js: fix runtime cleanup

This is a minefield.

Intuitively, you would think that just clearing the opaque and manually
freeing registered object should be enough. Unfortunately, this is
not true; we do not store whether we are actually holding a reference to
registered JS objects, so this approach leads to double frees.

Instead, we add a QJS callback that is called right after the final
GC cleanup, but before the list_free assertion. This way, we can be sure
that any object still in our registry is referenced by us, and can
therefore unreference them safely.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/bindings/quickjs.nim b/src/bindings/quickjs.nim
index 836bedac..20dd048b 100644
--- a/src/bindings/quickjs.nim
+++ b/src/bindings/quickjs.nim
@@ -132,6 +132,8 @@ type
   JSClassExoticMethodsConst* {.importc: "const JSClassExoticMethods *",
     header: qjsheader.} = ptr JSClassExoticMethods
 
+  JSRuntimeCleanUpFunc* {.importc.} = proc(rt: JSRuntime) {.cdecl.}
+
   JSClassDef* {.importc, header: qjsheader.} = object
     class_name*: cstring
     finalizer*: JSClassFinalizer
@@ -555,6 +557,8 @@ proc JS_ExecutePendingJob*(rt: JSRuntime; pctx: ptr JSContext): cint
 
 proc JS_GetRuntimeOpaque*(rt: JSRuntime): pointer
 proc JS_SetRuntimeOpaque*(rt: JSRuntime; p: pointer)
+proc JS_SetRuntimeCleanUpFunc*(rt: JSRuntime;
+  cleanup_func: JSRuntimeCleanUpFunc)
 
 proc JS_SetContextOpaque*(ctx: JSContext; opaque: pointer)
 proc JS_GetContextOpaque*(ctx: JSContext): pointer