endif()
   else()
-    set(CPACK_DEBIAN_ARCHIVE_TYPE "paxr")
+    set(CPACK_DEBIAN_ARCHIVE_TYPE "gnutar")
   endif()
 
   # Compression: (recommended)

Source/CPack/cmCPackDebGenerator.cxx

@@ -80,7 +80,7 @@ DebGenerator::DebGenerator(
   , WorkDir(workDir)
   , TopLevelDir(topLevelDir)
   , TemporaryDir(temporaryDir)
-  , DebianArchiveType(debianArchiveType ? debianArchiveType : "paxr")
+  , DebianArchiveType(debianArchiveType ? debianArchiveType : "gnutar")
   , ControlValues(controlValues)
   , GenShLibs(genShLibs)
   , ShLibsFilename(shLibsFilename)