Re: [PATCH v2 2/5] Makefile: rename scripts in-place, don't clobber

> Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:
>
>> It'll also guard against any weird issues with e.g. a command that
>> wants to read GIT-PERL-DEFINES to generate one of the %.perl scripts
>> racing with either a concurrent instance of "make" that has partially
>> updated the file, or test-lib.sh dying with some particularly weird
>> error because GIT-BUILD-OPTIONS was partway through being updated when
>> it ran.
>
> If something like that happens, doesn't that indicate a bug in the
> dependency graph in the Makefile or the implementation of "make"?
> The generated file is depended on for the consumer to be able to use
> a non-stale version---so the consumer should not start before the
> generator finishes.

> You may be able to hide the breakage coming from "partially written
> file is easily recognizable and the consumer would barf".  But I am
> afraid that you are introducing a problem harder to diagnose, i.e.
> "the consumer reads from a complete file so there is no syntax error
> or other things that easily tells you there is a breakage, but what
> is used is stale and not up to date".
>
> The same comment applies to this step.  I do not think it would
> break (other than adding intermediate crufts) the result if you
> generate into temporary and rename to final, but it is not clear
> to me what the point is in doing so.