When sage uses pkgconfig to determine compile flags, for example in src/module_list.py and src/sage/env.py it only extracts the "libraries" but not the "libs" field from pkg-config. In the case of fflas-ffpack this field (as well as cflags) contains -fopenmp. So sage builds but does not link with this flag which leads to missing symbols on Ubuntu:

ImportError: /<<PKGBUILDDIR>>/debian/build/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_sparse.so: undefined symbol: GOMP_loop_ull_runtime_start

This was mentioned in https://bugs.debian.org/919573 .

To reproduce:

  tox -e docker-debian-bullseye-standard

The resulting sage crashes on startup with the above error.

Applying the Debian patch reveals another Sage bug:

$ pkg-config --libs linbox
-L/sage/local/lib -llinbox @LINBOXSAGE_LIBS@ -lntl -lmpfr -liml -lflint -fopenmp -lblas -llapack -lgivaro -lgmp -lgmpxx

This is linbox upstream issue linbox-team/linbox#170

This ticket fixes both.

CC: @kiwifb @ClementPernet @antonio-rojas @dimpase @mkoeppe @isuruf @vbraun

Component: build

Author: Tobias Hansen, Matthias Koeppe

Branch: d678f78

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/27205