Building with gtk3 option in recent emacs git trunk, bootstrap was failure.
$ ./configure --with-x-toolkit=gtk3
$ make bootstrap
[...]
1.0/include -DORBIT2=1 -pthread -I/usr/include/gconf/2 -I/usr/include/orbit-2.0 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/freetype2 -MMD -MF deps/xterm.d -Wimplicit-function-declaration -Wold-style-definition -Wdeclaration-after-statement -Wno-pointer-sign -g -O2 xterm.c
xterm.c: In function 'x_set_frame_alpha':
xterm.c:449:3: warning: implicit declaration of function 'GDK_WINDOW_XWINDOW'
xterm.c: In function 'XTflash':
xterm.c:3027:5: error: 'GdkGCValues' undeclared (first use in this function)
xterm.c:3027:5: note: each undeclared identifier is reported only once for each function it appears in
xterm.c:3027:17: error: expected ';' before 'vals'
xterm.c:3028:5: error: 'GdkGC' undeclared (first use in this function)
xterm.c:3028:12: error: 'gc' undeclared (first use in this function)
xterm.c:3029:5: error: 'vals' undeclared (first use in this function)
xterm.c:3031:21: error: 'GDK_XOR' undeclared (first use in this function)
xterm.c:3032:5: warning: implicit declaration of function 'gdk_gc_new_with_values'
xterm.c:3033:41: error: 'GDK_GC_FUNCTION' undeclared (first use in this function)
xterm.c:3033:59: error: 'GDK_GC_FOREGROUND' undeclared (first use in this function)
xterm.c:3084:4: warning: implicit declaration of function 'gdk_draw_rectangle'
xterm.c: In function 'x_term_init':
xterm.c:9926:15: error: expected _expression_ before ')' token
make[2]: *** [xterm.o] Error 1
make[2]: Leaving directory `/home/sangu/git/emacs/src'
make[1]: *** [src] Error 2
make[1]: Leaving directory `/home/sangu/git/emacs'
make: *** [bootstrap] Error 2