From 2fa181645c32d6fafeaef2c9a4a508286d9c4e1a Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Sat, 12 Sep 2026 04:12:16 +0000
Subject: [PATCH] fix(devtools): avoid pause-on-caught-throw for raw VM DAP
 attach
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

DevTool::attach(HSQUIRRELVM) enabled sq_notifyallexceptions, so with
break-on-error the error hook paused at the throw site before catch /
reportError ran. That left a second pause hanging after one DAP continue
and flaked as SEGFAULT on Linux CI teardown
(devtools.dap.caughtErrorPausesAtReportSite). Keep notify-all only on
Runtime-bound attach (hook already capture-only there) and force-resume
in the test if the script thread is still paused.

Co-authored-by: 西风逍遥游 <sunxfancy@gmail.com>
---
 src/engine/devtools/DevTool.cpp | 10 +++++++++-
 test/dap.cpp                    |  7 +++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/engine/devtools/DevTool.cpp b/src/engine/devtools/DevTool.cpp
index f41add73..8b9f0448 100644
--- a/src/engine/devtools/DevTool.cpp
+++ b/src/engine/devtools/DevTool.cpp
@@ -135,6 +135,10 @@ void DevTool::attach(ssq::VM& vm, bool sampleLocals) { attach(vm.getHandle(), sa
 void DevTool::attach(eve::Runtime& runtime, bool sampleLocals) {
     attach(runtime.vm(), sampleLocals);
     runtime_ = &runtime;
+    // Capture throw-site stacks for try/catch so reportError / lastScriptError
+    // can surface the original site (load.nut pattern). Safe here because the
+    // Runtime-bound error hook only stashes context and does not notify/pause.
+    sq_notifyallexceptions(runtime.handle(), SQTrue);
     // Route Runtime-boundary errors into the slicer/report. The VM error hook
     // only captures the stack when this Runtime sink is bound; this handler
     // reports compile / reflect / unload failures and uncaught execute errors
@@ -182,7 +186,11 @@ void DevTool::attach(HSQUIRRELVM vm, bool sampleLocals) {
     Debugger::instance().setPump([this]() { pumpWhilePaused(); });
 
     sq_enabledebuginfo(vm_, SQTrue);
-    sq_notifyallexceptions(vm_, SQTrue);
+    // Do not enable sq_notifyallexceptions here. With notify-all + break-on-error,
+    // this hook would pause on every caught throw before script catch/reportError
+    // runs (double pause → hung script thread → flaky teardown SEGFAULT in
+    // devtools.dap.caughtErrorPausesAtReportSite). Runtime::installErrorHandler
+    // already turns notify-all on for production VMs; attach(Runtime&) keeps it.
     sq_setnativedebughook(vm_, nativeDebugHook);
     // Route uncaught script errors into the debugger (break-on-error aware).
     sq_newclosure(vm_, runtimeErrorHook, 0);
diff --git a/test/dap.cpp b/test/dap.cpp
index a86db9c3..55ea8ee5 100644
--- a/test/dap.cpp
+++ b/test/dap.cpp
@@ -869,6 +869,13 @@ TEST_CASE("devtools.dap.caughtErrorPausesAtReportSite") {
         std::this_thread::sleep_for(std::chrono::milliseconds(10));
         dap.poll();
     }
+    // If the script thread is still blocked in waitWhilePaused, force-resume
+    // before teardown so dap.stop()/detach cannot race a paused VM (SEGFAULT).
+    if (!scriptDone.load() && dbg.isPaused()) dbg.resume();
+    for (int i = 0; i < 100 && !scriptDone.load(); ++i) {
+        std::this_thread::sleep_for(std::chrono::milliseconds(10));
+        dap.poll();
+    }
     if (scriptThread.joinable()) {
         if (scriptDone.load())
             scriptThread.join();