Bug #9213
closedmkmf.rb emits invalid destination directory name for mswin32/64
Description
The install process of traditional extended library (=non gem) uses extconf.rb for creating Makefile and install the library by (n)make install.
However it does not work correctly because of FileUtil.mkdir met bad directory name as 'c:c:/...'.
This is caused by DESTDIR and prefix combination.
When one does not specify DESTDIR, rbconfig.rb create it as 'DESTDIR = TOPDIR && TOPDIR[/\A[a-z]:/i] || '' unless defined? DESTDIR' #=> 'C:' or 'D:'.
By the other hand CONFIG['prefix'] is (TOPDIR || DESTDIR + '/usr') so the prefixdir also contains 'c:' or 'd:' ...
The definition for install directories in mkmf.rb is defined as both DESTDIR and CONFIG['prefix'] directory for example '$(DESTDIR)$(vendorarchdir)$(target_prefix)'.
It causes the double drive letter name 'c:c:...'.
While there are some workarounds as using setup.rb or gem, it's harmful for the testing phase of extended libraries.