Re: [PATCH] Pass COPT and PROFILE to CXXFLAGS as well

From: Christoph Berg <christoph(dot)berg(at)credativ(dot)de>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Pass COPT and PROFILE to CXXFLAGS as well
Date: 2018-11-21 13:28:01
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(Sorry for the delayed response here.)

Re: Andres Freund 2018-11-13 <20181113223330(dot)2ql7tg33hhh6husf(at)alap3(dot)anarazel(dot)de>
> > >> While working on making extension modules built reproducibly, I
> > >> noticed that extra flags passed via COPT (notably -ffile-prefix-map)
> > >> do not get added to CXXFLAGS.
> >
> > > PROFILE I can see, but COPT I'm less sure. The name suggests it's about
> > > C not C++. How about adding CXXOPT?

Any of that would work, I was adding it to both because both were the
same so far.

> > > Secondary question: Why aren't you using CFLAGS/CXXFLAGS for this?

The context here is that we want to use the *FLAGS from pg_config for
compiling PG extension packages, but add additional *FLAGS from the
extension build environment. Merging the pg_config CFLAGS with the
environment CFLAGS seemed hard/weird/error-prone, so what we are doing
now is

if [ "${CFLAGS:-}" ]; then
export COPT="$CFLAGS"

Which works nicely.

> > COPT (and PROFILE) are handy for injecting additional flags manually;
> > they're even documented for that (cf installation.sgml, around line
> > 1550).
> > I agree that CXXOPT would be a better idea than COPT for this.
> Yea, I agree that we want CXX equivalent of the feature, especially for
> -Werror. I'm just not sure that's the best fit for the debian build
> issue Christoph ran into. I guess the goal is to *not* include the
> -ffile-prefix-map in the CFLAGS for extensions, unless those are also
> built via debian machinery?

-ffile-prefix-map (or actually still -fdebug-prefix-map, -ffile-p-m is
WIP) is the reason for the extra flags, yes. We can't use pg_config's
version here because the build path for PG is not the build path for
the extension module.

> > Not sure about PROFILE. But we could inject the latter into both
> > flag sets and then document that if that's not what you want, use
> > COPT.
> That seems reasonable to me too.

Updated patch:

diff --git a/src/ b/src/
index 956fd274cd..42bdf9f75c 100644
--- a/src/
+++ b/src/
@@ -674,8 +674,14 @@ ifdef COPT

+ifdef CXXOPT

I didn't patch the documentation yet because I wasn't sure if the
LDFLAGS handling with CXXOPT makes sense.

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