Hi Nicolai,

please try and remember to invlude vm-dev when you see a VM issue...

On Sun, Aug 10, 2014 at 7:34 AM, Nicolai Hess <nicolaihess@web.de> wrote:

There is a certain risk, that the mustBeBooleanMagicIn method rewrite can crash the
vm
Issue 13805

Since you're using the Opal compiler ca you add the description of the bytecode (aCompiledMethod symbolic) to the issue? I'll try and take a look soon but want to be sure I'm debugging the relevant code.

The receiver of the rewritten method is the "nonboolean" value receiving the

ifTrue:ifFalse: message. But the rewritten method can include
instvar accessor and self sends of the original method.

We can include more rewrite rules in mustBeBooleanMagicIn like
"rewrite instvar accessing"

    context receiver class instVarNamesAndOffsetsDo: [ :n :o |
        RBParseTreeRewriter new
        replace: n with: ('ThisContext receiver instVarAt: ', o asString);
        executeTree: methodNode.
        ].
"rewrite self sends"
    RBParseTreeRewriter new
        replace: 'self' with: 'ThisContext receiver';
        executeTree: methodNode.

But I don't know if this works for all possible situations. Or if there are
better ways to do the rewriting.

Remember the mirror methods:

thisContext object: o instVarAt:

which doesn't send to o, reaching directly into it.

But what's the point of replacing "self" with "thisContext receiver"? The latter is potentially an extremely slow way of doing the former. The former won't create a context object in a method activation that doesn't need one (doesn't include a block), whereas the latter always will. But they will always yield the same result.

--
curious,

Eliot