diff --git a/basis/ForeignConstants.580.sml b/basis/ForeignConstants.580.sml
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+++ b/basis/ForeignConstants.580.sml
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+(*
+    Title:      Foreign Function Interface: constants
+    Author:     David Matthews
+    Copyright   David Matthews 2015, 2016-17
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License version 2.1 as published by the Free Software Foundation.
+    
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+    
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*)
+
+(* This is defined separately so that the values are computed and
+   available as constants for the Foreign structure. *)
+structure ForeignConstants =
+struct
+    local
+        val ffiGeneralCall = RunCall.rtsCallFull2 "PolyFFIGeneral"
+        fun ffiGeneral(code: int, arg: 'a): 'b = RunCall.unsafeCast(ffiGeneralCall(RunCall.unsafeCast(code, arg)))
+    in
+    local
+        fun getSizeAndAlign (n: int) =
+        let
+            val ffiType = ffiGeneral (52, n)
+            val (size: word, align: word, _, _) = (* Just get the first two fields. *)
+                ffiGeneral (53, ffiType)
+        in
+            {size=size, align=align}
+        end
+    in
+        val saVoid      = getSizeAndAlign 0
+        and saUint8     = getSizeAndAlign 1
+        and saSint8     = getSizeAndAlign 2
+        and saUint16    = getSizeAndAlign 3
+        and saSint16    = getSizeAndAlign 4
+        and saUint32    = getSizeAndAlign 5
+        and saSint32    = getSizeAndAlign 6
+        and saUint64    = getSizeAndAlign 7
+        and saSint64    = getSizeAndAlign 8
+        and saFloat     = getSizeAndAlign 9
+        and saDouble    = getSizeAndAlign 10
+        and saPointer   = getSizeAndAlign 11
+        and saUChar     = getSizeAndAlign 12
+        and saSChar     = getSizeAndAlign 13
+        and saUShort    = getSizeAndAlign 14
+        and saSShort    = getSizeAndAlign 15
+        and saUint      = getSizeAndAlign 16
+        and saSint      = getSizeAndAlign 17
+        and saUlong     = getSizeAndAlign 18
+        and saSlong     = getSizeAndAlign 19
+    end
+    
+    val bigEndian : bool = LibrarySupport.bigEndian
+    and wordSize : word = RunCall.bytesPerWord
+    and sysWordSize: word = LibrarySupport.sysWordSize
+    
+    (* Minimum argument size. *)
+    val ffiMinArgSize: Word.word = ffiGeneral (51, 15)
+    end
+
+end;