include/ruby/internal/rgengc.h: add dosygen

Must not be a bad idea to improve documents. [ci skip]

2 files changed, 265 insertions, 20 deletions

diff --git a/include/ruby/internal/rgengc.h b/include/ruby/internal/rgengc.h
index a41e75c877..7ea04442f6 100644
--- a/include/ruby/internal/rgengc.h
+++ b/include/ruby/internal/rgengc.h
@@ -22,106 +22,250 @@
  * @see        Sasada,  K.,  "Gradual  write-barrier   insertion  into  a  Ruby
  *             interpreter",   in  proceedings   of   the   2019  ACM   SIGPLAN
  *             International  Symposium on  Memory Management  (ISMM 2019),  pp
- *             115-121, 2019. https://doi.org/10.1145/3315573.3329986
+ *             115-121, 2019.  https://doi.org/10.1145/3315573.3329986
  */
 #include "ruby/internal/attr/artificial.h"
+#include "ruby/internal/attr/maybe_unused.h"
 #include "ruby/internal/attr/pure.h"
 #include "ruby/internal/dllexport.h"
 #include "ruby/internal/special_consts.h"
 #include "ruby/internal/stdbool.h"
 #include "ruby/internal/value.h"
 #include "ruby/assert.h"
-#include "ruby/backward/2/attributes.h"
 
+/**
+ * @private
+ *
+ * @deprecated  This macro once was a thing in the old days, but makes no sense
+ *              any  longer today.   Exists  here  for backwards  compatibility
+ *              only.  You can safely forget about it.
+ */
 #undef USE_RGENGC
 #define USE_RGENGC 1
 
+/**
+ * @private
+ *
+ * This is  a compile-time flag  to enable/disable incremental GC  feature.  It
+ * has to  be set at  the time  ruby itself compiles.   Makes no sense  for 3rd
+ * parties.  It is safe  for them to set this though;  that just doesn't change
+ * anything.
+ */
 #ifndef USE_RINCGC
 # define USE_RINCGC 1
 #endif
 
+/**
+ * @deprecated  This macro seems  broken.  Setting this to  anything other than
+ *              zero just doesn't compile.  We need to KonMari.
+ */
 #ifndef USE_RGENGC_LOGGING_WB_UNPROTECT
 # define USE_RGENGC_LOGGING_WB_UNPROTECT 0
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RArray.  It has to be set  at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_ARRAY
 # define RGENGC_WB_PROTECTED_ARRAY 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RHash.  It has  to be set at the time  ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_HASH
 # define RGENGC_WB_PROTECTED_HASH 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RStruct.  It has to be set at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_STRUCT
 # define RGENGC_WB_PROTECTED_STRUCT 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RString.  It has to be set at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_STRING
 # define RGENGC_WB_PROTECTED_STRING 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RObject.  It has to be set at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_OBJECT
 # define RGENGC_WB_PROTECTED_OBJECT 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RRegexp.  It has to be set at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_REGEXP
 # define RGENGC_WB_PROTECTED_REGEXP 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RClass.  It has to be set  at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_CLASS
 # define RGENGC_WB_PROTECTED_CLASS 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RFloat.  It has to be set  at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_FLOAT
 # define RGENGC_WB_PROTECTED_FLOAT 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RComplex.   It has  to be  set at  the time  ruby itself  compiles.
+ * Makes no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_COMPLEX
 # define RGENGC_WB_PROTECTED_COMPLEX 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RRational.  It  has to  be set  at the  time ruby  itself compiles.
+ * Makes no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_RATIONAL
 # define RGENGC_WB_PROTECTED_RATIONAL 1
 #endif
 
+/**
+ * @private
+ *
+ * This  is   a  compile-time   flag  to   enable/disable  write   barrier  for
+ * struct ::RBignum.  It has to be set at the time ruby itself compiles.  Makes
+ * no sense for 3rd parties.
+ */
 #ifndef RGENGC_WB_PROTECTED_BIGNUM
 # define RGENGC_WB_PROTECTED_BIGNUM 1
 #endif
 
+/**
+ * @private
+ *
+ * @deprecated  This macro once was a thing in the old days, but makes no sense
+ *              any  longer today.   Exists  here  for backwards  compatibility
+ *              only.  You can safely forget about it.
+ *
+ * @internal
+ *
+ * @shyouhei doesn't think anybody uses this right now.
+ */
 #ifndef RGENGC_WB_PROTECTED_NODE_CREF
 # define RGENGC_WB_PROTECTED_NODE_CREF 1
 #endif
 
 /**
- * @name Write barrier (WB) interfaces:
- * @{
+ * @defgroup rgengc Write barrier (WB) interfaces:
  *
  * @note The following  core interfaces can  be changed in the  future.  Please
  *       catch up if you want to insert WB into C-extensions correctly.
+ *
+ * @{
  */
 
 /**
- * WB for new  reference from `a' to  `b'. Write `b' into `*slot'.  `slot' is a
- * pointer in `a'.
+ * Declaration of a "back" pointer.  This  is a write barrier for new reference
+ * from  "old"  generation  to  "young" generation.   It  writes  `young`  into
+ * `*slot`, which is a pointer inside of `old`.
+ *
+ * @param[in]   old    An old object.
+ * @param[in]   slot   A pointer inside of `old`.
+ * @param[out]  young  A young object.
  */
-#define RB_OBJ_WRITE(a, slot, b) \
-    RBIMPL_CAST(rb_obj_write((VALUE)(a), (VALUE *)(slot), (VALUE)(b), __FILE__, __LINE__))
+#define RB_OBJ_WRITE(old, slot, young) \
+    RBIMPL_CAST(rb_obj_write((VALUE)(old), (VALUE *)(slot), (VALUE)(young), __FILE__, __LINE__))
+
 /**
- * WB for new  reference from `a' to  `b'.  This doesn't write  any values, but
- * only  a WB  declaration.  `oldv'  is replaced  value with  `b' (not  used in
- * current Ruby).
+ * Identical to #RB_OBJ_WRITE(), except it doesn't write any values, but only a
+ * WB declaration.   `oldv` is  replaced value  with `b`  (not used  in current
+ * Ruby).
+ *
+ * @param[in]   old    An old object.
+ * @param[in]   oldv   An object previously stored inside of `old`.
+ * @param[out]  young  A young object.
  */
-#define RB_OBJ_WRITTEN(a, oldv, b) \
-    RBIMPL_CAST(rb_obj_written((VALUE)(a), (VALUE)(oldv), (VALUE)(b), __FILE__, __LINE__))
+#define RB_OBJ_WRITTEN(old, oldv, young) \
+    RBIMPL_CAST(rb_obj_written((VALUE)(old), (VALUE)(oldv), (VALUE)(young), __FILE__, __LINE__))
 /** @} */
 
-#define OBJ_PROMOTED_RAW RB_OBJ_PROMOTED_RAW
-#define OBJ_PROMOTED     RB_OBJ_PROMOTED
-#define OBJ_WB_UNPROTECT RB_OBJ_WB_UNPROTECT
+#define OBJ_PROMOTED_RAW RB_OBJ_PROMOTED_RAW /**< @old{RB_OBJ_PROMOTED_RAW} */
+#define OBJ_PROMOTED     RB_OBJ_PROMOTED     /**< @old{RB_OBJ_PROMOTED} */
+#define OBJ_WB_UNPROTECT RB_OBJ_WB_UNPROTECT /**< @old{RB_OBJ_WB_UNPROTECT} */
 
+/**
+ * Asserts that the passed object is  not fenced by write barriers.  Objects of
+ * such  property do  not contribute  to  generational GCs.   They are  scanned
+ * always.
+ *
+ * @param[out]  x  An object that would not be protected by the barrier.
+ */
 #define RB_OBJ_WB_UNPROTECT(x) rb_obj_wb_unprotect(x, __FILE__, __LINE__)
+
+/**
+ * Identical  to #RB_OBJ_WB_UNPROTECT(),  except it  can also  assert that  the
+ * given object is of given type.
+ *
+ * @param[in]   type  One of `ARRAY`, `STRING`, etc.
+ * @param[out]  obj   An object of `type` that would not be protected.
+ *
+ * @internal
+ *
+ * @shyouhei doesn't understand why this has to be visible from extensions.
+ */
 #define RB_OBJ_WB_UNPROTECT_FOR(type, obj) \
     (RGENGC_WB_PROTECTED_##type ? OBJ_WB_UNPROTECT(obj) : obj)
+
+/**
+ * @private
+ *
+ * This is an implementation detail of rb_obj_wb_unprotect().  People don't use
+ * it directly.
+ */
 #define RGENGC_LOGGING_WB_UNPROTECT rb_gc_unprotect_logging
 
 /** @cond INTERNAL_MACRO */
@@ -130,15 +274,51 @@
 /** @endcond */
 
 RBIMPL_SYMBOL_EXPORT_BEGIN()
-void rb_gc_writebarrier(VALUE a, VALUE b);
+/**
+ * This  is  the  implementation  of  #RB_OBJ_WRITE().   People  don't  use  it
+ * directly.
+ *
+ * @param[in]   old    An object that points to `young`.
+ * @param[out]  young  An object that is referenced from `old`.
+ */
+void rb_gc_writebarrier(VALUE old, VALUE young);
+
+/**
+ * This is the  implementation of #RB_OBJ_WB_UNPROTECT().  People  don't use it
+ * directly.
+ *
+ * @param[out] obj  An object that does not participate in WB.
+ */
 void rb_gc_writebarrier_unprotect(VALUE obj);
+
 #if USE_RGENGC_LOGGING_WB_UNPROTECT
+/**
+ * @private
+ *
+ * This  is  the   implementation  of  #RGENGC_LOGGING_WB_UNPROTECT().   People
+ * don't use it directly.
+ *
+ * @param[in]  objptr    Don't  know why  this  is  a pointer  to  void but  in
+ *                       reality this is  a pointer to an object  that is about
+ *                       to be un-protected.
+ * @param[in]  filename  Pass C's `__FILE__` here.
+ * @param[in]  line      Pass C's `__LINE__` here.
+ */
 void rb_gc_unprotect_logging(void *objptr, const char *filename, int line);
 #endif
+
 RBIMPL_SYMBOL_EXPORT_END()
 
 RBIMPL_ATTR_PURE_UNLESS_DEBUG()
 RBIMPL_ATTR_ARTIFICIAL()
+/**
+ * This  is the  implementation  of #RB_OBJ_PROMOTED().   People  don't use  it
+ * directly.
+ *
+ * @param[in]  obj    An object to query.
+ * @retval     true   The object is "promoted".
+ * @retval     false  The object is young.  Have not experienced GC at all.
+ */
 static inline bool
 RB_OBJ_PROMOTED_RAW(VALUE obj)
 {
@@ -148,6 +328,17 @@ RB_OBJ_PROMOTED_RAW(VALUE obj)
 
 RBIMPL_ATTR_PURE_UNLESS_DEBUG()
 RBIMPL_ATTR_ARTIFICIAL()
+/**
+ * Tests if the object is "promoted" -- that is, whether the object experienced
+ * one or more GC marks.
+ *
+ * @param[in]  obj    An object to query.
+ * @retval     true   The object is "promoted".
+ * @retval     false  The object is young.  Have not experienced GC at all.
+ * @note       Hello, is anyone actively calling this function?  @shyouhei have
+ *             never seen  any actual usages  outside of the  GC implementation
+ *             itself.
+ */
 static inline bool
 RB_OBJ_PROMOTED(VALUE obj)
 {
@@ -159,8 +350,22 @@ RB_OBJ_PROMOTED(VALUE obj)
     }
 }
 
+/**
+ * This is the  implementation of #RB_OBJ_WB_UNPROTECT().  People  don't use it
+ * directly.
+ *
+ * @param[out]  x         An object that does not participate in WB.
+ * @param[in]   filename  C's `__FILE__` of the caller function.
+ * @param[in]   line      C's `__LINE__` of the caller function.
+ * @return      x
+ */
 static inline VALUE
-rb_obj_wb_unprotect(VALUE x, RB_UNUSED_VAR(const char *filename), RB_UNUSED_VAR(int line))
+rb_obj_wb_unprotect(
+    VALUE x,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    const char *filename,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    int line)
 {
 #if USE_RGENGC_LOGGING_WB_UNPROTECT
     RGENGC_LOGGING_WB_UNPROTECT(RBIMPL_CAST((void *)x), filename, line);
@@ -169,8 +374,29 @@ rb_obj_wb_unprotect(VALUE x, RB_UNUSED_VAR(const char *filename), RB_UNUSED_VAR(
     return x;
 }
 
+/**
+ * @private
+ *
+ * This  is  the implementation  of  #RB_OBJ_WRITTEN().   People don't  use  it
+ * directly.
+ *
+ * @param[in]   a         An old object.
+ * @param[in]   oldv      An object previously stored inside of `old`.
+ * @param[out]  b         A young object.
+ * @param[in]   filename  C's `__FILE__` of the caller function.
+ * @param[in]   line      C's `__LINE__` of the caller function.
+ * @return      a
+ */
 static inline VALUE
-rb_obj_written(VALUE a, RB_UNUSED_VAR(VALUE oldv), VALUE b, RB_UNUSED_VAR(const char *filename), RB_UNUSED_VAR(int line))
+rb_obj_written(
+    VALUE a,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    VALUE oldv,
+    VALUE b,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    const char *filename,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    int line)
 {
 #if USE_RGENGC_LOGGING_WB_UNPROTECT
     RGENGC_LOGGING_OBJ_WRITTEN(a, oldv, b, filename, line);
@@ -183,8 +409,26 @@ rb_obj_written(VALUE a, RB_UNUSED_VAR(VALUE oldv), VALUE b, RB_UNUSED_VAR(const
     return a;
 }
 
+/**
+ * @private
+ *
+ * This  is  the  implementation  of  #RB_OBJ_WRITE().   People  don't  use  it
+ * directly.
+ *
+ * @param[in]   a         An old object.
+ * @param[in]   slot      A pointer inside of `old`.
+ * @param[out]  b         A young object.
+ * @param[in]   filename  C's `__FILE__` of the caller function.
+ * @param[in]   line      C's `__LINE__` of the caller function.
+ * @return      a
+ */
 static inline VALUE
-rb_obj_write(VALUE a, VALUE *slot, VALUE b, RB_UNUSED_VAR(const char *filename), RB_UNUSED_VAR(int line))
+rb_obj_write(
+    VALUE a, VALUE *slot, VALUE b,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    const char *filename,
+    RBIMPL_ATTR_MAYBE_UNUSED()
+    int line)
 {
 #ifdef RGENGC_LOGGING_WRITE
     RGENGC_LOGGING_WRITE(a, slot, b, filename, line);
diff --git a/template/Doxyfile.tmpl b/template/Doxyfile.tmpl
index 0d356ca03a..9cb537c66a 100644
--- a/template/Doxyfile.tmpl
+++ b/template/Doxyfile.tmpl
@@ -2230,6 +2230,7 @@ PREDEFINED            += NOINLINE(_)=_
 PREDEFINED            += NORETURN(_)=_
 PREDEFINED            += PRINTF_ARGS(_,__,___)=_
 PREDEFINED            += PUREFUNC(_)=_
+PREDEFINED            += RB_UNUSED_VAR(_)=_
 PREDEFINED            += RUBY_EXTERN=extern
 PREDEFINED            += RUBY_FUNC_EXPORTED=
 PREDEFINED            += RUBY_FUNC_NONNULL(__,_)=_