From 99c1534dfa089ff740214205d2099ce82a5404c8 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Mon, 5 Jul 2021 08:29:01 -0700
Subject: [PATCH] client: add ConnectBuilder::syncCancel()

---
 src/client.cpp    | 12 ++++++------
 src/pvxs/client.h | 10 ++++++++++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/client.cpp b/src/client.cpp
index a5bc0c4..8e3cedb 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -204,26 +204,26 @@ std::shared_ptr<Connect> ConnectBuilder::exec()
     if(!ctx)
         throw std::logic_error("NULL Builder");
 
+    auto syncCancel(_syncCancel);
     auto context(ctx->impl->shared_from_this());
 
     auto op(std::make_shared<ConnectImpl>(context->tcp_loop, _pvname));
     op->_onConn = std::move(_onConn);
     op->_onDis = std::move(_onDis);
 
-    std::shared_ptr<ConnectImpl> external(op.get(), [op](ConnectImpl*) mutable {
+    std::shared_ptr<ConnectImpl> external(op.get(), [op, syncCancel](ConnectImpl*) mutable {
         // from user thread
-        auto loop(op->loop);
+        auto temp(std::move(op));
+        auto loop(temp->loop);
         // std::bind for lack of c++14 generalized capture
         // to move internal ref to worker for dtor
-        loop.call(std::bind([](std::shared_ptr<ConnectImpl>& op) {
+        loop.tryInvoke(syncCancel, std::bind([](std::shared_ptr<ConnectImpl>& op) {
                       // on worker
 
                       // ordering of dispatch()/call() ensures creation before destruction
                       assert(op->chan);
                       op->chan->connectors.remove(op.get());
-                  }, std::move(op)));
-        assert(!op);
-        op.reset();
+                  }, std::move(temp)));
     });
 
     context->tcp_loop.dispatch([op, context]() {
diff --git a/src/pvxs/client.h b/src/pvxs/client.h
index f29a254..024fef1 100644
--- a/src/pvxs/client.h
+++ b/src/pvxs/client.h
@@ -829,6 +829,7 @@ class ConnectBuilder
     std::string _pvname;
     std::function<void()> _onConn;
     std::function<void()> _onDis;
+    bool _syncCancel = true;
 public:
     ConnectBuilder(const std::shared_ptr<Context::Pvt>& ctx, const std::string& pvname)
         :ctx(ctx)
@@ -840,6 +841,15 @@ public:
     //! Handler to be invoked when channel becomes disconnected.
     ConnectBuilder& onDisconnect(std::function<void()>&& cb) { _onDis = std::move(cb); return *this; }
 
+    /** Controls whether Connect::~Connect() synchronizes.
+     *
+     * When true (the default) explicit or implicit cancel blocks until any
+     * in progress callback has completed.  This makes safe some use of
+     * references in callbacks.
+     * @since UNRELEASED
+     */
+    ConnectBuilder& syncCancel(bool b) { this->_syncCancel = b; return *this; }
+
     //! Submit request to connect
     PVXS_API
     std::shared_ptr<Connect> exec();