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Re: recursive make [Was: Help-make Digest, Vol 77, Issue 5]

From: Paul Smith
Subject: Re: recursive make [Was: Help-make Digest, Vol 77, Issue 5]
Date: Sat, 11 Apr 2009 22:00:53 -0400

On Sat, 2009-04-11 at 17:42 -0400, Michael R. Head wrote:
> The idea is to declare that a given subdirectory is dependent on just
> the files contained within it. Thus, the recursive make call should only
> be rebuilt when those dependencies are newer than the directory. I'm
> probably missing something glaringly obvious, though... 

I don't see how this can work reliably, at least not on any POSIX-like

Timestamps on directories are updated when, and only when, the directory
is modified; that is, a new file is added, or a file is removed, or a
file is renamed.  Modifying an existing file doesn't change the
timestamp on the directory, for example.

That means that if a new file was added (depending on how your editor
works), or a "make clean" was done, or similar, then the directory
timestamp will be newer than any file in the directory... and yet the
build is completely out of date.

 Paul D. Smith <address@hidden>          Find some GNU make tips at:            
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist

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