Added asan and ubsan to CI

.github/workflows/build_matrix.yml

@@ -33,6 +33,14 @@ jobs:
             cxx: "g++",
             generators: "Ninja"
           }
+        - {
+            name: "ubuntu g++ asan+ubsan",
+            os: ubuntu-latest,
+            build_type: "Debug",
+            cxx: "g++",
+            generators: "Ninja",
+            cxx_flags: "-fsanitize=address,undefined -fno-sanitize-recover=all -fno-omit-frame-pointer -g"
+          }
         - {
             name: "macos clang++",
             os: macos-latest,
@@ -80,6 +88,7 @@ jobs:
             -B . \
             -DCMAKE_BUILD_TYPE=${{ matrix.config.build_type }} \
             -DCMAKE_CXX_COMPILER=${{ matrix.config.cxx }} \
+            -DCMAKE_CXX_FLAGS="${{ matrix.config.cxx_flags }}" \
             -DSML_BUILD_EXAMPLES=ON \
             -DSML_BUILD_TESTS=ON \
             -G "${{ matrix.config.generators }}"

include/boost/sml.hpp

@@ -2309,7 +2309,10 @@ struct sm_impl : aux::conditional_t<aux::should_not_subclass_statemachine_class<
       // transitions and defer drains between queued events (#542).
       typename process_t::value_type event{static_cast<typename process_t::value_type &&>(process_.front())};
       process_.pop();  // pop before dispatch so re-entrant calls see an advanced queue (#465)
-      queued_handled &= (this->*dispatch_table[event.id])(d, subs, event.data);
+      // Subscript in its own statement to dodge a GCC(-O0) ASan+UBSan miscompilation/crash on
+      // the folded (this->*dispatch_table[event.id])(...) call.
+      const auto handler = dispatch_table[event.id];
+      queued_handled &= (this->*handler)(d, subs, event.data);
     }
     return wasnt_empty;
   }