Re: CVS commit: src/share/mk

[Taylor R Campbell <campbell+netbsd-source-changes-d%mumble.net@localhost>]

   Date: Thu, 23 Jan 2014 03:11:14 +0000
   From: Taylor R Campbell 
<campbell+netbsd-source-changes-d%mumble.net@localhost>

      Date: Wed, 22 Jan 2014 13:15:44 -0500
      From: christos%zoulas.com@localhost (Christos Zoulas)

      On Jan 22,  7:29am, matt%3am-software.com@localhost (Matt Thomas) wrote:
      -- Subject: Re: CVS commit: src/share/mk

      | I always wondered why we don't use ln -sf
      | and avoid the race.

      That does not work because if the destnation is a directory it will
      try to link in the destination directory... (I tried). This is why
      I suggested that it needs to be done differently.

   ln -sfh?

   As an aside, it would be nice if there were an easy way to create a
   symlink at a temporary location and rename it over the permanent one.
   `ln -sfh' will unlink instead, and mv(1) is too smart for its own good
   about directories to be able to rename over a symlink reliably...

Disregard me -- `ln -sfh' is just as bad as the other race precisely
because of the unlink/symlink sequence, and `-h' is not POSIX to boot.
If we do add a TOOL_LN, we ought to implement a symlink-to-temporary
rename-to-permanent operation so that it actually doesn't race.