Re: [PATCH v1] libacpi: use temporary files for generated files

[Anthony PERARD <anthony.perard@citrix.com>]

On Tue, Oct 27, 2020 at 12:06:56PM +0100, Jan Beulich wrote:
> On 27.10.2020 11:57, Andrew Cooper wrote:
> > On 27/10/2020 10:37, Jan Beulich wrote:
> >> On 27.10.2020 11:27, Olaf Hering wrote:
> >>> Am Tue, 27 Oct 2020 11:16:04 +0100
> >>> schrieb Jan Beulich <jbeulich@suse.com>:
> >>>
> >>>> This pattern is used when a rule consists of multiple commands
> >>>> having their output appended to one another's.
> >>> My understanding is: a rule is satisfied as soon as the file exists.
> >> No - once make has found that a rule's commands need running, it'll
> >> run the full set and only check again afterwards.
> > 
> > It stops at the first command which fails.
> > 
> > Olaf is correct, but the problem here is an incremental build issue, not
> > a parallel build issue.
> > 
> > Intermediate files must not use the name of the target, or a failure and
> > re-build will use the (bogus) intermediate state rather than rebuilding it.
> 
> But there's no intermediate file here - the file gets created in one
> go. Furthermore doesn't make delete the target file(s) when a rule
> fails? (One may not want to rely on this, and hence indeed keep multi-
> part rules update intermediate files of different names.)

What if something went badly enough and sed didn't managed to write the
whole file and make never had a chance to remove the bogus file?

Surely, this patch is a strict improvement to the build system.

Cheers,

-- 
Anthony PERARD