[apps] Apps are not allocated on the heap anymore but in a union hold by

the AppsContainerStorage

apps/Makefile

@@ -3,11 +3,11 @@ include apps/home/Makefile
 include apps/on_boarding/Makefile
 include apps/hardware_test/Makefile
 include apps/usb/Makefile
-snapshots =
+apps =
 
 # All selected apps are included. Each Makefile below is responsible for setting
-# the $snapshots variable (name of the snapshot class) and the $snapshot_headers
-# (path to the snapshot header).
+# the $apps variable (name of the app class) and the $app_headers
+# (path to the apps header).
 $(foreach i,${EPSILON_APPS},$(eval include apps/$(i)/Makefile))
 
 app_objs += $(addprefix apps/,\
@@ -33,14 +33,15 @@ app_objs += $(addprefix apps/,\
   variable_box_leaf_cell.o\
 )
 
-snapshots_declaration = $(foreach i,$(snapshots),$(i) m_snapshot$(subst :,,$(i));)
-snapshots_construction = $(foreach i,$(snapshots),,m_snapshot$(subst :,,$(i))())
-snapshots_list = $(foreach i,$(snapshots),,&m_snapshot$(subst :,,$(i)))
-snapshots_count = $(words $(snapshots))
-snapshot_includes = $(foreach i,$(snapshot_headers),-include $(i) )
+snapshots_declaration = $(foreach i,$(apps),$(i)::Snapshot m_snapshot$(subst :,,$(i))Snapshot;)
+apps_declaration = $(foreach i,$(apps),$(i) m_$(subst :,,$(i));)
+snapshots_construction = $(foreach i,$(apps),,m_snapshot$(subst :,,$(i))Snapshot())
+snapshots_list = $(foreach i,$(apps),,&m_snapshot$(subst :,,$(i))Snapshot)
+snapshots_count = $(words $(apps))
+snapshot_includes = $(foreach i,$(app_headers),-include $(i) )
 epsilon_app_names = '$(foreach i,${EPSILON_APPS},"$(i)", )'
 
-apps/apps_container_storage.o apps/main.o: CXXFLAGS += $(snapshot_includes) -DAPPS_CONTAINER_SNAPSHOT_DECLARATIONS="$(snapshots_declaration)" -DAPPS_CONTAINER_SNAPSHOT_CONSTRUCTORS="$(snapshots_construction)" -DAPPS_CONTAINER_SNAPSHOT_LIST="$(snapshots_list)" -DAPPS_CONTAINER_SNAPSHOT_COUNT=$(snapshots_count) -DEPSILON_APPS_NAMES=$(epsilon_app_names)
+apps/apps_container_storage.o apps/main.o: CXXFLAGS += $(snapshot_includes) -DAPPS_CONTAINER_APPS_DECLARATION="$(apps_declaration)" -DAPPS_CONTAINER_SNAPSHOT_DECLARATIONS="$(snapshots_declaration)" -DAPPS_CONTAINER_SNAPSHOT_CONSTRUCTORS="$(snapshots_construction)" -DAPPS_CONTAINER_SNAPSHOT_LIST="$(snapshots_list)" -DAPPS_CONTAINER_SNAPSHOT_COUNT=$(snapshots_count) -DEPSILON_APPS_NAMES=$(epsilon_app_names)
 
 
 i18n_files += $(addprefix apps/language_,$(addsuffix .universal.i18n, $(EPSILON_I18N)))

apps/apps_container_storage.h

@@ -13,7 +13,18 @@ public:
   AppsContainerStorage();
   int numberOfApps() override;
   App::Snapshot * appSnapshotAtIndex(int index) override;
+  void * currentAppBuffer() override { return &m_apps; };
 private:
+  union Apps {
+  public:
+    /* Enforce a trivial constructor and destructor that just leave the memory
+     * unmodified. This way, m_apps can be trivially destructed. */
+    Apps() {};
+    ~Apps() {};
+  private:
+    APPS_CONTAINER_APPS_DECLARATION
+  };
+  Apps m_apps;
   APPS_CONTAINER_SNAPSHOT_DECLARATIONS
 };
 

apps/calculation/Makefile

@@ -1,5 +1,5 @@
-snapshots += Calculation::App::Snapshot
-snapshot_headers += apps/calculation/app.h
+apps += Calculation::App
+app_headers += apps/calculation/app.h
 
 app_objs += $(addprefix apps/calculation/,\
   app.o\

apps/calculation/app.cpp

@@ -23,7 +23,7 @@ const Image * App::Descriptor::icon() {
 }
 
 App * App::Snapshot::unpack(Container * container) {
-  return new App(container, this);
+  return new (container->currentAppBuffer()) App(container, this);
 }
 
 void App::Snapshot::reset() {

apps/code/Makefile

@@ -1,5 +1,5 @@
-snapshots += Code::App::Snapshot
-snapshot_headers += apps/code/app.h
+apps += Code::App
+app_headers += apps/code/app.h
 
 app_objs += $(addprefix apps/code/,\
   app.o\

apps/code/app.cpp

@@ -27,7 +27,7 @@ App::Snapshot::Snapshot() :
 }
 
 App * App::Snapshot::unpack(Container * container) {
-  return new App(container, this);
+  return new (container->currentAppBuffer()) App(container, this);
 }
 
 void App::Snapshot::reset() {

apps/graph/Makefile

@@ -1,5 +1,5 @@
-snapshots += Graph::App::Snapshot
-snapshot_headers += apps/graph/app.h
+apps += Graph::App
+app_headers += apps/graph/app.h
 
 app_objs += $(addprefix apps/graph/,\
   app.o\

apps/probability/Makefile

@@ -1,5 +1,5 @@
-snapshots += Probability::App::Snapshot
-snapshot_headers += apps/probability/app.h
+apps += Probability::App
+app_headers += apps/probability/app.h
 
 app_objs += $(addprefix apps/probability/,\
   app.o\

apps/regression/Makefile

@@ -1,5 +1,5 @@
-snapshots += Regression::App::Snapshot
-snapshot_headers += apps/regression/app.h
+apps += Regression::App
+app_headers += apps/regression/app.h
 
 app_objs += $(addprefix apps/regression/,\
   app.o\

apps/sequence/Makefile

@@ -1,5 +1,5 @@
-snapshots += Sequence::App::Snapshot
-snapshot_headers += apps/sequence/app.h
+apps += Sequence::App
+app_headers += apps/sequence/app.h
 
 app_objs += $(addprefix apps/sequence/,\
   app.o\

apps/settings/Makefile

@@ -1,5 +1,5 @@
-snapshots += Settings::App::Snapshot
-snapshot_headers += apps/settings/app.h
+apps += Settings::App
+app_headers += apps/settings/app.h
 
 app_objs += $(addprefix apps/settings/,\
   app.o\

apps/solver/Makefile

@@ -1,5 +1,5 @@
-snapshots += Solver::App::Snapshot
-snapshot_headers += apps/solver/app.h
+apps += Solver::App
+app_headers += apps/solver/app.h
 
 app_objs += $(addprefix apps/solver/,\
   app.o\

apps/statistics/Makefile

@@ -1,5 +1,5 @@
-snapshots += Statistics::App::Snapshot
-snapshot_headers += apps/statistics/app.h
+apps += Statistics::App
+app_headers += apps/statistics/app.h
 
 app_objs += $(addprefix apps/statistics/,\
   app.o\

escher/include/escher/app.h

@@ -42,6 +42,8 @@ public:
     /* tidy clean all dynamically-allocated data */
     virtual void tidy();
   };
+  /* The destructor has to be virtual. Otherwise calling a destructor on an
+   * App * pointing to a Derived App would have undefined behaviour. */
   virtual ~App() = default;
   constexpr static uint8_t Magic = 0xA8;
   Snapshot * snapshot();

escher/include/escher/container.h

@@ -23,6 +23,7 @@ public:
   Container(Container&& other) = delete;
   Container& operator=(const Container& other) = delete;
   Container& operator=(Container&& other) = delete;
+  virtual void * currentAppBuffer() = 0;
   virtual void run();
   App * activeApp();
   virtual bool dispatchEvent(Ion::Events::Event event) override;

escher/src/app.cpp

@@ -18,7 +18,7 @@ const Image * App::Descriptor::icon() {
 
 void App::Snapshot::pack(App * app) {
   tidy();
-  delete app;
+  app->~App();
 }
 
 void App::Snapshot::reset() {