Add STANDARDS and HISTORY to getcontext(3), makecontext(3), and ucontext(3).

Obtained from:	NetBSD
MFC after:	2 weeks
Sponsored by:	DARPA

lib/libc/gen/getcontext.3

@@ -35,7 +35,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 13, 2013
+.Dd March 23, 2020
 .Dt GETCONTEXT 3
 .Os
 .Sh NAME
@@ -148,3 +148,35 @@ No memory was available to allocate for the context or some extended state.
 .Xr sigaltstack 2 ,
 .Xr makecontext 3 ,
 .Xr ucontext 3
+.Sh STANDARDS
+The
+.Fn getcontext
+and
+.Fn setcontext
+functions conform to
+.St -xsh5
+and
+.St -p1003.1-2001 .
+The
+.Va errno
+indications are an extension to the standard.
+.Pp
+The
+.St -p1003.1-2004
+revision marked the functions
+.Fn getcontext
+and
+.Fn setcontext
+as obsolete, citing portability issues and recommending the use of
+.Tn POSIX
+threads instead.
+The
+.St -p1003.1-2008
+revision removed the functions from the specification.
+.Sh HISTORY
+The
+.Fn getcontext
+and
+.Fn setcontext
+functions first appeared in
+.At V.4 .

lib/libc/gen/makecontext.3

@@ -35,7 +35,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 31, 2018
+.Dd March 23, 2020
 .Dt MAKECONTEXT 3
 .Os
 .Sh NAME
@@ -123,3 +123,41 @@ to complete the operation.
 .Sh SEE ALSO
 .Xr setcontext 3 ,
 .Xr ucontext 3
+.Sh STANDARDS
+The
+.Fn makecontext
+and
+.Fn swapcontext
+functions conform to
+.St -xsh5
+and
+.St -p1003.1-2001 .
+.Pp
+The
+.St -p1003.1-2004
+revision marked the functions
+.Fn makecontext
+and
+.Fn swapcontext
+as obsolete, citing portability issues and recommending the use of
+.Tn POSIX
+threads instead.
+The
+.St -p1003.1-2008
+revision removed the functions from the specification.
+.Pp
+.Bf -symbolic
+The standard does not clearly define the type of integer arguments
+passed to
+.Fa func
+via
+.Fn makecontext ;
+portable applications should not rely on the implementation detail that
+it may be possible to pass pointer arguments to functions.
+.Sh HISTORY
+The
+.Fn makecontext
+and
+.Fn swapcontext
+functions first appeared in
+.At V.4 .

lib/libc/gen/ucontext.3

@@ -35,7 +35,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 10, 2002
+.Dd March 23, 2020
 .Dt UCONTEXT 3
 .Os
 .Sh NAME
@@ -109,3 +109,15 @@ structures:
 .Xr getcontext 3 ,
 .Xr getcontextx 3 ,
 .Xr makecontext 3
+.Sh STANDARDS
+The
+.Vt ucontext_t
+type conforms to
+.St -xsh5
+and
+.St -p1003.1-2001 .
+The
+.St -p1003.1-2008
+revision removed the
+.Vt ucontext_t
+from the specification.