Re: Cygwin make target is never determined up to date

[Dave Korn <dave dot korn dot cygwin at googlemail dot com>]

On 05/05/2010 06:04, Jeremy Bopp wrote:
> MichaelKim wrote:

>>          Prerequisite `../bin/build/chrome' is newer than
>>                  target `../bin/build/chrome/alt.jar'.
>>         Must remake target `../bin/build/chrome/alt.jar'.

> So let me get this straight.  The JAR file you're trying to build is
> within a directory which is listed as a prerequisite of that JAR file?
> Unless I'm completely off base, it would seem to be that this is
> expected behavior then.  If you mess with the contents of a directory,
> such as by adding a file to it, the last modified timestamp of the
> directory is going to be updated.  I would expect that to happen after
> the file is added to the directory which could very well be *after* the
> last modified timestamp of the file is set.  Thus the directory will
> appear newer than the file.

  Yep:

>     $(chrome_jar_file): $(jar_sources) $(jar_target_dir)

  The idea is supposed to be to make the jar file depend on the output dir, so
that if the output dir doesn't exist, the $(jar_target_dir) rule will get
invoked to mkdir it; but it doesn't anticipate that the timestamp of an
existing dir changes everytime you touch the files within it.

  For a discussion of better ways to create an output dir in make, see:

http://www.cmcrossroads.com/cm-articles/columns/ask-mr-make

The particular article you're looking for is #26, "Making directories in GNU
Make":

http://www.cmcrossroads.com/ask-mr-make/6936-making-directories-in-gnu-make

  I don't know why this would be working on the old XP machine, unless it's
running an older version of cygwin that had a bug or didn't implement updating
directory timestamps.

    cheers,
      DaveK


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