If the 'sigmask' is NULL, the ppoll() is equivalent to poll()

with respect tio signal mask manipulations.

man2/poll.2

@@ -215,6 +215,18 @@ for an explanation of why
 .BR ppoll ()
 is necessary.
 
+If the
+.I sigmask
+argument is specified as NULL, then
+no signal mask manipulation is performed
+(and thus
+.BR ppoll ()
+differs from
+.BR poll ()
+only in the precision of the
+.I timeout
+argument).
+
 The
 .I timeout
 argument specifies an upper limit on the amount of time that