Segault in ffglut with fill =0

General Discussion
1

This example seems to capture the problem and likely is reproducble.
Hitting return on the first plot causes a segfault as the attempt
to draw the “fill=0” fails,

    1 : mesh Th = square(100,100);
    2 : fespace Vh(Th,P1);
    3 : Vh xx=x;
    4 : plot(xx,fill=1,value=1,wait=1);
    5 : plot(xx,fill=0,value=1);

The first plot lets ma attach the debugger which then gives this stack trace,

Thread 1 "ffglut" received signal SIGSEGV, Segmentation fault.
0x00007f62ce86f505 in ?? () from /usr/lib/x86_64-linux-gnu/dri/iris_dri.so
(gdb) bt
#0  0x00007f62ce86f505 in ?? () from /usr/lib/x86_64-linux-gnu/dri/iris_dri.so
#1  0x00007f62ce89381e in ?? () from /usr/lib/x86_64-linux-gnu/dri/iris_dri.so
#2  0x00005630511afa90 in OnePlotFE<Fem2D::Mesh2>::Draw (this=0x7f62b415d990, 
    win=0x563052340240) at ./../femlib/RNM.hpp:417
#3  0x00005630511956bc in ThePlot::Draw (this=0x7f62b4000b60, 
    win=0x563052340240) at ../Graphics/ffglut.cpp:2585
#4  0x00005630511959ad in OneWindow::Display (this=0x563052340240)
    at ../Graphics/ffglut.cpp:2395
#5  OneWindow::Display (this=0x563052340240) at ../Graphics/ffglut.cpp:2379
#6  0x000056305119c66d in Display () at ../Graphics/ffglut.cpp:3748
#7  0x00007f62d0da1194 in ?? () from /usr/lib/x86_64-linux-gnu/libglut.so.3
#8  0x00007f62d0da4c39 in fgEnumWindows ()
   from /usr/lib/x86_64-linux-gnu/libglut.so.3
#9  0x00007f62d0da17bd in glutMainLoopEvent ()
   from /usr/lib/x86_64-linux-gnu/libglut.so.3
#10 0x00007f62d0da1ff5 in glutMainLoop ()
   from /usr/lib/x86_64-linux-gnu/libglut.so.3
#11 0x00005630511080ee in main (argc=<optimized out>, argv=<optimized out>)
    at ../Graphics/ffglut.cpp:4313
(gdb)

My freefem is linked as follows,

ldd `which FreeFem++`
	linux-vdso.so.1 (0x00007ffeb355a000)
	libumfpack.so.5 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libumfpack.so.5 (0x00007f7961599000)
	libcholmod.so.3 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libcholmod.so.3 (0x00007f7961490000)
	libarpack.so.2 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libarpack.so.2 (0x00007f7961443000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f7961421000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f79612d2000)
	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f79610ee000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f79610d3000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7960ee1000)
	libamd.so.2 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libamd.so.2 (0x00007f7960ed5000)
	libsuitesparseconfig.so.5 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libsuitesparseconfig.so.5 (0x00007f7960ed0000)
	libblas.so.3 => /usr/lib/x86_64-linux-gnu/libblas.so.3 (0x00007f7960e61000)
	libcolamd.so.2 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libcolamd.so.2 (0x00007f7960e57000)
	libccolamd.so.2 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libccolamd.so.2 (0x00007f7960e49000)
	libcamd.so.2 => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libcamd.so.2 (0x00007f7960e3b000)
	libmetis.so => /home/ubuntu/dev/freefem/install/ff-petsc/r/lib/libmetis.so (0x00007f7960dc9000)
	liblapack.so.3 => /usr/lib/x86_64-linux-gnu/liblapack.so.3 (0x00007f7960725000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f7960700000)
	libgfortran.so.5 => /usr/lib/x86_64-linux-gnu/libgfortran.so.5 (0x00007f7960438000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f7962714000)
	libquadmath.so.0 => /usr/lib/x86_64-linux-gnu/libquadmath.so.0 (0x00007f79603ee000)
2

probably more to the point, the libraries for ffglut.
I have not had time to look at it but someone else reported
this months ago and now I’ve got it
after upgrading to Focal from Beaver. It seems t be easy to produce
by setting fill=0.

ldd `which ffglut`
	linux-vdso.so.1 (0x00007ffd302b0000)
	libglut.so.3 => /usr/lib/x86_64-linux-gnu/libglut.so.3 (0x00007fdcbed4d000)
	libGLU.so.1 => /usr/lib/x86_64-linux-gnu/libGLU.so.1 (0x00007fdcbecdb000)
	libGL.so.1 => /usr/lib/x86_64-linux-gnu/libGL.so.1 (0x00007fdcbec53000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fdcbec30000)
	libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fdcbea4e000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fdcbe8fd000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fdcbe8e2000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fdcbe6f0000)
	libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007fdcbe5b3000)
	libXi.so.6 => /usr/lib/x86_64-linux-gnu/libXi.so.6 (0x00007fdcbe5a1000)
	libXxf86vm.so.1 => /usr/lib/x86_64-linux-gnu/libXxf86vm.so.1 (0x00007fdcbe59a000)
	libGLdispatch.so.0 => /usr/lib/x86_64-linux-gnu/libGLdispatch.so.0 (0x00007fdcbe4e0000)
	libGLX.so.0 => /usr/lib/x86_64-linux-gnu/libGLX.so.0 (0x00007fdcbe4ac000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fdcbf0a8000)
	libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007fdcbe482000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fdcbe47c000)
	libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007fdcbe467000)
	libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007fdcbe45f000)
	libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007fdcbe457000)
	libbsd.so.0 => /usr/lib/x86_64-linux-gnu/libbsd.so.0 (0x00007fdcbe43d000)
marchywka@happy:/home/documents/cpp/proj/freefem$