class.c: descendants must not cause GC until the result array is created
Follow up of 428227472fc6563046d8138aab17f07bef6af753. The previous fix uses `rb_ary_new_from_values` to create the result array, but it may trigger the GC. This second try is to create the result array by `rb_ary_new_capa` before the second iteration, and assume that `rb_ary_push` does not trigger GC. This assumption is very fragile, so should be improved in future. [Bug #18282] [Feature #14394]
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2021-11-10 10:08:59 +09:00
22
class.c
22
class.c
@ -29,6 +29,7 @@
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#include "internal/variable.h"
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#include "ruby/st.h"
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#include "vm_core.h"
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#include "gc.h"
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#define id_attached id__attached__
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@ -1338,7 +1339,7 @@ rb_mod_ancestors(VALUE mod)
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struct subclass_traverse_data
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{
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VALUE *buffer;
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VALUE buffer;
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long count;
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long maxcount;
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};
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@ -1349,8 +1350,9 @@ class_descendants_recursive(VALUE klass, VALUE v)
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struct subclass_traverse_data *data = (struct subclass_traverse_data *) v;
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if (BUILTIN_TYPE(klass) == T_CLASS && !FL_TEST(klass, FL_SINGLETON)) {
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if (data->buffer && data->count < data->maxcount) {
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data->buffer[data->count] = klass;
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if (data->buffer && data->count < data->maxcount && !rb_objspace_garbage_object_p(klass)) {
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// assumes that this does not cause GC as long as the length does not exceed the capacity
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rb_ary_push(data->buffer, klass);
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}
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data->count++;
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}
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@ -1378,24 +1380,26 @@ class_descendants_recursive(VALUE klass, VALUE v)
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VALUE
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rb_class_descendants(VALUE klass)
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{
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struct subclass_traverse_data data = { NULL, 0, -1 };
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struct subclass_traverse_data data = { Qfalse, 0, -1 };
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// estimate the count of subclasses
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rb_class_foreach_subclass(klass, class_descendants_recursive, (VALUE) &data);
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// the following allocation may cause GC which may change the number of subclasses
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data.buffer = ALLOC_N(VALUE, data.count);
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data.buffer = rb_ary_new_capa(data.count);
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data.maxcount = data.count;
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data.count = 0;
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size_t gc_count = rb_gc_count();
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// enumerate subclasses
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rb_class_foreach_subclass(klass, class_descendants_recursive, (VALUE) &data);
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VALUE ary = rb_ary_new_from_values(data.count, data.buffer);
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if (gc_count != rb_gc_count()) {
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rb_bug("GC must not occur during the subclass iteration of Class#descendants");
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}
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free(data.buffer);
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return ary;
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return data.buffer;
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}
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static void
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@ -761,4 +761,12 @@ class TestClass < Test::Unit::TestCase
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100000.times { Class.new(c) }
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assert(c.descendants.size <= 100000)
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end
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def test_descendants_gc_stress
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10000.times do
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c = Class.new
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100.times { Class.new(c) }
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assert(c.descendants.size <= 100)
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end
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end
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end
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