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

(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 https://salsa.debian.org/postgresql/postgresql-common/blob/master/pg_buildext#L53-55

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

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/Makefile.global.in b/src/Makefile.global.in
index 956fd274cd..42bdf9f75c 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -674,8 +674,14 @@ ifdef COPT
LDFLAGS += $(COPT)
endif

+ifdef CXXOPT
+ CXXFLAGS += $(CXXOPT)
+ LDFLAGS += $(CXXOPT)
+endif
+
ifdef PROFILE
CFLAGS += $(PROFILE)
+ CXXFLAGS += $(PROFILE)
LDFLAGS += $(PROFILE)
endif

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

Christoph
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