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include/ruby/internal/intern/gc.h: add doxygen

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Must not be a bad idea to improve documents. [ci skip]
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卜部昌平 2021-04-21 14:10:12 +09:00
parent 990a6c789a
commit ba42d35dd0
Notes: git 2021-09-10 20:01:29 +09:00
1 changed files with 352 additions and 19 deletions
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371
include/ruby/internal/intern/gc.h
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@ -20,37 +20,370 @@
* extension libraries. They could be written in C++98.
* @brief Public APIs related to ::rb_mGC.
*/
#include "ruby/internal/config.h"
#ifdef STDC_HEADERS
# include <stddef.h> /* size_t */
#endif
#if HAVE_SYS_TYPES_H
# include <sys/types.h> /* ssize_t */
#endif
#include "ruby/internal/attr/cold.h"
#include "ruby/internal/attr/noreturn.h"
#include "ruby/internal/attr/nonnull.h"
#include "ruby/internal/attr/pure.h"
#include "ruby/internal/dllexport.h"
#include "ruby/internal/value.h"
#include "ruby/backward/2/attributes.h"
RBIMPL_SYMBOL_EXPORT_BEGIN()
/* gc.c */
COLDFUNC NORETURN(void rb_memerror(void));
PUREFUNC(int rb_during_gc(void));
void rb_gc_mark_locations(const VALUE*, const VALUE*);
void rb_mark_tbl(struct st_table*);
void rb_mark_tbl_no_pin(struct st_table*);
void rb_mark_set(struct st_table*);
void rb_mark_hash(struct st_table*);
RBIMPL_ATTR_COLD()
RBIMPL_ATTR_NORETURN()
/**
* Triggers out-of-memory error. If possible it raises ::rb_eNoMemError. But
* because we are running out of memory that is not always doable. This
* function tries hard to show something, but ultimately can die silently.
*
* @exception rb_eNoMemError Raises it if possible.
*/
void rb_memerror(void);
RBIMPL_ATTR_PURE()
/**
* Queries if the GC is busy.
*
* @retval 0 It isn't.
* @retval 1 It is.
*/
int rb_during_gc(void);
RBIMPL_ATTR_NONNULL((1))
/**
* Marks objects between the two pointers. This is one of the GC utility
* functions that you can call when you design your own
* ::rb_data_type_struct::dmark.
*
* @pre Continuous memory region from `start` to `end` shall be fully
* addressable.
* @param[out] start Pointer to an array of objects.
* @param[out] end Pointer that terminates the array of objects.
* @post Objects from `start` to `end`, both inclusive, are marked.
*
* @internal
*
* `end` can be NULL... But that just results in no-op.
*/
void rb_gc_mark_locations(const VALUE *start, const VALUE *end);
/**
* Identical to rb_mark_hash(), except it marks only values of the table and
* leave their associated keys unmarked. This is one of the GC utility
* functions that you can call when you design your own
* ::rb_data_type_struct::dmark.
*
* @warning Of course it can break GC. Leave it unused if unsure.
* @param[in] tbl A table to mark.
* @post Values stored in `tbl` are marked.
*/
void rb_mark_tbl(struct st_table *tbl);
/**
* Identical to rb_mark_tbl(), except it marks objects using
* rb_gc_mark_movable(). This is one of the GC utility functions that you can
* call when you design your own ::rb_data_type_struct::dmark.
*
* @warning Of course it can break GC. Leave it unused if unsure.
* @param[in] tbl A table to mark.
* @post Values stored in `tbl` are marked.
*/
void rb_mark_tbl_no_pin(struct st_table *tbl);
/**
* Identical to rb_mark_hash(), except it marks only keys of the table and
* leave their associated values unmarked. This is one of the GC utility
* functions that you can call when you design your own
* ::rb_data_type_struct::dmark.
*
* @warning Of course it can break GC. Leave it unused if unsure.
* @param[in] tbl A table to mark.
* @post Keys stored in `tbl` are marked.
*/
void rb_mark_set(struct st_table *tbl);
/**
* Marks keys and values associated inside of the given table. This is one of
* the GC utility functions that you can call when you design your own
* ::rb_data_type_struct::dmark.
*
* @param[in] tbl A table to mark.
* @post Objects stored in `tbl` are marked.
*/
void rb_mark_hash(struct st_table *tbl);
/**
* Updates references inside of tables. After you marked values using
* rb_mark_tbl_no_pin(), the objects inside of the table could of course be
* moved. This function is to fixup those references. You can call this from
* your ::rb_data_type_struct::dcompact.
*
* @param[out] ptr A table that potentially includes moved references.
* @post Moved references, if any, are corrected.
*/
void rb_gc_update_tbl_refs(st_table *ptr);
void rb_gc_mark_maybe(VALUE);
void rb_gc_mark(VALUE);
void rb_gc_mark_movable(VALUE);
VALUE rb_gc_location(VALUE);
void rb_gc_force_recycle(VALUE);
/**
* Identical to rb_gc_mark(), except it allows the passed value be a
* non-object. For instance pointers to different type of memory regions are
* allowed here. Such values are silently ignored. This is one of the GC
* utility functions that you can call when you design your own
* ::rb_data_type_struct::dmark.
*
* @param[out] obj A possible object.
* @post `obj` is marked, if possible.
*/
void rb_gc_mark_maybe(VALUE obj);
/**
* Marks an object. This is one of the GC utility functions that you can call
* when you design your own ::rb_data_type_struct::dmark.
*
* @param[out] obj Arbitrary Ruby object.
* @post `obj` is marked.
*/
void rb_gc_mark(VALUE obj);
/**
* Maybe this is the only function provided for C extensions to control the
* pinning of objects, so let us describe it in detail. These days Ruby's GC
* is copying. As far as an object's physical address is guaranteed unused, it
* can move around the object space. Our GC engine rearranges these objects
* after it reclaims unreachable objects from our object space, so that the
* space is compact (improves memory locality). This is called the
* "compaction" phase, and works well most of the time... as far as there are
* no C extensions. C extensions complicate the scenario because Ruby core
* cannot detect any use of the physical address of an object inside of C
* functions. In order to prevent memory corruptions, objects observable from
* C extensions are "pinned"; they stick to where they are born until they die,
* just in case any C extensions touch their raw pointers. This variant of
* scheme is called "Mostly-Copying" garbage collector. Authors of C
* extensions, however, can extremely carefully write them to become
* compaction-aware. To do so avoid referring to a Ruby object from inside of
* your struct in the first place. But if that is not possible, use this
* function from your ::rb_data_type_struct::dmark then. This way objects
* marked using it are considered movable. If you chose this way you have to
* manually fix up locations of such moved pointers using rb_gc_location().
*
* @see Bartlett, Joel F., "Compacting Garbage Collection with Ambiguous
* Roots", ACM SIGPLAN Lisp Pointers Volume 1 Issue 6 pp. 3-12,
* April-May-June, 1988. https://doi.org/10.1145/1317224.1317225
*
* @param[in] obj Object that is movable.
* @post Values stored in `tbl` are marked.
*/
void rb_gc_mark_movable(VALUE obj);
/**
* Finds a new "location" of an object. An object can be moved on compaction.
* This function projects its new abode, or just returns the passed object if
* not moved. This is one of the GC utility functions that you can call when
* you design your own ::rb_data_type_struct::dcompact.
*
* @param[in] obj An object, possibly already moved to somewhere else.
* @return An object, which holds the current contents of former `obj`.
*/
VALUE rb_gc_location(VALUE obj);
/**
* Asserts that the passed object is no longer needed. Such objects are
* reclaimed sooner or later so this function is not mandatory. But sometimes
* you can know from your application knowledge that an object is surely dead
* at some point. Calling this as a hint can be a polite way.
*
* @param[out] obj Object, dead.
* @pre `obj` have never been passed to this function before.
* @post `obj` could be invalidated.
* @warning It is a failure to pass an object multiple times to this
* function.
*/
void rb_gc_force_recycle(VALUE obj);
/**
* Triggers a GC process. This was the only GC entry point that we had at the
* beginning. Over time our GC evolved. Now what this function does is just a
* very simplified variation of the entire GC algorithms. A series of
* procedures kicked by this API is called a "full" GC.
*
* - It immediately scans the entire object space to sort the dead.
* - It immediately reclaims any single dead bodies to reuse later.
*
* It is worth noting that the procedures above do not include evaluations of
* finalisers. They run later.
*
* @internal
*
* Finalisers are deferred until we can handle interrupts. See
* `rb_postponed_job_flush` in vm_trace.c.
*
* Of course there are GC that are not "full". For instance this one and the
* GC which runs when we are running out of memory are different. See
* `gc_profile_record_flag` defined in gc.c for the kinds of GC.
*
* In spite of the name this is not what everything that a GC can trigger. As
* of writing it seems this function does not trigger compaction. But this
* might change in future.
*/
void rb_gc(void);
void rb_gc_copy_finalizer(VALUE,VALUE);
/**
* Copy&paste an object's finaliser to another. This is one of the GC utility
* functions that you can call when you design your own `initialize_copy`,
* `initialize_dup`, `initialize_clone`.
*
* @param[out] dst Destination object.
* @param[in] src Source object.
* @post `dst` and `src` share the same finaliser.
*
* @internal
*
* But isn't it easier for you to call super, and let `Object#intialize_copy`
* call this function instead?
*/
void rb_gc_copy_finalizer(VALUE dst, VALUE src);
/**
* (Re-) enables GC. This makes sense only after you called rb_gc_disable().
*
* @retval RUBY_Qtrue GC was disabled before.
* @retval RUBY_Qfalse GC was enabled before.
* @post GC is enabled.
*
* @internal
*
* This is one of such exceptional functions that does not raise both Ruby
* exceptions and C++ exceptions.
*/
VALUE rb_gc_enable(void);
/**
* Disables GC. This prevents automatic GC runs when the process is running
* out of memory. Such situations shall result in rb_memerror(). However this
* does not prevent users from manually invoking rb_gc(). That should work.
* People abused this by disabling GC at the beginning of an event loop,
* process events without GC overheads, then manually force reclaiming garbage
* at the bottom of the loop. However because our GC is now much smarter than
* just calling rb_gc(), this technique is proven to be sub-optimal these days.
* It is believed that there is currently practically no needs of this
* function.
*
* @retval RUBY_Qtrue GC was disabled before.
* @retval RUBY_Qfalse GC was enabled before.
* @post GC is disabled.
*/
VALUE rb_gc_disable(void);
/**
* Identical to rb_gc(), except the return value.
*
* @return Always returns ::RUBY_Qnil.
*/
VALUE rb_gc_start(void);
VALUE rb_define_finalizer(VALUE, VALUE);
VALUE rb_undefine_finalizer(VALUE);
/**
* Assigns a finaliser for an object. Each objects can have objects (typically
* blocks) that run immediately after that object dies. They are called
* finalisers of an object. This function associates a finaliser object with a
* target object.
*
* @note Note that finalisers run _after_ the object they finalise dies. You
* cannot for instance call its methods.
* @note If your finaliser references the object it finalises that object
* loses any chance to become a garbage; effectively leaks memory until
* the end of the process.
*
* @param[in] obj Target to finalise.
* @param[in] block Something `call`able.
* @exception rb_eRuntimeError Somehow `obj` cannot have finalisers.
* @exception rb_eFrozenError `obj` is frozen.
* @exception rb_eArgError `block` doesn't respond to `call`.
* @return The passed `block`.
* @post `block` runs after `obj` dies.
*/
VALUE rb_define_finalizer(VALUE obj, VALUE block);
/**
* Modifies the object so that it has no finalisers at all. This function is
* mainly provided for symmetry. No practical usages can be thought of.
*
* @param[out] obj Object to clear its finalisers.
* @exception rb_eFrozenError `obj` is frozen.
* @return The passed `obj`.
* @post `obj` has no finalisers.
* @note There is no way to undefine a specific part of many finalisers
* that `obj` could have. All you can do is to clear them all.
*/
VALUE rb_undefine_finalizer(VALUE obj);
/**
* Identical to rb_gc_stat(), with "count" parameter.
*
* @return Lifetime total number of runs of GC.
*/
size_t rb_gc_count(void);
size_t rb_gc_stat(VALUE);
VALUE rb_gc_latest_gc_info(VALUE);
void rb_gc_adjust_memory_usage(ssize_t);
/**
* Obtains various GC related profiles. The parameter can be either a Symbol
* or a Hash. If a Hash is passed, it is filled with everything currently
* available. If a Symbol is passed just that portion is returned.
*
* Possible variations of keys you can pass here change from version to
* version. You can get the list of known keys by passing an empty hash and
* let it be filled.
*
* @param[in,out] key_or_buf A Symbol, or a Hash.
* @exception rb_eTypeError Neither Symbol nor Hash.
* @exception rb_eFrozenError Frozen hash is passed.
* @return In case a Hash is passed it returns 0. Otherwise the
* profile value associated with the given key is returned.
* @post In case a Hash is passed it is filled with values.
*/
size_t rb_gc_stat(VALUE key_or_buf);
/**
* Obtains various info regarding the most recent GC run. This includes for
* instance the reason of the GC. The parameter can be either a Symbol or a
* Hash. If a Hash is passed, it is filled with everything currently
* available. If a Symbol is passed just that portion is returned.
*
* Possible variations of keys you can pass here change from version to
* version. You can get the list of known keys by passing an empty hash and
* let it be filled.
*
* @param[in,out] key_or_buf A Symbol, or a Hash.
* @exception rb_eTypeError Neither Symbol nor Hash.
* @exception rb_eFrozenError Frozen hash is passed.
* @return In case a Hash is passed it returns that hash. Otherwise
* the profile value associated with the given key is returned.
* @post In case a Hash is passed it is filled with values.
*/
VALUE rb_gc_latest_gc_info(VALUE key_or_buf);
/**
* Informs that there are external memory usages. Our GC runs when we are
* running out of memory. The amount of memory, however, can increase/decrease
* behind-the-scene. For instance DLLs can allocate memories using `mmap(2)`
* etc, which are opaque to us. Registering such external allocations using
* this function enables proper detection of how much memories an object used
* as a whole. That will trigger GCs more often than it would otherwise. You
* can also pass negative numbers here, to indicate that such external
* allocations are gone.
*
* @param[in] diff Amount of memory increased(+)/decreased(-).
*/
void rb_gc_adjust_memory_usage(ssize_t diff);
RBIMPL_SYMBOL_EXPORT_END()