The previous formula `vm->bytesAllocated * (100 + heapGrowthPercent) / 100` incorrectly computed the total heap size instead of the additional allocation threshold, causing the GC to trigger endlessly when `bytesAllocated` already exceeded the calculated `nextGC` value. The fix changes the calculation to `bytesAllocated + (bytesAllocated * heapGrowthPercent / 100)`, which properly represents the next collection point as the current allocation plus a growth allowance. This resolves the infinite GC loop observed in `test/language/deeply_nested_gc.wren` on 32-bit architectures.
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.
Append a new contributor entry for Will Speak with their email address
to the project's AUTHORS file, following the existing formatting
convention used for other contributors.
Extend the compiler's string parser to handle `\U` escapes with 8 hex digits
for codepoints above U+FFFF, replacing the previous TODO comment. The
`readUnicodeEscape` helper now accepts a variable digit count (4 or 8) and
the `readString` function dispatches `\u` with length 4 and `\U` with length 8.
New test cases verify correct encoding of emoji and ancient scripts, plus
error handling for incomplete long escapes and values that fit in 4 digits.
Will Speak