Bug in R8B-1 (and -0) using set_port_control_flags() in driver?

Scott Lystig Fritchie <>
Sun Apr 14 22:23:49 CEST 2002


Please pardon me for this abbreviated bug (?) report and lack of fix.

On a lark, I tried adding a call to set_port_control_flags(port,
PORT_CONTROL_FLAG_BINARY) in my test driver's "start" function.
Without the set_port_control_flags() call in "start", I get a list of
3 bytes.  With the call to set_port_control_flags(), I get a bogus
binary of random size instead.

       Erlang (BEAM) emulator version 5.1.1 [source] [threads:5]
       
       Eshell V5.1.1  (abort with ^G)
       1> P1 = foodrv:open().
       #Port<0.29>
       2> X = foodrv:do_control(P1, 2,0).
       <<64,7,29,8,0,0,0,0,72,0,0,0,24,180,55,8,200,239,191,191,20,180,55,8,212,239,191,191,213,...>>
       3> size(X).
       3214020608
       4> q().
       ok
       
FWIW, here's what do_control() looks like:

do_control(Port, Sec, MSec) ->
    case erlang:port_control(Port, ?AS_CMD_ASLEEP, <<Sec:32, MSec:32>>) of
	<<0:8, Tag:16>> ->			% FIXME Const for OK status
	    receive
		{Port, Tag, M} -> M
	    end;
	XXX ->
	    XXX
    end.

If I leave out the set_port_control_flags() and use this instead, it
works fine.

do_control(Port, Sec, MSec) ->
    case erlang:port_control(Port, ?AS_CMD_ASLEEP, <<Sec:32, MSec:32>>) of
	[0, Tag1, Tag2] ->			% FIXME Const for OK status
	    Tag = (Tag1 bsl 8) bor Tag2,
	    receive
		{Port, Tag, M} -> M
	    end;
	XXX ->
	    XXX
    end.

I'll just avoid using set_port_control_flags() for now.

-Scott



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