https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66563
--- Comment #23 from John Paul Adrian Glaubitz <glaubitz at physik dot fu-berlin.de> --- It seems that Kaz was right. Downgrading libmpfr fixes the issue for me: glaubitz@tirpitz:~/debian/segfault-test/wmfire-1.2.4/src$ gcc wmfire.c -o wmfire.o $(pkg-config --cflags gdk-2.0) $(pkg-config --cflags libgtop-2.0) wmfire.c: In function ‘do_help’: wmfire.c:770:62: error: ‘VERSION’ undeclared (first use in this function) fprintf(stderr, "\nWmfire - Flaming Monitor Dock V %s\n\n", VERSION); ^ wmfire.c:770:62: note: each undeclared identifier is reported only once for each function it appears in glaubitz@tirpitz:~/debian/segfault-test/wmfire-1.2.4/src$ Adrian