Prevent ObjectSpace.count_objects from allocating extra arrays #13906
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`ObjectSpace.count_objects` could cause an unintended array allocation.
It returns a hash like `{ :T_ARRAY => 100, :T_STRING => 100, ... }`, so
it creates the key symbol (e.g., `:T_STRING`) for the first time. On
rare occations, this symbol creation internally allocates a new array
for symbol management.
This led to a problematic side effect where calling `count_objects`
twice in a row could produce inconsistent results: the first call would
trigger the hidden array allocation, and the second call would then
report an increased count for `:T_ARRAY`.
This behavior caused test failures in `test/ruby/test_allocation.rb`,
which performs a baseline measurement before an operation and then
asserts the exact number of new allocations.
https://rubyci.s3.amazonaws.com/openbsd-current/ruby-master/log/20250716T053005Z.fail.html.gz
> 1) Failure:
> TestAllocation::ProcCall::WithBlock#test_ruby2_keywords [...]:
> Expected 1 array allocations for "r2k.(1, a: 2, &block)", but 2 arrays allocated.
This change resolves the issue by pre-interning all key symbols used by
`ObjectSpace.count_objects` before its counting. This eliminates the
side effect and ensures the stability of allocation-sensitive tests.
Co-authored-by: Koichi Sasada <ko1@atdot.net>
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ObjectSpace.count_objectscould cause an unintended array allocation. It returns a hash like{ :T_ARRAY => 100, :T_STRING => 100, ... }, so it creates the key symbol (e.g.,:T_STRING) for the first time. On rare occations, this symbol creation internally allocates a new array for symbol management.This led to a problematic side effect where calling
count_objectstwice in a row could produce inconsistent results: the first call would trigger the hidden array allocation, and the second call would then report an increased count for:T_ARRAY.This behavior caused test failures in
test/ruby/test_allocation.rb, which performs a baseline measurement before an operation and then asserts the exact number of new allocations.https://rubyci.s3.amazonaws.com/openbsd-current/ruby-master/log/20250716T053005Z.fail.html.gz
This change resolves the issue by pre-interning all key symbols used by
ObjectSpace.count_objectsbefore its counting. This eliminates the side effect and ensures the stability of allocation-sensitive tests.