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fix: Root HTML rewriter variables to ensure no GC #1202

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Merged
merged 1 commit into from
Sep 29, 2025
Merged

fix: Root HTML rewriter variables to ensure no GC #1202

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15 changes: 13 additions & 2 deletions runtime/fastly/builtins/html-rewriter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -353,7 +353,10 @@ bool HTMLRewritingStream::onElement(JSContext *cx, unsigned argc, JS::Value *vp)

struct OutputContextData {
JSContext *cx;
JSObject *self;
JS::Heap<JSObject *> self;
bool enqueue_failed;

OutputContextData(JSContext *cx, JSObject *self) : cx(cx), self(self), enqueue_failed(false) {}
};

void HTMLRewritingStream::finalize(JS::GCContext *gcx, JSObject *self) {
Expand Down Expand Up @@ -387,7 +390,7 @@ void HTMLRewritingStream::finalize(JS::GCContext *gcx, JSObject *self) {
static void output_callback(const char *chunk, size_t chunk_len, void *user_data) {
auto *ctx = static_cast<OutputContextData *>(user_data);
JSContext *cx = ctx->cx;
JSObject *self = ctx->self;
JS::RootedObject self(cx, ctx->self);

JS::RootedObject out_obj(cx, JS_NewUint8Array(cx, chunk_len));
if (!out_obj) {
Expand All @@ -405,6 +408,7 @@ static void output_callback(const char *chunk, size_t chunk_len, void *user_data
JS::RootedValue out_chunk(cx, JS::ObjectValue(*out_obj));

if (!TransformStreamDefaultController::Enqueue(cx, controller, out_chunk)) {
ctx->enqueue_failed = true;
return;
}
}
Expand Down Expand Up @@ -468,6 +472,13 @@ bool HTMLRewritingStream::transformAlgorithm(JSContext *cx, unsigned argc, JS::V
return false;
}

auto output_context = static_cast<OutputContextData *>(
JS::GetReservedSlot(self, HTMLRewritingStream::Slots::OutputContext).toPrivate());
if (output_context->enqueue_failed) {
JS_ReportErrorASCII(cx, "Error processing HTML: output stream enqueue failed");
return false;
}

args.rval().setUndefined();
return true;
}
Expand Down
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