sage-env exports empty CXXFLAGS

[nexttime]

That happens if CFLAGS are empty (or not exported at all, which presumably is the most frequent case) and CXXFLAGS aren't either:

if [ "$CXXFLAGS" = "" ]; then
    export CXXFLAGS="$CFLAGS"
fi

Unintentionally having exported but empty CXXFLAGS breaks at least MPIR, because it assumes the user had intentionally set them, so leaves them as they are (empty that is), not passing potentially important architecture and ABI flags to the C++ compiler (e.g. -m... flags to g++).

The solution is of course simple: Don't (set and) export CXXFLAGS if CFLAGS aren't exported either. Not sure if setting CXXFLAGS to CFLAGS in case the latter are non-empty (or empty but exported) is desirable at all.

CC: @jpflori

Component: scripts

Keywords: CFLAGS MPIR C++ ABI

Author: Frédéric Chapoton

Branch/Commit: 420fa5f

Reviewer: Volker Braun

Issue created by migration from https://trac.sagemath.org/ticket/16149

[nexttime]

comment:1

I'd suggest to replace the above with at least

if [ "${CFLAGS+set}" = set ] && [ -z "$CXXFLAGS" ]; then
    export CXXFLAGS="$CFLAGS"
fi

which only sets (and exports) CXXFLAGS in case CFLAGS are set (but probably to "") and CXXFLAGS are empty.

Or only use CFLAGS if they're really non-empty by adding && [ -n "$CFLAGS" ] or replacing [ "${CFLAGS+set}" = set ] by the former.

[nexttime]

comment:2

It would probably make sense to even unset both in case they're just empty. (Same for FCFLAGS and CPPFLAGS etc.)

[nexttime]

comment:3

Typo.

[fchapoton]

Branch: u/chapoton/16149

[fchapoton]

New commits:

5c9bce6

trac #16149 proposal

[fchapoton]

Commit: 5c9bce6

[fchapoton]

Author: Frédéric Chapoton

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

420fa5f

trac #16149 typos

[sagetrac-git]

Changed commit from 5c9bce6 to 420fa5f

[vbraun]

Reviewer: Volker Braun

[vbraun]

Changed branch from u/chapoton/16149 to 420fa5f