With a recent change
g++ -DHAVE_CONFIG_H -I. -I.. -I/usr/include/freetype2
-I/usr/include/libpng16 -I/usr/include/freetype2 -I/usr/include/libpng16
-I/usr/include/qt5/QtCore -I/usr/include/qt5 -I/usr/include/qt5/QtGui
-I/usr/include/qt5/QtNetwork -I/usr/include/qt5/QtOpenGL
-I/usr/include/qt5/QtWidgets -I/usr/include/qt5/QtPrintSupport
-Ilibgui/graphics -I../libgui/graphics -Isrc -I../libgui/src
-I../liboctave/array -Iliboctave/numeric -I../liboctave/numeric
-Iliboctave/operators -I../liboctave/operators -I../liboctave/system
-I../liboctave/util -Ilibinterp -I../libinterp -Ilibinterp/parse-tree
-I../libinterp/parse-tree -Ilibinterp/corefcn -I../libinterp/corefcn
-I../libinterp/octave-value -fPIC -pthread -fopenmp -Wall -W -Wshadow
-Wold-style-cast -Wformat -Wpointer-arith -Wwrite-strings -Wcast-align
-Wcast-qual -g -O2 -MT
libgui/graphics/libgui_graphics_libgui_graphics_la-Figure.lo -MD -MP -MF
libgui/graphics/.deps/libgui_graphics_libgui_graphics_la-Figure.Tpo -c
../libgui/graphics/Figure.cc -fPIC -DPIC -o
libgui/graphics/.libs/libgui_graphics_libgui_graphics_la-Figure.o
../libgui/graphics/Figure.cc: In member function ‘void
QtHandles::Figure::fileSaveFigure(bool)’:
../libgui/graphics/Figure.cc:882:79: error: expected ‘)’ before ‘;’ token
QFileDialog::DontUseNativeDialog);
See also e.g.:
http://buildbot.octave.org:8010/builders/gcc-7-debian/builds/9/steps/compile/logs/stdio