io.backend.unix: init-signal-pipe function

Currently just reads off signal numbers and drops them.

basis/io/backend/unix/unix.factor

@@ -187,6 +187,13 @@ M: stdin cancel-operation
         size-read-fd <fd> init-fd <input-port> >>size
         data-read-fd <fd> >>data ;
 
+: signal-pipe-fd ( -- n )
+    OBJ-SIGNAL-PIPE special-object { fixnum } declare ; inline
+
+: init-signal-pipe ( -- )
+    signal-pipe-fd <fd> init-fd <input-port>
+    '[ [ 4 _ io:stream-read ] loop ] "Signals" spawn drop ;
+
 M: unix init-stdio
     <stdin> <input-port>
     1 <fd> <output-port>

core/kernel/kernel.factor

@@ -342,6 +342,8 @@ CONSTANT: OBJ-VM-COMPILER 72
 
 CONSTANT: OBJ-WAITING-CALLBACKS 73
 
+CONSTANT: OBJ-SIGNAL-PIPE 74
+
 ! Context object count and identifiers must be kept in sync with:
 !   vm/contexts.hpp