Complex smobs are created by deriving from Smob<Classname>.
+ However, this is not sufficient when classes with their own
+ protectable elements are derived from the Complex base class. This
+ is because initialization order is a tricky thing: once a base class
+ calls smobify_self () in its constructor, further allocations during
+ construction of base class and derived classes might lead to
+ mark_smob calls on the object under construction. When those call a
+ virtual function like derived_mark, the virtual function
+ corresponding to the incompletely initialized object of derived
+ class type is likely to be called.
+
+ The order of initialization of an object consists in calling the
+ constructors of virtual base classes, then of non-virtual base
+ classes, then initializing all data members.
+
+ As a result, the constructor of a derived class comes too late for
+ initialization of data members that may be accessed in the
+ derived_mark kind of functions.
+
+ Such data members are consequently moved into Preinit_* classes
+ which come before the smobifying base class in derivation order and
+ construct the contained data members in a state suitable for
+ derived_mark calls.
+
+
CALLING INTERFACE
Common global functions for accessing C++ smob objects:
debugging purposes. If the class does not define this function,
the output will be #<Classname> when printing.
- - a static const type_p_name_[] string set to something like
+ - a static const * const type_p_name_ string set to something like
"ly:grob?". When provided, an accordingly named function for
checking for the given smob type will be available in Scheme.
// Most default functions are do-nothings. void init() will
// recognize their address when not overriden and will then refrain
// altogether from passing the the respective callbacks to GUILE.
+
SCM mark_smob (void) const;
static SCM mark_trampoline (SCM); // Used for calling mark_smob
static size_t free_smob (SCM obj);
static int print_trampoline (SCM, SCM, scm_print_state *);
static void smob_proc_init (scm_t_bits) { };
- // type_p_name_ has to be defined in the Super class, either with a
- // static const char [] string or as a null pointer of type const
- // char *. We used to provide a default here for convenience, but
- // battling the various conflicting C++ standards was too much of a
- // hassle.
+ // Define type_p_name_ in the Super class as a const char * const.
+ // Without such definition it defaults to 0, producing no predicate.
+
+ static const char * const type_p_name_; // = 0
// LY_DECLARE_SMOB_PROC is used in the Super class definition for
// making a smob callable like a function. Its first argument is a