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Date: Mon, 23 Nov 2009 03:39:51 +0000
From: Dave Korn <dave DOT korn DOT cygwin AT googlemail DOT com>
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Subject: Re: Problem with autoconf autodepend
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Ken Brown wrote:

> I guess so.  I wonder if there's a timing problem so that the deps
> directory isn't being created before it needs to be used.  But here's
> something very strange:  Angelo Graziosi, who is also playing with this,
> told me that he *doesn't* get error if he does 'make -j4', but he gets
> the same error I get with just plain 'make'.  I would expect the
> opposite if it were a timing problem.

  No, that (potentially) makes perfect sense to me.  There's a bug in the
makefile; it either has no or wrong dependency for the deps subdir, so it
doesn't get created until later in the dependency order than it is first
actually needed.  If you run at -j4, some of the things later in the
dependency order get to happen earlier, including perhaps creating the deps
directory, but if you run it in serial dependency order at -j1 the deps dir
isn't created in time before it's first used.

  Can't say for sure whether or not that is what's actually happening, but
it's quite plausible.

> I'm also confused about what the configure test is supposed to be doing
> (see my original post).  I can't see that it creates the deps directory,
> so I don't understand why it succeeds.

  Because it doesn't try to output the dependency file into a subdir at all:

>      CFLAGS="$CFLAGS -MMD -MF deps.d"

it just outputs it straight into the current dir, alongside the conftest.c
test compile, so it doesn't fail.

    cheers,
      DaveK

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