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Re: possible race condition in makefile with multiple dependencies?

  • Subject: Re: possible race condition in makefile with multiple dependencies?
  • From: "Robert P. J. Day" <rpjday [ at ] crashcourse [ dot ] ca>
  • Date: Thu, 3 Jun 2021 10:27:33 -0400 (EDT)
On Thu, 3 Jun 2021, Dianne Skoll wrote:

> On Thu, 3 Jun 2021 10:19:22 -0400
> "Michael P. Soulier" <msoulier [ at ] digitaltorque [ dot ] ca> wrote:
>
> > On 2021-06-03 10:09 a.m., Dianne Skoll wrote:
> > > See the -j option
>
> > Seems like a race condition waiting to happen.
>
> Shouldn't be.  My understanding (which may be wrong) is that make
> calculates the dependency graph first, not in parallel.  Then it
> executes as many parallel tasks as the -j option asks for, or that
> make sense... whichever is smaller.  Since the dependency graph is a
> DAG, make should, in theory, be smart enough to see that two
> dependencies depend on the same node and run only one job to build
> the depended-upon node.
>
> I routinely use "make -j `nproc`" and have never run into any
> issues.

  this was my understanding as well, i just wanted to hear some
confirmation from someone else.

rday

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