Store the line number of first use in implicitly declared variables as a numeric value, then synthesize a token at that line when reporting the error, ensuring bounded error message length even for pathologically long variable names.
Remove CODE_LOAD_MODULE and CODE_IMPORT_VARIABLE opcodes, replacing them with calls to System.importModule(_) and System.getModuleVariable(_,_) primitives. This simplifies the interpreter loop, improves performance by reducing bytecode dispatch, and prepares for moving module loading logic into Wren source code for embedder flexibility.
Remove the dedicated finalizer fiber from WrenVM and change finalizer functions to accept a void* data pointer instead of a full WrenVM reference. This prevents user code from interacting with the VM during garbage collection, simplifying the GC path and eliminating the need for pre-allocated fiber infrastructure. Update the WrenForeignClassMethods struct, all built-in finalizers (file, test), and the binding/calling logic accordingly.
Replace the internal `foreignStackStart` pointer with a public `apiStack` field
that tracks the base of available C API slots. Extract the static
`ensureStack` helper into a non-static `wrenEnsureStack` function declared in
the header, enabling `wrenEnsureSlots()` to create a fiber and stack when
called outside a foreign method. Update `callForeign` to use `apiStack` and
adjust `metaCompile` to write results through the new pointer. Add a
`ensureOutsideForeign` test that allocates slots on a fresh VM, verifies
slot count grows from 0 to 20, and exercises all 20 slots with double values
to confirm the stack is correctly initialized and usable.
The finalizer fiber is pre-allocated in the VM and reused for each finalizer call, replacing the previous approach that used a raw stack pointer. This ensures no memory allocation occurs during garbage collection when finalizers are invoked. The change also properly resets the fiber after each finalizer call and updates the GC rooting to include the new fiber.
The number of arguments can be derived from the stack pointer difference, eliminating the need to store it separately. Rename the slot pointer to better reflect its purpose as the start of the foreign call's stack region.
The previous implementation allowed fibers as map keys by assigning each fiber a unique numeric ID for hashing and equality. This was originally added to support a misguided attempt at thread-local storage that was never used. This commit removes the fiber ID field from ObjFiber, the nextFiberId counter from WrenVM, the fiber hashing case in hashObject(), and the IS_FIBER check in validateKey(). The error message for invalid keys is updated from "Key must be a value type or fiber." to "Key must be a value type." and all affected test expectations are updated accordingly.
Add `numSlots` and `maxSlots` fields to `Compiler` struct to track current and maximum stack usage during compilation. Introduce `stackEffects` array mapping each opcode to its net stack delta, defined via updated `OPCODE` macro in `wren_opcodes.h` now taking a second argument. Modify `initCompiler` to initialize slot tracking from `numLocals`, update `emitByte` and related emit functions to adjust `numSlots` and update `maxSlots` when a new peak is reached. Extend `ObjFn` with `maxSlots` field, pass it through `wrenNewFunction` calls (including `makeCallStub`), and fix a null-check in `wrenDumpCode` for core module name.
- Rename grayDepth to grayCount and maxGray to grayCapacity for clarity
- Fix gray stack growth condition to check capacity instead of depth
- Use config.reallocateFn directly instead of wrenReallocate wrapper
- Change blacken loop from do-while to while to handle empty gray set
- Remove separate initializeGC function and inline allocation in wrenNewVM
- Add explicit System.gc() calls in deeply_nested_gc and many_reallocations tests
- Normalize test output strings to lowercase "done"
Rename `wrenMarkValue` to `wrenGrayValue`, `wrenMarkBuffer` to `wrenGrayBuffer`, and `wrenDarkenObjs` to `wrenBlackenObjects` to make the tri-color garbage collection abstraction explicit. Introduce `wrenGrayObj` as a new helper that handles adding objects to the gray stack with cycle detection via the `isDark` flag. Update all call sites in the compiler, value, and VM modules to use the new names. Fix a typo in the VM header comment ("garbace" → "garbage").
The previous recursive `wrenMarkObj` approach could overflow the C stack when marking deeply nested object graphs. This commit introduces an iterative two-phase collector: objects are first "grayed" onto an explicit stack in the WrenVM struct, then `wrenDarkenObjs` iteratively processes the gray stack until all reachable objects are marked as "dark". The `marked` field is renamed to `isDark` to reflect the new semantics. A `gray` array with `grayDepth` and `maxGray` tracking is added to `WrenVM`, initialized in `initializeGC` and freed in `wrenFreeVM`. All internal mark calls (`markClass`, `markClosure`, `markFiber`, `wrenCollectGarbage`) are updated to use `wrenGrayObj` instead of `wrenMarkObj`. Two new test files (`deeply_nested_gc.wren` and `many_reallocations.wren`) verify that deeply nested object graphs and repeated GC cycles complete without stack overflow.
Add fallback empty UNREACHABLE() definition for GCC < 4.5 and non-MSVC compilers, and insert return/break statements after all UNREACHABLE() calls to prevent -Wreturn-type warnings when the macro expands to nothing. Also cast malloc result to char* in io.c to suppress C++ compilation warning.
The sourcePath field on ObjModule was redundant since it always matched the module name except for the main script. This change removes the parameter from wrenInterpret, wrenInterpretInModule, and wrenNewModule, and replaces all references to module->sourcePath with module->name in error reporting and debug output.
Add a `WrenWriteFn` callback to `WrenConfiguration` that allows host applications to control how text from `System.print()` and related functions is displayed. When set, the VM invokes this callback instead of directly calling `printf`. If the callback is NULL, printed text is silently discarded. The CLI's `initVM()` now registers a simple `write` function that prints to stdout, while the core `system_writeString` primitive checks for the callback before outputting. This change also refactors `wrenInitConfiguration` to set `defaultReallocate` as the default reallocation function and consolidates configuration fields into a single `WrenConfiguration` struct stored directly in `WrenVM`, removing separate member fields for reallocate, bindForeignMethod, bindForeignClass, loadModule, minNextGC, and heapScalePercent.
Add finalizer invocation for foreign objects during garbage collection by calling wrenFinalizeForeign in wrenFreeObj. Expose wrenCollectGarbage as a public API function and update internal calls accordingly. Ensure the "<finalize>" symbol is always registered in the symbol table even when no finalizer is provided. Add test fixtures for Resource class with finalizer and Api.gc/Api.finalized methods to verify finalization behavior across multiple GC cycles.
Implement the initial infrastructure for foreign classes in the Wren VM, including new opcodes (FOREIGN_CONSTRUCT, FOREIGN_CLASS), a WrenBindForeignClassFn callback type in the public API, and updated CLI vm.c to store and forward foreign binding callbacks via setForeignCallbacks(). The compiler now tracks whether a class is foreign via a new isForeign flag in ClassCompiler, emits CODE_FOREIGN_CONSTRUCT instead of CODE_CONSTRUCT for foreign class constructors, and errors on field definitions inside foreign classes. The debug dump and opcode header gain entries for the new opcodes, and wrenBindSuperclass handles the -1 numFields sentinel for foreign classes to prevent field inheritance from superclasses.
Introduce WrenValue type and wrenGetArgumentValue/wrenReleaseValue functions to allow C code to hold GC-safe references to Wren objects across foreign calls. Implement doubly-linked list management in VM struct, mark value handles during garbage collection, and add assertion in wrenFreeVM to detect unreleased values. Update test infrastructure with new get_value test case and rename existing test binding functions to camelCase convention.
Refactor wrenFindVariable to accept an explicit ObjModule* parameter instead of
implicitly using the main module. Promote the internal getCoreModule helper to
a public wrenGetCoreModule function declared in wren_vm.h. Update all call sites
in wren_core.c and wren_meta.c to pass the core module when looking up core
variables, and replace inline getCoreModule calls in wren_vm.c with the new
public function. Remove the NULL-module fallback documentation from
wrenDeclareVariable and wrenDefineVariable.
Add a unique numeric ID to each fiber allocation, enabling fibers to be used as map keys. This includes updating the hash function for OBJ_FIBER to return the fiber's ID, modifying key validation to accept fibers, updating documentation to describe the new capability, and adjusting all relevant test expectations and error messages.
Implement the `WrenBindForeignMethodFn` callback type and `bindForeignMethodFn` configuration field to allow host applications to resolve foreign method declarations at class definition time. Refactor the IO library to use this new binding mechanism instead of the previous `wrenDefineStaticMethod` approach, adding `foreign` keyword support to the lexer and compiler. Introduce `freeCompiler` helper for cleanup, store module names in `ObjModule`, and update the VM to call the binder when processing `CODE_METHOD_INSTANCE` and `CODE_METHOD_STATIC` opcodes for foreign methods.
Separate Wren VM library sources from CLI tool sources by moving them into
src/vm/ and src/cli/ subdirectories respectively. Update the Makefile to use
separate wildcard patterns for each directory, generate distinct object file
paths under build/vm/ and build/cli/, and adjust include paths to src/include.
Also update the Xcode project file to reference the new file locations.
