The VM used to not detect this case. It meant you could get into a
situation where another fiber's caller had completed. Then, when it
tried to resume that fiber, the VM would crash because there was nothing
to resume to.
This is part of thinking through all the cases around re-entrancy. Added
some notes for that too.
There's a lot of changes here and surely some rough edges to iron out.
Also, I need to update the docs. But I want to get closer to landing
this so I can build on it.
- Fix some doc comments.
- Inline comparing two ObjStrings, since it's only used in one place.
Also, this avoids a redundant identity check.
- Move the forward declarations of the object types out of
wren_common.h. Instead, I just added the one needed forward
declaration of ObjString in wren_utils.h. It's a little inelegant,
but it feels weird to me to expose all of the object types in
wren_common.h when they logically belong to wren_value.h and most of
the types aren't problematic.
- Fix a bug where field symbol tables weren't being marked. If a GC
happened while compiling a class, field strings got freed.
A statement like:
for (i in 1..2)
When run in the REPL declares a local variable ("i"), but not inside
a function or method body. This hit a corner case in the compiler
where it didn't have the correct slot indexes set up.
That corner case is because sometimes when you compile a chunk, local
slot zero is pre-allocated -- either to refer to "this" or to hold the
closure for a function so that it doesn't get GCed while running. But
if you're compiling top-level code, that slot isn't allocated. But top
level code for the REPL *should* be, because that gets invoked like a
function.
To simplify things, *every* compiled chunk now pre-allocates slot zero.
That way, there are fewer cases to keep in mind.
Also fixed an issue where a GC during an import could collected the
imported module body's closure.
Fix#456.
