Index: generic/nsf.c
===================================================================
diff -u -N -rfebe765f7fac1308029fd203b89e974e3ded8ee4 -r8f7c25f980c5433948a27be3cab5bb15d754b921
--- generic/nsf.c	(.../nsf.c)	(revision febe765f7fac1308029fd203b89e974e3ded8ee4)
+++ generic/nsf.c	(.../nsf.c)	(revision 8f7c25f980c5433948a27be3cab5bb15d754b921)
@@ -10973,7 +10973,7 @@
   if (newItem != 0) {
     Tcl_SetHashValue(hPtr, INT2PTR(1));
   } else {
-    int count = PTR2INT(Tcl_GetHashValue(hPtr));
+    long count = PTR2INT(Tcl_GetHashValue(hPtr));
     Tcl_SetHashValue(hPtr, INT2PTR(count+1));
   }
 }
@@ -13866,7 +13866,7 @@
 
   if (ttPtr != NULL) {
     const char      *methodName = data[0];
-    unsigned int     cmdFlags   = PTR2UINT(data[3]);
+    unsigned int     cmdFlags   = (unsigned int)PTR2UINT(data[3]);
 #if defined(NSF_PROFILE)
     NsfRuntimeState *rst        = RUNTIME_STATE(interp);
 #endif
@@ -23380,7 +23380,8 @@
     const char *errorMsg =  ObjStr(resultObj);
 
     INCR_REF_COUNT(resultObj);
-    fprintf(stderr, "==== DEBUG AppVeyor: calling NsfForwardPrintError with <<%s>> (len %lu)\n", errorMsg, strlen(errorMsg));
+    fprintf(stderr, "==== DEBUG AppVeyor: calling NsfForwardPrintError with <<%s>> (len %lu)\n",
+            errorMsg, (unsigned long)strlen(errorMsg));
     result = NsfForwardPrintError(interp, tcd, objc, objv, "%s", errorMsg);
     DECR_REF_COUNT(resultObj);
   }
Index: generic/nsfAccessInt.h
===================================================================
diff -u -N -ra963e8896fd07c345ccfa034cbd043344edbf083 -r8f7c25f980c5433948a27be3cab5bb15d754b921
--- generic/nsfAccessInt.h	(.../nsfAccessInt.h)	(revision a963e8896fd07c345ccfa034cbd043344edbf083)
+++ generic/nsfAccessInt.h	(.../nsfAccessInt.h)	(revision 8f7c25f980c5433948a27be3cab5bb15d754b921)
@@ -81,6 +81,14 @@
 #define Tcl_Command_deleteProc(cmd)    ((Command *)(cmd))->deleteProc
 #define Tcl_Command_deleteData(cmd)    ((Command *)(cmd))->deleteData
 
+/* 
+ * The offsetof() macro is an ANSI C library feature.
+ * Workaround for platforms missing offsetof(), e.g. VC++ 6.0 
+ */
+#ifndef offsetof
+# define offsetof(type, field) ((size_t) ((char *) &((type *) 0)->field))
+#endif
+
 /*
  * Var Reform Compatibility support.
  *
@@ -91,7 +99,7 @@
 #define TclIsCompiledLocalArgument(compiledLocalPtr)  ((compiledLocalPtr)->flags & VAR_ARGUMENT)
 #define TclIsCompiledLocalTemporary(compiledLocalPtr) ((compiledLocalPtr)->flags & VAR_TEMPORARY)
 
-#define TclVarHashGetValue(hPtr)	((Var *) ((char *)(hPtr) - TclOffset(VarInHash, entry)))
+#define TclVarHashGetValue(hPtr)	((Var *) ((char *)(hPtr) - offsetof(VarInHash, entry)))
 #define TclVarHashGetKey(varPtr)	(((VarInHash *)(varPtr))->entry.key.objPtr)
 #define TclVarHashTablePtr(varTablePtr)		&(varTablePtr)->table
 #define TclVarValue(type, varPtr, field)	(type *)(varPtr)->value.field