Upgrade: switch to C++23 (see #1245)

The Lumiera »Reference Platform« is now upgraded to Debian/Buster, which provides GCC-14 and Clang-20.
Thus the compiler support for C++20 language features seems solid enough, and C++23,
while still in ''experimental stage'' can be seen as a complement and addendum.

This changeset
 * upgrades the compile switches for the build system
 * provides all the necessary adjustments to keep the code base compilable

Notable changes:
 * λ-capture by value now requires explicit qualification how to handle `this`
 * comparison operators are now handled transparently by the core language,
   largely obsoleting boost::operators. This change incurs several changes
   to implicit handling rules and causes lots of ambiguities — which typically
   pinpoint some long standing design issues, especially related to MObjects
   and the ''time entities''. Most tweaks done here can be ''considered preliminary''
 * unfortunately the upgraded standard ''fails'' to handle **tuple-like** entities
   in a satisfactory way — rather an ''exposition-only'' concept is introduced,
   which applies solely to some containers from the STL, thereby breaking some
   very crucial code in the render entities, which was built upon the notion of
   ''tuple-like'' entities and the ''tuple protocol''. The solution is to
   abandon the STL in this respect and **provide an alternative implementation**
   of the `apply` function and related elements.

admin/scons/Setup.py

@@ -65,7 +65,7 @@ def defineBuildEnvironment():
     env.Replace( CPPPATH   =["#src"]    # used to find includes, "#" means always absolute to build-root
                , CPPDEFINES=['LUMIERA_VERSION='+VERSION ]    # note: it's a list to append further defines
                , CCFLAGS='-Wall -Wextra -Wformat-security'
-               , CXXFLAGS='-std=gnu++17 -Wno-enum-compare'
+               , CXXFLAGS='-std=gnu++23 -Wno-enum-compare'
                , CFLAGS='-std=gnu99'
                )
     env.Append(LINKFLAGS='-Wl,--no-undefined')  # require every dependency is given on link, in the right order

src/common/guifacade.cpp

@@ -115,7 +115,7 @@ namespace stage {
             
             facade.reset (   //  trigger loading of the GuiStarterPlugin...
               new GuiRunner (
-                    [=] (string* problemMessage)
+                    [=,this] (string* problemMessage)
                         { //     will be invoked when the UI thread exits
                           closeGuiModule();
                           termNotification(problemMessage);

src/lib/allocation-cluster.hpp

@@ -121,8 +121,8 @@ namespace lib {
      ~AllocationCluster ()  noexcept;
       
       /** hard wired size of storage extents */
-      static size_t constexpr EXTENT_SIZ = 256;
+      static constexpr size_t EXTENT_SIZ = 256;
-      static size_t constexpr max_size();
+      static constexpr size_t max_size();
       
       
       /* === diagnostics === */

src/lib/depend-inject.hpp

@@ -293,13 +293,13 @@ namespace lib {
           
           template<class FUN>
           explicit
-          Local (FUN&& buildInstance)
+          Local (FUN&& _buildInstance)
             {
               __assert_compatible<MOC>();
               __assert_compatible<typename SubclassFactoryType<FUN>::Subclass>();
               
               temporarilyInstallAlternateFactory (origInstance_, origFactory_
-                                                 ,[=]()
+                                                 ,[this, buildInstance=forward<FUN> (_buildInstance)]
                                                     {
                                                       mock_.reset (buildInstance());
                                                       return mock_.get();

src/lib/meta/tuple-closure.hpp

@@ -44,6 +44,7 @@
 #define LIB_META_TUPLE_CLOSURE_H
 
 #include "lib/meta/function-closure.hpp"
+#include "lib/meta/tuple-helper.hpp"
 #include "lib/util.hpp"
 
 #include <utility>
@@ -140,7 +141,7 @@ namespace meta{
                     auto
                     operator() (RemainingParams remPar)  const
                       {
-                        return std::apply (unConst(this)->partialClosure_, remPar);
+                        return apply (unConst(this)->partialClosure_, remPar);
                       };
 
                     CLO partialClosure_;

src/lib/meta/tuple-helper.hpp

@@ -42,6 +42,7 @@
 
 #include <tuple>
 #include <utility>
+#include <functional>
 
 
 namespace util { // forward declaration
@@ -78,6 +79,56 @@ namespace meta {
   using disable_if_Tuple = lib::meta::disable_if<lib::meta::is_Tuple<std::remove_reference_t<TUP>>>;
   
   
+  
+  namespace { // apply to tuple-like : helpers...
+    
+    /** @internal invocation helper similar to C++17 — but preferring a custom `get` impl */
+    template<typename FUN, typename TUP, size_t...Idx>
+    constexpr decltype(auto)
+    __unpack_and_apply (FUN&& f, TUP&& tup, std::index_sequence<Idx...>)
+    {         // ▽▽▽ ADL
+      using std::get;
+      return std::invoke (std::forward<FUN> (f)
+                         ,get<Idx> (std::forward<TUP>(tup))...
+                         );
+    }
+    
+    
+    /** @internal invoke a metafunction with \a FUN and all element types from \a TUP */
+    template<template<typename...> class META, class FUN, class TUP>
+    struct _InvokeMetafunTup
+      {
+        using Tupl = std::decay_t<TUP>;
+        using Elms = typename ElmTypes<Tupl>::Seq;
+        using Args = typename Prepend<FUN, Elms>::Seq;
+        using Type = typename RebindVariadic<META, Args>::Type;
+      };
+    
+    template<class FUN, class TUP>
+    inline constexpr bool can_nothrow_invoke_tup = _InvokeMetafunTup<std::is_nothrow_invocable,FUN,TUP>::Type::value;
+  }
+  
+  /**
+   * Replacement for `std::apply` — yet applicable to _tuple-like custom types_.
+   * For unclear reasons, the standard chooses to reject such custom types, and
+   * only allows a fixed set of explicitly defined facilities from the Stdlib
+   * (tuple, pair, array, and some ranges stuff).
+   * @todo 6/2025 as a first step, this replicates the implementation from C++17;
+   *       the second step would be to constrain this to a concept `tuple_like`
+   */
+  template<class FUN, class TUP>
+  constexpr decltype(auto)
+  apply (FUN&& f, TUP&& tup)  noexcept (can_nothrow_invoke_tup<FUN,TUP> )
+  {
+    using Indices = std::make_index_sequence<std::tuple_size_v<std::remove_reference_t<TUP>>>;
+    
+    return __unpack_and_apply (std::forward<FUN> (f)
+                              ,std::forward<TUP> (tup)
+                              ,Indices{}
+                              );
+  }
+  
+  
   /**
    * Tuple iteration: perform some arbitrary operation on each element of a tuple.
    * @note the given functor must be generic, since each position of the tuple
@@ -87,7 +138,7 @@ namespace meta {
    *       then employ a fold expression with the comma operator.
    */
   template<class TUP, class FUN, typename = enable_if_Tuple<TUP>>
-  void
+  constexpr void
   forEach (TUP&& tuple, FUN fun)
   {
            std::apply ([&fun](auto&&... elms)
@@ -112,7 +163,7 @@ namespace meta {
    *          is used, which is guaranteed to evaluate from left to right.
    */
   template<class TUP, class FUN, typename = enable_if_Tuple<TUP>>
-  auto
+  constexpr auto
   mapEach (TUP&& tuple, FUN fun)
   {
     return std::apply ([&fun](auto&&... elms)

src/lib/p.hpp

@@ -31,6 +31,13 @@
  ** the corresponding operators on the pointee and by allowing to specify a base class smart-ptr
  ** as template parameter.
  **
+ ** @deprecated 2025 : smells like an overly zealous design, while fundamental traits of the
+ **             involved entities remain nebulous. Who is the »entity«? The pointer or the pointee?
+ **             Why do we even want to delegate relational operators, while we do not even know that
+ **             the target supports them? And why to we need an virtual equality? If these objects have
+ **             reference semantics, then a base class should compare the identity. And there should not
+ **             be any ordering on such elements. So the whole motivation of rolling a specialised
+ **             shard-ptr seems moot.                   /////////////////////////////////////////////////////TICKET #501 : clarify Placement and MObject identity
  ** @see asset.hpp
  ** @see custom-shared-ptr-test.cpp
  ** @see orderingofassetstest.cpp
@@ -94,11 +101,11 @@ namespace lib {
       
       
     private: /* === friend operators injected into enclosing namespace for ADL === */
-                                                                                          //////////////////TICKET #932 Clang is unable to fill in the default template argument. Resolved in newer versions of Clang. Temporary workaround: add second parameter B
+                                                                                          ///////////////////TICKET #932 Clang is unable to fill in the default template argument. Resolved in newer versions of Clang. Temporary workaround: add second parameter B
       template<typename _O_,typename B>
       friend inline bool
       operator== (P const& p, P<_O_, B> const& q) { return (p and q)? (*p == *q) : (!p and !q); }
-      
+                                                                                      ///////////////////////TICKET #501 : clarify Placement and MObject identity
       template<typename _O_,typename B>
       friend inline bool
       operator!= (P const& p, P<_O_, B> const& q) { return (p and q)? (*p != *q) : !(!p and !q); }

src/lib/random-draw.hpp

@@ -234,8 +234,8 @@ namespace lib {
               return Tar{floor (val)};
             }
         }                             //----headroom to accommodate low probabilities
-      static size_t constexpr QUANTISER   = 1 << 4 + util::ilog2 (Tar::maxVal()-Tar::minVal());
+      static constexpr size_t QUANTISER   = 1 << 4 + util::ilog2 (Tar::maxVal()-Tar::minVal());
-      static double constexpr CAP_EPSILON = 1/(2.0 * QUANTISER);
+      static constexpr double CAP_EPSILON = 1/(2.0 * QUANTISER);
       
       
       /** @internal draw from source of randomness */

src/lib/several-builder.hpp

@@ -147,7 +147,7 @@ namespace lib {
      * elements of type \a TY in memory _with proper alignment_.
      */
     template<typename TY>
-    size_t inline constexpr
+    inline constexpr size_t
     reqSiz()
       {
         size_t quant = alignof(TY);
@@ -159,7 +159,7 @@ namespace lib {
       }
     
     /** determine size of a reserve buffer to place with proper alignment */
-    size_t inline constexpr
+    inline constexpr size_t
     alignRes (size_t alignment)
       {
         return positiveDiff (alignment, alignof(void*));

src/lib/symbol.hpp

@@ -148,7 +148,7 @@ namespace lib {
        Symbol& operator= (Symbol &&)     = default;
        
        explicit operator bool()  const { return not empty(); }
-       bool empty()              const { return *this == BOTTOM or *this == EMPTY; }
+       bool empty()              const { return *this == BOTTOM.c() or *this == EMPTY.c(); }
        
        size_t
        length()  const

src/lib/time/time.cpp

@@ -285,7 +285,7 @@ namespace time {
   Duration
   FrameRate::duration() const
   {
-    if (0 == *this)
+    if (HALTED > *this)
       throw error::Logic ("Impossible to quantise to an zero spaced frame grid"
                          , error::LUMIERA_ERROR_BOTTOM_VALUE);
     

src/lib/time/timecode.cpp

@@ -451,28 +451,28 @@ namespace time {
   int
   HmsTC::getSecs() const
   {         /////////////////////////////////////////////////////////////////////////////////////////////////TICKET #750 we do not want numeric accessors her — rather we want Digxel members
-    return (raw_time_64(tpoint_) / TIME_SCALE_sec) % 60;
+    return (_raw (tpoint_) / TIME_SCALE_sec) % 60;
   }
   
   /** @deprecated 5/25 : no numeric computations in this class! use Digxel instead! */
   int
   HmsTC::getMins() const
   {
-    return (raw_time_64(tpoint_) / TIME_SCALE_sec / 60) % 60;
+    return (_raw (tpoint_) / TIME_SCALE_sec / 60) % 60;
   }
   
   /** @deprecated 5/25 : no numeric computations in this class! use Digxel instead! */
   int
   HmsTC::getHours() const
   {
-    return raw_time_64(tpoint_) / TIME_SCALE_sec / 60 / 60;
+    return _raw (tpoint_) / TIME_SCALE_sec / 60 / 60;
   }
   
   /** @deprecated 5/25 : no numeric computations in this class! use Digxel instead! */
   double
   HmsTC::getMillis() const
   {
-    return (raw_time_64(tpoint_) / TIME_SCALE_ms) % 1000;
+    return (_raw (tpoint_) / TIME_SCALE_ms) % 1000;
   }
   
   /** */

src/lib/time/timevalue.hpp

@@ -191,7 +191,7 @@ namespace time {
       static TimeValue buildRaw_(raw_time_64);
       
       /** @internal diagnostics */
-      operator std::string ()  const;
+      explicit operator std::string()  const;
       
       /** @return is in-domain, not a boundary value */
       bool isRegular()  const;
@@ -265,8 +265,6 @@ namespace time {
           return *this;
         }
       
-      /// Support mixing with plain 64bit int arithmetics
-      operator raw_time_64()  const { return t_; }
       /// Support for micro-tick precise time arithmetics
       operator FSecs()  const { return FSecs{t_, TimeValue::SCALE}; }
       
@@ -342,7 +340,7 @@ namespace time {
            );
       
       /** @internal diagnostics */
-      operator std::string ()  const;
+      explicit operator std::string()  const;
       
       /** convenience start for time calculations */
       TimeVar operator+ (TimeValue const& tval)  const { return TimeVar(*this) + tval; }
@@ -405,7 +403,7 @@ namespace time {
       Offset stretchedByFloatFactor    (double)  const;
       
       /** @internal diagnostics, indicating ∆ */
-      operator std::string ()  const;
+      explicit operator std::string()  const;
       
       // Supporting sign flip
       Offset operator- ()  const;
@@ -522,7 +520,7 @@ namespace time {
       
       
       /** @internal diagnostics */
-      operator std::string ()  const;
+      explicit operator std::string()  const;
 
       /// Supporting backwards use as offset
       Offset operator- ()  const;
@@ -651,7 +649,7 @@ namespace time {
       void accept (Mutation const&);
       
       /** @internal diagnostics */
-      operator std::string ()  const;
+      explicit operator std::string()  const;
       
       /// Supporting extended total order, based on start and interval length
       friend bool operator== (TimeSpan const& t1, TimeSpan const& t2)  { return t1.t_==t2.t_ && t1.dur_==t2.dur_; }
@@ -689,7 +687,10 @@ namespace time {
       /** duration of one frame */
       Duration duration() const;
       
-      operator std::string() const;
+      /** derive total ordering from base class */
+      std::strong_ordering operator<=>(FrameRate const&) const = default;
+      
+      explicit operator std::string() const;
     };
   
   /** convenient conversion to duration in fractional seconds */

src/lib/util-quant.hpp

@@ -30,7 +30,7 @@
 namespace util {
   
   template<typename N>
-  inline bool constexpr
+  inline constexpr bool
   isPow2 (N n)
     {
       return n > 0 and !(n & (n-1));

src/lib/util.hpp

@@ -40,9 +40,9 @@ namespace std {// forward declarations to avoid pervasive includes
   class set;
   
   template<typename IT, typename V>
-  IT find (IT, IT, V const&);
+  constexpr IT find (IT, IT, V const&);
   template<typename IT, typename V>
-  IT remove (IT, IT, V const&);
+  constexpr IT remove (IT, IT, V const&);
 }
 
 
@@ -57,21 +57,21 @@ namespace util {
   
   
   template <class NUM>
-  inline int constexpr
+  inline constexpr int
   sgn (NUM n)
   {
     return (n==0)? 0 :((n<0)? -1:+1 );
   }
   
   template <class N1, class N2>
-  inline N1 constexpr
+  inline constexpr N1
   min (N1 n1, N2 n2)
   {
     return n2 < n1? N1(n2) : n1;
   }
   
   template <class N1, class N2>
-  inline N1 constexpr
+  inline constexpr N1
   max (N1 n1, N2 n2)
   {
     return n1 < n2? N1(n2) : n1;
@@ -79,7 +79,7 @@ namespace util {
   
   /** cut a numeric value to be >=0 */
   template <typename NUM>
-  inline NUM constexpr
+  inline constexpr NUM
   noneg (NUM val)
   {
     return (0<val? val : 0);
@@ -87,7 +87,7 @@ namespace util {
   
   /** force a numeric to be within bounds, inclusively */
   template <typename NUM, typename NB>
-  inline NUM constexpr
+  inline constexpr NUM
   limited (NB lowerBound, NUM val, NB upperBound)
   {
     return min ( max (val, lowerBound)
@@ -95,7 +95,7 @@ namespace util {
   }
   
   template <typename NUM, typename NB>
-  inline bool constexpr
+  inline constexpr bool
   isLimited (NB lowerBound, NUM val, NB upperBound)
   {
     return lowerBound <= val
@@ -103,7 +103,7 @@ namespace util {
   }
   
   template <typename UN, typename N2>
-  inline UN constexpr
+  inline constexpr UN
   positiveDiff (N2 newVal, UN refVal)
   {
     return UN(newVal) > refVal? UN(newVal) - refVal

src/stage/ctrl/ui-dispatcher.hpp

@@ -113,8 +113,8 @@ namespace ctrl {
         : queue_{}
         , dispatcher_{}
         {
-          dispatcher_.connect(
+          dispatcher_.connect([=,this]
-                         [=]() {try {
+                               {try {
                                       queue_.invoke();
                                     }
                                   catch (std::exception& problem)

src/stage/notification-service.cpp

@@ -85,7 +85,7 @@ namespace stage {
   void
   NotificationService::dispatchMsg (ID uiElement, lib::diff::GenNode&& uiMessage)
   {
-    dispatch_->event ([=]()
+    dispatch_->event ([=,this]
                       {
                         ctrl::BusTerm::mark (uiElement, uiMessage);
                       });
@@ -136,7 +136,7 @@ namespace stage {
   void
   NotificationService::mutate (ID uiElement, MutationMessage&& diff)
   {
-    dispatch_->event ([=]()
+    dispatch_->event ([=,this]
                       { // apply and consume diff message stored within closure
                         this->change (uiElement, move(unConst(diff)));
                       });

src/stage/widget/timecode-widget.cpp

@@ -231,7 +231,7 @@ namespace widget {
     ms_seconds_ebox.set_can_focus(true);
     
     
-    auto connect_motion_event = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_motion_event = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_motion_notify_event), fieldID);
         guiElm.signal_motion_notify_event().connect (handlerSlot);
@@ -249,7 +249,7 @@ namespace widget {
     connect_motion_event (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_button_press = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_button_press = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_button_press_event), fieldID);
         guiElm.signal_button_press_event().connect (handlerSlot);
@@ -267,7 +267,7 @@ namespace widget {
     connect_button_press (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_button_release = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_button_release = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_button_release_event), fieldID);
         guiElm.signal_button_release_event().connect (handlerSlot);
@@ -285,7 +285,7 @@ namespace widget {
     connect_button_release (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_scroll_event = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_scroll_event = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_button_scroll_event), fieldID);
         guiElm.signal_scroll_event().connect (handlerSlot);
@@ -303,7 +303,7 @@ namespace widget {
     connect_scroll_event (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_key_press = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_key_press = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_key_press_event), fieldID);
         guiElm.signal_key_press_event().connect (handlerSlot);
@@ -321,7 +321,7 @@ namespace widget {
     connect_key_press (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_key_release = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_key_release = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_key_release_event), fieldID);
         guiElm.signal_key_release_event().connect (handlerSlot);
@@ -339,7 +339,7 @@ namespace widget {
     connect_key_release (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_focus_gain = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_focus_gain = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_focus_gain_event), fieldID);
         guiElm.signal_focus_in_event().connect (handlerSlot);
@@ -357,7 +357,7 @@ namespace widget {
     connect_focus_gain (ms_seconds_ebox, MS_Seconds);
     
     
-    auto connect_focus_loss = [=](Gtk::EventBox& guiElm, Field fieldID)
+    auto connect_focus_loss = [=,this](Gtk::EventBox& guiElm, Field fieldID)
       {
         auto handlerSlot = bind (mem_fun(this, &TimeCode::field_focus_loss_event), fieldID);
         guiElm.signal_focus_out_event().connect (handlerSlot);
@@ -1108,7 +1108,7 @@ namespace widget {
         if (frames  != 0 &&  frames * drag_accum < (_raw(current_time())))
           {
             // minus because up is negative in computer-land
-            pos = TimeValue (floor (pos - drag_accum * frames));
+            pos = TimeValue (floor (_raw(pos) - drag_accum * frames));
             set (pos, false);
           }
         else

src/stage/workspace/dock-area.cpp

@@ -136,7 +136,7 @@ namespace workspace {
   bool
   DockArea::hasPanel (const int description_index)
   {
-    return util::has_any (panels_, [=](panel::Panel* panel)
+    return util::has_any (panels_, [&](panel::Panel* panel)
                                     {
                                       return getPanelType(panel) == description_index;
                                     });

src/stage/workspace/panel-manager.cpp

@@ -131,7 +131,7 @@ namespace workspace {
   bool
   PanelManager::hasPanel (const int description_index)
   {
-    return util::has_any (panels_, [=](panel::Panel* panel)
+    return util::has_any (panels_, [&](panel::Panel* panel)
                                     {
                                       return getPanelType(panel) == description_index;
                                     });

src/steam/control/steam-dispatcher.cpp

@@ -356,7 +356,7 @@ namespace control {
     
     runningLoop_ =
          make_unique<DispatcherLoop>(
-            [=](string* problemIndicator)
+            [=,this](string* problemIndicator)
                 { // when the Session thread ends....
                   SteamDispatcher::endRunningLoopState();
                   termNotification (problemIndicator);

src/steam/engine/param-weaving-pattern.hpp

@@ -307,6 +307,8 @@ namespace engine {
             {
               builder.emplaceParamDataBlock (&block(), turnoutSys);
             }
+          ///////////////OOO
+          Feed()= default;
         };
       
       

src/steam/mobject/mobject.hpp

@@ -37,7 +37,6 @@
 #include "lib/p.hpp"
 #include "lib/time/timevalue.hpp"
 
-#include <boost/operators.hpp>
 #include <string>
 
 
@@ -69,8 +68,7 @@ namespace mobject {
    */
   class MObject
     : public Buildable,
-      util::NonCopyable,
+      util::NonCopyable
-      boost::equality_comparable< MObject >
     {
     protected:
       typedef lib::time::Duration Duration;
@@ -97,12 +95,21 @@ namespace mobject {
       /** MObject self-test (usable for asserting) */
       virtual bool isValid()  const =0;
       
-      virtual Duration& getLength() =0;                                           ////////////////////TICKET #448
+      virtual Duration& getLength() =0;                                           ///////////////////////////TICKET #448
       
-      virtual bool operator== (const MObject& oo)  const =0;  ///< needed for handling by lumiera::P
+      /** needed for handling by lumiera::P
+       * @deprecated 2025 this seems not well motivated. lumiera::P was created
+       *  to support comparisons, and now we do not know how to implement them,
+       *  and thus we make the operation virtual. Are MObjects conceived as
+       *  having value semantics? For reference semantics, comparing the
+       *  »identity« should be sufficient
+       * @note 2025 changed to a predicate to cope with C++20 reversed operators.
+       */
+      virtual bool isEquivalentTo (const MObject& oo)  const =0;     ////////////////////////////////////////TICKET #501 : clarify Placement and MObject identity
+      
+      friend bool operator== (MObject const& o1, MObject const& o2) { return o1.isEquivalentTo(o2); }
       
     protected:
-      
       virtual string initShortID()  const =0;
       
     };

src/steam/mobject/session/abstractmo.cpp

@@ -31,9 +31,10 @@ namespace session {
   /** default/fallback implementation of equality
    *  using literal object identity (same address).
    *  Required to enable handling by lumiera::P
+   * @deprecated 2025, see comment in MObject    ////////////////////////////////////////////////////////////TICKET #501 : clarify Placement and MObject identity
    */
   bool
-  AbstractMO::operator== (const MObject& oo)  const
+  AbstractMO::isEquivalentTo (const MObject& oo)  const
   {
     return (this == &oo);
   }

src/steam/mobject/session/abstractmo.hpp

@@ -59,7 +59,7 @@ namespace session {
           return length_; 
         }
       
-      bool operator== (const MObject& oo)  const;
+      bool isEquivalentTo (const MObject& oo)  const override;
       
     protected:
       void

src/steam/play/output-director.cpp

@@ -94,7 +94,7 @@ namespace play {
       {
         shutdown_initiated_ = true;
         launchDetached ("Output shutdown supervisor"
-                       ,[=]{
+                       ,[=,this]{
                                   bringDown (completedSignal);
                                 });
       }

src/vault/gear/engine-observer.hpp

@@ -59,7 +59,7 @@ namespace gear {
   class EngineEvent
     {
     protected:
-      static size_t constexpr RAW_SIZ = 3;
+      static constexpr size_t RAW_SIZ = 3;
       using Storage = std::array<int64_t, RAW_SIZ>;
       
       template<class DAT>

src/vault/gear/scheduler-commutator.hpp

@@ -82,9 +82,7 @@ namespace gear {
   using lib::time::FSecs;
   using lib::time::Time;
   using std::atomic;
-  using std::memory_order::memory_order_relaxed;
+  using std::memory_order;
-  using std::memory_order::memory_order_acquire;
-  using std::memory_order::memory_order_release;
   using std::chrono_literals::operator ""us;
   using std::chrono::microseconds;
   
@@ -129,8 +127,8 @@ namespace gear {
         {
           ThreadID expect_noThread;                   // expect no one else to be in...
           return groomingToken_.compare_exchange_strong (expect_noThread, thisThread()
-                                                        ,memory_order_acquire // success also constitutes an acquire barrier
+                                                        ,memory_order::acquire // success also constitutes an acquire barrier
-                                                        ,memory_order_relaxed // failure has no synchronisation ramifications
+                                                        ,memory_order::relaxed // failure has no synchronisation ramifications
                                                         );
         }
       
@@ -145,7 +143,7 @@ namespace gear {
         {          // expect that this thread actually holds the Grooming-Token
           REQUIRE (groomingToken_.load(memory_order_relaxed) == thisThread());
           const ThreadID noThreadHoldsIt;
-          groomingToken_.store (noThreadHoldsIt, memory_order_release);
+          groomingToken_.store (noThreadHoldsIt, memory_order::release);
         }
       
       /**

src/vault/gear/work-force.cpp

@@ -66,7 +66,7 @@ namespace gear {
   work::performRandomisedSpin (size_t stepping, size_t randFact)
   {
     size_t degree = CONTEND_SOFT_FACTOR * (1+randFact) * stepping;
-    for (volatile size_t i=0; i<degree; ++i) {/*SPIN*/}
+    for (volatile size_t i=0; i<degree; ) { i=i+1; /*SPIN*/}
   }
   
   /**

tests/basics/call-queue-test.cpp

@@ -197,7 +197,7 @@ namespace test{
                                 for (uint i=0; i<cnt; ++i)
                                   {
                                     uint increment = rand_.i(MAX_RAND_INCMT);
-                                    queue.feed ([=]() { countConsumerCall(increment); });
+                                    queue.feed ([=,this]{ countConsumerCall(increment); });
                                     producerSum += increment;
                                     usleep (delay);
                                     queue.invoke();  // NOTE: dequeue one functor added during our sleep

tests/basics/time/quantiser-basics-test.cpp

@@ -112,7 +112,7 @@ namespace test{
           quant (int testPoint)
             {
               TimeVar quantised = this->gridLocal(TimeValue(testPoint));
-              return int(quantised);
+              return _raw(quantised);
             }
         };
       

tests/basics/time/time-basics-test.cpp

@@ -101,7 +101,7 @@ namespace test{
           CHECK (!(var <  ref) );
           CHECK ( (var >  ref) );
           
-          raw_time_64 rat(var);
+          raw_time_64 rat = _raw(var);
           CHECK (!(rat == ref) );
           CHECK ( (rat != ref) );
           CHECK ( (rat >= ref) );

tests/basics/time/time-parsing-test.cpp

@@ -62,9 +62,9 @@ namespace test{
           {
             TimeValue parsed = FMT::parse (timeSpec_, *grid_);
             CHECK (parsed == expected, "parsing '%s' resulted in %s instead of %s"
-                                     , cStr(timeSpec_)
+                                     , timeSpec_.c_str()
-                                     , cStr(Time(parsed))
+                                     , string{Time(parsed)}.c_str()
-                                     , cStr(Time(expected)));
+                                     , string{Time(expected)}.c_str());
           }
         
         void

tests/basics/time/time-value-test.cpp

@@ -142,7 +142,7 @@ namespace test{
           CHECK (var < Time::MAX);
           CHECK (var > Time::MIN);
           
-          raw_time_64 raw (var);
+          raw_time_64 raw = _raw(var);
           CHECK (raw == org);
           CHECK (raw >  org - two);
           

tests/core/steam/asset/identity-of-assets-test.cpp

@@ -83,7 +83,7 @@ namespace test {
           
           AssetManager& aMang = AssetManager::instance();
           CHECK (aMang.getAsset (mm1->getID()) == mm2); // record of mm1 was replaced by mm2
-          CHECK (aMang.getAsset (mm2->getID()) == mm2);
+          CHECK (aMang.getAsset (mm2->getID()) == mm2);                              ////////////////////////TICKET #501 : clarify Placement and MObject identity
           
           CHECK (aMang.known (mm1->getID()));
           CHECK (aMang.known (mm2->getID()));

tests/core/steam/control/command-argument-test.cpp

@@ -82,7 +82,7 @@ namespace test    {
             return element_;
           }
         
-        operator string()  const { return element_; }
+        operator string()  const { return util::toString(element_); }
         
         
         friend bool

tests/core/steam/mobject/builder/builder-tool-test.cpp

@@ -68,7 +68,7 @@ namespace test    {
             {
               Placement<Clip>& pC = getPlacement<Clip>();
               cout << "Clip on media : "<< pC->getMedia() <<"\n";
-              CHECK (pC->operator==(c));
+              CHECK (pC->isEquivalentTo(c));
               log_ = string (pC);
             }
           void treat (AbstractMO&)

tests/library/custom-shared-ptr-test.cpp

@@ -22,8 +22,6 @@
 
 #include "lib/p.hpp"
 
-#include <boost/operators.hpp>
-
 
 
 namespace lib {
@@ -37,15 +35,13 @@ namespace test{
   
   
   struct X
-    : boost::totally_ordered<X>
     {
       long x_;
       
-      X(long x=0)  : x_(x) {}
+      explicit X(long x=0) : x_(x) {}
       operator long () { return x_; }
       
-      bool operator<  (const X& ox)  const { return x_ <  ox.x_; }
+      std::strong_ordering operator<=>(X const&) const = default;
-      bool operator== (const X& ox)  const { return x_ == ox.x_; }
       
       virtual ~X() {} // using RTTI
     };

tests/library/format-helper-test.cpp

@@ -27,6 +27,7 @@
 #include <string>
 
 
+using lumiera::error::Fatal;
 using lib::transformIterator;
 using lib::iter_stl::snapshot;
 using lib::iter_stl::eachElm;
@@ -53,6 +54,12 @@ namespace test {
         operator string()  const { return "hey Joe!"; }
       };
     
+    class Bomb
+      {
+      public:
+        operator string()  const { throw Fatal{"mistake"}; }
+      };
+    
     
     
     class AutoCounter
@@ -110,7 +117,7 @@ namespace test {
           CHECK (toString (chatterer)   ==   "hey Joe!"_expect);
           
           CHECK (toString (&chatterer)  ==  "↗hey Joe!"_expect); // pointer indicated
-          CHECK (toString (nullptr)     ==          "↯"_expect); // runtime exception, caught
+          CHECK (toString (Bomb{})      ==          "↯"_expect); // runtime exception, caught
           
           CHECK (toString (true)        ==       "true"_expect); // special handling for bool
           CHECK (toString (2+2 == 5)    ==      "false"_expect);

tests/stage/bus-term-test.cpp

@@ -660,7 +660,7 @@ namespace test {
                */
               SessionThread(function<void(DiffSource*)> notifyGUI)
                 : ThreadJoinable{"BusTerm_test: asynchronous diff mutation"
-                                , [=]
+                                , [this,notifyGUI]
                                     {
                                       uint cnt       = randGen_.i(MAX_RAND_BORGS);
                                       for (uint i=0; i<cnt; ++i)
@@ -719,8 +719,9 @@ namespace test {
               usleep (100);
               uiDispatcher.invoke();
             }
-          session.join();
+          auto ok = session.join();
           //------end-multithreaded-mutation---
+          CHECK (ok);
           
           // on rare occasions we (consumer thread)
           // prematurely empty the queue...

tests/stage/test/test-nexus.cpp

@@ -213,7 +213,7 @@ namespace test{
               commandHandler_ = newHandler;
             else
               commandHandler_ =
-                [=](GenNode const& cmd)
+                [this](GenNode const& cmd)
                   {
                     log_.warn(_Fmt("NOT handling command-message %s in test-mode") % cmd);
                   };
@@ -226,7 +226,7 @@ namespace test{
               stateMarkHandler_ = newHandler;
             else
               stateMarkHandler_ =
-                [=](ID subject, GenNode const& mark)
+                [this](ID subject, GenNode const& mark)
                   {
                     log_.warn(_Fmt("NOT handling state-mark %s passed from %s in test-mode")
                                                             % mark         % subject);

tests/vault/gear/stress-test-rig.hpp

@@ -209,7 +209,7 @@ namespace test {
       bool showRes  = true;     ///< print result data
       bool showRef  = true;     ///< calculate single threaded reference time
       
-      static uint constexpr REPETITIONS{20};
+      static constexpr uint REPETITIONS{20};
 
       BlockFlowAlloc bFlow{};
       EngineObserver watch{};

tests/vault/gear/test-chain-load.hpp

@@ -1394,7 +1394,7 @@ namespace test {
           for ( ; 0 < round; --round)
             lib::hash::combine (scree,scree);
           sink = scree;
-          sink++;
+          sink = sink + 1;
         }
       
       void
@@ -1408,7 +1408,7 @@ namespace test {
             for (size_t i=0; i<memBlock.size()-1; ++i)
               memBlock[i+1] += memBlock[i];
           sink = *memBlock.back();
-          sink++;
+          sink = sink + 1;
         }
       
       double