common/async: Don't get allocator from moved-from handler

In the `destroy_` functions of `CompletionImpl` we were getting the
associated allocator after moving out of the handler into the call to
`bind_and_forward`. This was triggering a crash on null-pointer access
in operations made with `co_composed`.

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>

diff --git a/src/common/async/completion.h b/src/common/async/completion.h
index 384c85f0fe380657568e4cc482c23510e55dd960..a7dd7370f02496e1d7c511b75b871037f13b0339 100644 (file)
--- a/src/common/async/completion.h
+++ b/src/common/async/completion.h
@@ -189,24 +189,24 @@ class CompletionImpl final : public Completion<void(Args...), T> {
 
   void destroy_defer(std::tuple<Args...>&& args) override {
     auto w = std::move(work);
-    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindAlloc2 alloc2 = boost::asio::get_associated_allocator(handler);
+    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindTraits2::destroy(alloc2, this);
     RebindTraits2::deallocate(alloc2, this, 1);
     w.second.get_executor().defer(std::move(f), alloc2);
   }
   void destroy_dispatch(std::tuple<Args...>&& args) override {
     auto w = std::move(work);
-    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindAlloc2 alloc2 = boost::asio::get_associated_allocator(handler);
+    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindTraits2::destroy(alloc2, this);
     RebindTraits2::deallocate(alloc2, this, 1);
     w.second.get_executor().dispatch(std::move(f), alloc2);
   }
   void destroy_post(std::tuple<Args...>&& args) override {
     auto w = std::move(work);
-    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindAlloc2 alloc2 = boost::asio::get_associated_allocator(handler);
+    auto f = bind_and_forward(std::move(handler), std::move(args));
     RebindTraits2::destroy(alloc2, this);
     RebindTraits2::deallocate(alloc2, this, 1);
     w.second.get_executor().post(std::move(f), alloc2);