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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.10.2020 19:13, Anthony PERARD wrote:
> 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@xxxxxxxx>:
>>>>>
>>>>>> 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?

How's this different from an object file getting only partly written
and not deleted? We'd have to use the temporary file approach in
literally every rule if we wanted to cater for this.

Jan