Re: Reproducible builds: genbki.pl and Gen_fmgrtab.pl

On 12/20/2017 09:50 PM, Tom Lane wrote:
> Christoph Berg <christoph(dot)berg(at)credativ(dot)de> writes:
>> Re: Tom Lane 2017-12-16 <417(dot)1513438031(at)sss(dot)pgh(dot)pa(dot)us>
>>> I think we're talking at cross-purposes. I'm not saying we should not fix
>>> this problem. I'm saying that the proposed fix appears incomplete ...
>> Grepping through the source, there are three places where $0 printed
>> to files in regular operation (as opposed to being used in --help):
> I poked around and found a few more.
>
>> I believe the reason why we've only been seeing half of the problem
>> yet is that the generated files are shipped with the tarballs, so it
>> might be a timestamping issue determining if the scripts are
>> re-executed.
> Right; some parts of this problem would only materialize for you if you
> needed to rebuild the generated files that are included in the tarball,
> which should basically not be happening in normal packager builds.
> Rather the risk is at our end: if we ever switched the tarball creation
> process to be a VPATH build, then there'd be path dependencies in the
> created tarballs. That would be bad.
>
> More generally, my concern here is not just that we fix this problem
> but that it stays fixed. If some individual scripts print $0 into
> their output and it happens to not affect any built distribution files
> today, it's still bad, because tomorrow somebody might copy that coding
> pattern into someplace else where it matters more. I think we need a
> project policy that thou shalt not print $0 into generated files, period.
>
> Also, experimenting with a VPATH build, I verified that such "helpful"
> practices as printing $infile or @ARGV into the output file will also
> create path dependencies. So I think we need to lose those too.
> It's not like they're adding any info you can't find out from the
> Makefiles.
>
> On the other hand, there is something we can do that will improve
> matters: rather than just printing the base name of the script,
> let's print its full relative path within the PG sources, eg instead
> of Gen_fmgrtab.pl let's print src/backend/utils/Gen_fmgrtab.pl.
> My thought here is that if you're not already intimately familiar
> with a script you might not remember where it lives, the more so
> if you're looking at a file that's been put into an installation
> tree far away from where it was generated. I see that this policy
> was already followed in some places, just not in the ones that were
> using the $0 shortcut.
>
> In short, I propose the attached more-extensive patch.
>
> Some of the files generated by these scripts, particularly the map
> files generated by the src/backend/utils/mb/Unicode/ scripts, are
> not just present in tarballs but are actually in our git repo.
> So changing those scripts won't affect anything until/unless someone
> updates the repo's generated files, which I've not done here and
> don't feel much need to do. I just want to establish a principle
> that we don't print path-dependent info into generated files.
>
>

Looks reasonable. Regarding the change to TestLib.pm, we should make
sure that the tests have unique names. There is a small amount of
duplication currently:

./src/bin/pg_dump/t/001_basic.pl
./src/bin/pg_rewind/t/001_basic.pl
./src/test/modules/commit_ts/t/001_base.pl
./src/test/modules/test_pg_dump/t/001_base.pl

cheers

andrew

--

Andrew Dunstan https://www.2ndQuadrant.com
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