vm: add def for the segment struct, it's useful for testing

basis/vm/vm-tests.factor

@@ -0,0 +1,18 @@
+USING: accessors classes.struct kernel math math.order threads.private
+tools.test ;
+QUALIFIED: vm
+IN: vm.tests
+
+: get-ctx ( -- ctx )
+    context vm:context memory>struct ;
+
+{ t } [
+    get-ctx [ callstack-bottom>> ] [ callstack-top>> ] bi - 0 >
+] unit-test
+
+{ t } [
+    ! Callstack is in the callstack segment
+    get-ctx [ callstack-top>> ] [
+        callstack-seg>> [ start>> ] [ end>> ] bi
+    ] bi between?
+] unit-test

basis/vm/vm.factor

@@ -5,15 +5,20 @@ IN: vm
 
 TYPEDEF: uintptr_t cell_t
 
+STRUCT: segment
+    { start cell_t }
+    { size cell_t }
+    { end cell_t } ;
+
 STRUCT: context
-{ callstack-top void* }
-{ callstack-bottom void* }
+    { callstack-top cell_t }
+    { callstack-bottom cell_t }
     { datastack cell_t }
     { retainstack cell_t }
     { callstack-save cell_t }
-{ datastack-region void* }
-{ retainstack-region void* }
-{ callstack-region void* }
+    { datastack-seg segment* }
+    { retainstack-seg segment* }
+    { callstack-seg segment* }
     { context-objects cell_t[context-object-count] } ;
 
 : context-field-offset ( field -- offset ) context offset-of ; inline
@@ -32,7 +37,11 @@ STRUCT: vm
     { decks-offset cell_t }
     { signal-handler-addr cell_t }
     { faulting? cell_t }
-{ special-objects cell_t[special-object-count] } ;
+    { special-objects cell_t[special-object-count] }
+    { thread void* }
+    { datastack-size cell_t }
+    { retainstack-size cell_t }
+    { callstack-size cell_t } ;
 
 : vm-field-offset ( field -- offset ) vm offset-of ; inline