[PATCH] gas: rework timestamp preservation on doc/asconfig.texi

[Jan Beulich]

On 31.07.2023 16:29, Nick Clifton wrote:
>> PR 28909
>>
>> Sadly "cp -p", doing more than just preserving the time stamp, can fail
>> e.g. upon trying to preserve ownership (which we don't care about), as
>> can be observed on e.g. Cygwin. Replace the use of -p by a use of touch,
>> this way also only preserving modification time.
> 
> Thanks for fixing this.  If you have not done so already, please also apply
> the patch to the 2.41 branch.

I will; I haven't pushed to master either, to first see if there are
comments (or if perhaps we want to undo the earlier change).

>> Interestingly that earlier commit (8034b0baeac1) looks to also be the
>> reason of there now being "GEN    doc/asconfig.texi" on every
>> (incremental) rebuild.
> 
> Strange, I thought that the point was to avoid this kind of thing.
> 
>> Would be nice if that could be avoided. 
> 
> Rebuilding does not take that long though, does it ?

No, it's quick. But the expectation from an incremental build is that
only files depending on ones which were touched would be rebuilt. Hence
me noticing that slight anomaly.

>> How
>> important is it to actually retain the timestamp? Said commit said
>> nothing on the "Why" aspect ... The issue described in the bug doesn't
>> look like it wants dealing with by using "cp -p" (or alike).
> 
> Well as I understood it, the point was that using "cp -p" meant that the
> timestamps on the doc/asconfig.tex and doc/asconfig.texi files would
> always be the same, so the build system would not decide to rebuild the
> documentation and hence there would be no problem if the makeinfo program
> was not available.

First of all I was under the impression that there are already
precautions for that case. But I may be wrong (in which cases it may be
worth trying to introduce such logic), or such logic may have bit-rotted.
(On Cygwin I have been using MAKEINFO=true on the make command line
virtually forever, to escape such issues. Until things broke earlier
today, when I tried building 2.41.) And then my experience with build
systems tells me that it is extremely rare that fiddling with time stamps
is an appropriate solution. But then I'm afraid I may not properly
understand the original issue, and hence this might be a case where doing
so is justified.

Jan