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ruby--ruby/id_table.h
卜部昌平 eb92159d72 Revert https://github.com/ruby/ruby/pull/2486
This reverts commits: 10d6a3aca7 8ba48c1b85 fba8627dc1 dd883de5ba
6c6a25feca 167e6b48f1 7cb96d41a5 3207979278 595b3c4fdd 1521f7cf89
c11c5e69ac cf33608203 3632a812c0 f56506be0d 86427a3219 .

The reason for the revert is that we observe ABA problem around
inline method cache.  When a cache misshits, we search for a
method entry.  And if the entry is identical to what was cached
before, we reuse the cache.  But the commits we are reverting here
introduced situations where a method entry is freed, then the
identical memory region is used for another method entry.  An
inline method cache cannot detect that ABA.

Here is a code that reproduce such situation:

```ruby
require 'prime'

class << Integer
  alias org_sqrt sqrt
  def sqrt(n)
    raise
  end

  GC.stress = true
  Prime.each(7*37){} rescue nil # <- Here we populate CC
  class << Object.new; end

  # These adjacent remove-then-alias maneuver
  # frees a method entry, then immediately
  # reuses it for another.
  remove_method :sqrt
  alias sqrt org_sqrt
end

Prime.each(7*37).to_a # <- SEGV
```
2019-10-03 12:45:24 +09:00

34 lines
1.5 KiB
C

#ifndef RUBY_ID_TABLE_H
#define RUBY_ID_TABLE_H 1
#include "ruby/ruby.h"
struct rb_id_table;
/* compatible with ST_* */
enum rb_id_table_iterator_result {
ID_TABLE_CONTINUE = ST_CONTINUE,
ID_TABLE_STOP = ST_STOP,
ID_TABLE_DELETE = ST_DELETE,
ID_TABLE_REPLACE = ST_REPLACE,
ID_TABLE_ITERATOR_RESULT_END
};
struct rb_id_table *rb_id_table_create(size_t size);
void rb_id_table_free(struct rb_id_table *tbl);
void rb_id_table_clear(struct rb_id_table *tbl);
size_t rb_id_table_size(const struct rb_id_table *tbl);
size_t rb_id_table_memsize(const struct rb_id_table *tbl);
int rb_id_table_insert(struct rb_id_table *tbl, ID id, VALUE val);
int rb_id_table_lookup(struct rb_id_table *tbl, ID id, VALUE *valp);
int rb_id_table_delete(struct rb_id_table *tbl, ID id);
typedef enum rb_id_table_iterator_result rb_id_table_update_callback_func_t(ID *id, VALUE *val, void *data, int existing);
typedef enum rb_id_table_iterator_result rb_id_table_foreach_func_t(ID id, VALUE val, void *data);
typedef enum rb_id_table_iterator_result rb_id_table_foreach_values_func_t(VALUE val, void *data);
void rb_id_table_foreach(struct rb_id_table *tbl, rb_id_table_foreach_func_t *func, void *data);
void rb_id_table_foreach_with_replace(struct rb_id_table *tbl, rb_id_table_foreach_func_t *func, rb_id_table_update_callback_func_t *replace, void *data);
void rb_id_table_foreach_values(struct rb_id_table *tbl, rb_id_table_foreach_values_func_t *func, void *data);
#endif /* RUBY_ID_TABLE_H */