[CMake] Why CPack does not _ALWAYS_ use DESTDIR?

[Bill Hoffman]

Eric Noulard wrote:
> Hi All,
> 
> I did examine a problem with CPack RPM  generator which had
> been reported by a user:
> http://public.kitware.com/Bug/view.php?id=7000
> 
> The issue concerned file/target installed with absolute path name
> which leads to the following error:
> CMake Error at cmake_install.cmake:40 (FILE):
>   file cannot create directory: /absolute/path. Maybe need administrative
>   privileges.
> 
> /absolute/path being the absolute path used in a DESTINATION option
> of some INSTALL command.
> 
> This error can be fixed if we either:
> 
> SET(CPACK_SET_DESTDIR "ON") in the CMakeList.txt
> or
> force the same option from within the concerned CPack Generator code.
> 
> Afterwards I've tested all CPack generator enabled on my Linux box
> I did discover that ALL of them do encounter the same issue!!
> 
> My question is the following,
> 
> Why CPack does not _ALWAYS_ use DESTDIR?
> Why should the user
> SET(CPACK_SET_DESTDIR "ON") in the CMakeList.txt
> 
> I would really prefer to _ALWAYS_ set it ON i.e. get rid of it :=)
> 
> Does anybody knows why we sometimes DO NOT want to use DESTDIR
> for CPack generator?
> If there is no reason we may well enforce DESTDIR ON in the generic
> part of all CPack generator.
> 
Because for some projects DESTDIR may not work, and the default has been 
set.  To change it would break existing projects.

-Bill