Build & make check fine on OpenBSD (6.0-current). The test `threads-io-switch' fails when runs in graphical emacs (gtk3). Here is the backtrace (no debug symbol) : #0 0x000000000054739a in SPECPDL_INDEX () #1 0x00000000005126c2 in handle_one_xevent () #2 0x0000000000514ffe in x_dispatch_event () #3 0x00000000005123fe in event_handler_gdk () #4 0x0000000284df0ca0 in gdk_event_apply_filters () from /usr/local/lib/libgdk-3.so.2200.2 #5 0x0000000284df0e00 in _gdk_x11_display_queue_events () from /usr/local/lib/libgdk-3.so.2200.2 #6 0x0000000284db98e8 in gdk_display_get_event () from /usr/local/lib/libgdk-3.so.2200.2 #7 0x0000000284df0b06 in gdk_event_source_dispatch () from /usr/local/lib/libgdk-3.so.2200.2 #8 0x000000021077965f in g_main_context_dispatch () from /usr/local/lib/libglib-2.0.so.4200.4 #9 0x000000000069c458 in xg_select () #10 0x00000000006754db in really_call_select () #11 0x00000000005ce3c3 in flush_stack_call_func () #12 0x0000000000675570 in thread_select () #13 0x000000000064e4c1 in wait_reading_process_output () #14 0x000000000064ca59 in Faccept_process_output () #15 0x00000000005f449f in eval_sub () #16 0x00000000005f07b9 in Fprogn () #17 0x00000000005f1a7a in Fwhile () #18 0x00000000005f4002 in eval_sub () #19 0x00000000005f07b9 in Fprogn () #20 0x00000000005f4002 in eval_sub () #21 0x00000000005f090e in Fsetq () #22 0x00000000005f4002 in eval_sub () #23 0x00000000005f1f02 in Funwind_protect () #24 0x00000000005f4002 in eval_sub () #25 0x00000000005f068f in Fif () #26 0x00000000005f4002 in eval_sub () #27 0x00000000005f07b9 in Fprogn () #28 0x00000000005f19b2 in Flet () #29 0x00000000005f4002 in eval_sub () #30 0x00000000005f07b9 in Fprogn () #31 0x00000000005f19b2 in Flet () #32 0x00000000005f4002 in eval_sub () #33 0x00000000005f07b9 in Fprogn () #34 0x00000000005f6828 in funcall_lambda () #35 0x00000000005f5b95 in Ffuncall () #36 0x000000000063fbfe in exec_byte_code () #37 0x00000000005f652f in funcall_lambda () #38 0x00000000005f5adf in Ffuncall () I didn't look further yet. Thanks for your work!