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Memory leak when duplicating identhash

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[Bug #20145]

Before this commit, both copy_compare_by_id and hash_copy will create a
copy of the ST table, so the ST table created in copy_compare_by_id will
be leaked.

    h = { 1 => 2 }.compare_by_identity

    10.times do
      1_000_000.times do
        h.select { false }
      end

      puts `ps -o rss= -p #{$$}`
    end

Before:

    110736
    204352
    300272
    395520
    460704
    476736
    542000
    604704
    682624
    770528

After:

    15504
    16048
    16144
    16256
    16320
    16320
    16752
    16752
    16752
    16752
This commit is contained in:
Peter Zhu 2024-01-03 15:59:37 -05:00
parent 542011ff68
commit 6c252912af
2 changed files with 19 additions and 1 deletions
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10
hash.c
View File

@ -1558,7 +1558,15 @@ hash_copy(VALUE ret, VALUE hash)
static VALUE
hash_dup_with_compare_by_id(VALUE hash)
{
return hash_copy(copy_compare_by_id(rb_hash_new(), hash), hash);
VALUE dup = hash_alloc_flags(rb_cHash, 0, Qnil, RHASH_ST_TABLE_P(hash));
if (RHASH_ST_TABLE_P(hash)) {
RHASH_SET_ST_FLAG(dup);
}
else {
RHASH_UNSET_ST_FLAG(dup);
}
return hash_copy(dup, hash);
}
static VALUE

10
test/ruby/test_hash.rb
View File

@ -1458,6 +1458,16 @@ class TestHash < Test::Unit::TestCase
assert_predicate(h.dup, :compare_by_identity?, bug8703)
end
def test_compare_by_identy_memory_leak
assert_no_memory_leak([], "", "#{<<~"begin;"}\n#{<<~'end;'}", "[Bug #20145]", rss: true)
begin;
h = { 1 => 2 }.compare_by_identity
1_000_000.times do
h.select { false }
end
end;
end
def test_same_key
bug9646 = '[ruby-dev:48047] [Bug #9646] Infinite loop at Hash#each'
h = @cls[a=[], 1]