- wrenEnsureSlots()
Lets you go the foreign slot stack to make room for a temporary work
area.
- wrenSetSlotNewList()
Creates a new empty list and stores it in a slot.
- wrenInsertInList()
Takes a value from one slot and inserts it into the list in another.
Still need more functions like getting elements from a list, removing,
etc. but this at least lets you create, populate, and return lists from
foreign methods.
This turns those functions into general-purpose functions for writing
raw C values into slots on the foreign call stack.
Writing a return just means writing a value to slot 0.
- wrenGetArgumentCount() -> wrenGetSlotCount()
- wrenGetArgument___() -> wrenGetSlot___()
Also, the get functions assert that the value is the right type instead
of checking at runtime. This puts the onus on the caller to be safe,
but maximizes performance.
This is the first step towards dynamically grown stacks. We don't want
to check for stack overflow on every single push, so we store the max
number of slots a function might need and (in later patches) ensure
at function call time that that many slots are available.
If we ever support custom string templates, we'll need to go back to
compiling them to functions. But, for now, they can be evaluated
eagerly, leading to simpler code.
This allows "%(...)" inside a string literal to interpolate the
stringified result of an expression.
It doesn't support custom interpolators or format strings, but we can
consider extending that later.
- Make sure it handles an empty gray set.
- Make sure growing the gray stack doesn't itself trigger a GC.
- Make sure it works when stress testing is enabled.
- Ensure the tests kick off a GC.
The previous GC implementation used a recursive mark method. This can
result in stack overflows when attempting to mark deeply nested objects.
This commit replaces the recursive approach with an iteritive one,
moving the state stack from the C call stack to the `WrenVM` structure.
As objects are 'grayed' they are pushed onto the VM's gray stack. When
we have grayed all of the root objects we iterate until the stack is
empty graying any obejcts which haven't been marked as dark before. At
the end of the process we clean up all unmarked objects as before.
This commit also adds a few new tests which check garbage collection by
allocating some new deeply nested objects and triggering the GC a few
times in the process.
Wren now has three classes of modules:
- The one magic "core" module that's built in and always needed.
- Auxiliary libraries like "meta" and "random". These do not have any
dependencies, so can be used even when you embed Wren inside an
application. But they're also optional and can be disabled if you
don't need them.
- CLI modules. These ones need libuv and are tied to the CLI wrapper
around the VM.
Primitives still have a return value to indicate normal value returning
versus runtime errors or fiber switching since it minimizes branches
in the common case of a normal value result.
Instead, Fn.call(...) is a special *method* type that has the same
special sauce. The goal is eventually to get rid of the primitive
result type entirely.
- Add Fiber.transferError(_).
- Primitives place runtime errors directly in the fiber instead of on
the stack.
- Primitives that change fibers set it directly in the VM.
- Allow a fiber's error to be any object (except null).
- Add an explicit va_list version. That lets variadic functions
forward to it.
- Fix a GC bug in wrenCall() with return values.
- Make the call API test not re-enter the VM.
- Test that a foreign method can return strings.
- Test that a foreign method can return a string with null bytes.
- Test wrenCall().
- Allow passing NULL for "v" to wrenCall().
- Allow "a" for passing an explicit length byte array to wrenCall().
Get rid of the separate opt-in IO class and replace it with a core
System class.
- Remove wren_io.c, wren_io.h, and io.wren.
- Remove the flags that disable it.
- Remove the overloads for print() with different arity. (It was an
experiment, but I don't think it's that useful.)
- Remove IO.read(). That will reappear using libuv in the CLI at some
point.
- Remove IO.time. Doesn't seem to have been used.
- Update all of the tests, docs, etc.
I'm sorry for all the breakage this causes, but I think "System" is a
better name for this class (it makes it natural to add things like
"System.gc()") and frees up "IO" for referring to the CLI's IO module.
Bob Nystrom
Will Speak