Re: [RFC] building postgres with meson - perl embedding

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-hackers(at)postgresql(dot)org, Peter Eisentraut <peter(at)eisentraut(dot)org>
Subject: Re: [RFC] building postgres with meson - perl embedding
Date: 2022-02-08 01:42:09
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Andres Freund <andres(at)anarazel(dot)de> writes:
> What is the reason behind subtracting ccdlflags?

It looks like the coding actually originated here:

commit f5d0c6cad5bb2706e0e63f3f8f32e431ea428100
Author: Bruce Momjian <bruce(at)momjian(dot)us>
Date: Wed Jun 20 00:26:06 2001 +0000

Apparently, on some systems, ExtUtils::Embed and MakeMaker are slightly
broken, and its impossible to make a shared library when compiling with
both CCDLFLAGS and LDDLFAGS, you have to pick one or the other.

Alex Pilosov

and Peter just copied the logic in 7662419f1. Considering that
the point of 7662419f1 was to get rid of MakeMaker, maybe we no
longer needed that at that point.

On my RHEL box, the output of ldopts is sufficiently redundant
that the subtraction doesn't actually accomplish much:

$ perl -MExtUtils::Embed -e ldopts
-Wl,--enable-new-dtags -Wl,-z,relro -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -Wl,-z,relro -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -fstack-protector-strong -L/usr/local/lib -L/usr/lib64/perl5/CORE -lperl -lpthread -lresolv -ldl -lm -lcrypt -lutil -lc

$ perl -MConfig -e 'print $Config{ccdlflags}'
-Wl,--enable-new-dtags -Wl,-z,relro -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld

which leads to

$ grep perl_embed_ldflags src/
perl_embed_ldflags = -Wl,-z,relro -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -fstack-protector-strong -L/usr/local/lib -L/usr/lib64/perl5/CORE -lperl -lpthread -lresolv -ldl -lm -lcrypt -lutil -lc

so the only thing we actually got rid of was -Wl,--enable-new-dtags,
which I think we'll put back anyway.

Things might be different elsewhere of course, but I'm tempted
to take out the ccdlflags subtraction and see what the buildfarm

regards, tom lane

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