Re: [Help-smalltalk] reverse class order for instvar indexing

[Paolo Bonzini]

Stephen Compall wrote:
> I was getting instvar indexing conflicts (different classes would choose
> instvar 0 for different instvars) in Compiler until the attached tiny
> patch to STSymbolTable>>#declareEnvironment:.  Iterating from the other
> end of the inheritance tree seems to be what is intended by the readOnly
> calculation semantics, anyway.

Applied the patch, and reworked the readOnly stuff to be correct.  See 
the equivalent snippet of libgst/sym.c, where if the method is trusted 
all variables are read-write (in is_instance_variable_read_only).

@@ -157,18 +157,19 @@ addPool: poolDictionary

 declareEnvironment: aBehavior

-    | i readOnly |
+    | i canAlwaysStore inSandbox |
     environment := aBehavior.
+    inSandbox := thisContext isUntrusted.

     i := -1.
-    readOnly := aBehavior isUntrusted not and: [ thisContext isUntrusted ].
-    aBehavior withAllSuperclassesDo: [ :class |
-       readOnly := readOnly and: [ class isUntrusted not ].
+    canAlwaysStore := aBehavior isUntrusted.
+    aBehavior withAllSuperclasses reverseDo: [ :class |
+       canAlwaysStore := canAlwaysStore and: [ class isUntrusted ].
        class instVarNames do: [ :iv |
            instVars at: iv asSymbol put: (STVariable
                id: (i := i + 1)
                scope: 0
-               canStore: readOnly not).
+               canStore: (canAlwaysStore or: [ inSandbox not ])).
        ].
     ].
     self declareGlobals

Paolo