The method incorrectly ignored its first argument and treated the second argument as offset and the third as count.
This change makes the first argument be treated as offset and the second as count.
Also fix incorrect block parameter in comments.
For `JSON.generate` and `JSON::State#generate_new`, don't copy
generate_json_data::depth to JSON_Generator_State::depth.
In `JSON.generate`, the JSON_Generator_State is on the stack and
discarded anyway. In `JSON::State#generate_new`, we copy the struct to
avoid mutating the original one.
https://github.com/ruby/json/commit/873b29ea34
Since we do not run a Ractor barrier before forking, it's possible that
another other Ractor is halfway through allocating an object during forking.
This may lead to allocated_objects_count being off by one.
For example, the following script reproduces the bug:
100.times do |i|
Ractor.new(i) do |j|
10000.times do |i|
"#{j}-#{i}"
end
Ractor.receive
end
pid = fork { GC.verify_internal_consistency }
_, status = Process.waitpid2 pid
raise unless status.success?
end
We need to run with `taskset -c 1` to force it to use a single CPU core
to more consistenly reproduce the bug:
heap_pages_final_slots: 1, total_freed_objects: 16628
test.rb:8: [BUG] inconsistent live slot number: expect 19589, but 19588.
ruby 4.0.0dev (2025-11-25T03:06:55Z master 55892f5994) +PRISM [x86_64-linux]
-- Control frame information -----------------------------------------------
c:0007 p:---- s:0029 e:000028 l:y b:---- CFUNC :verify_internal_consistency
c:0006 p:0004 s:0025 e:000024 l:n b:---- BLOCK test.rb:8 [FINISH]
c:0005 p:---- s:0022 e:000021 l:y b:---- CFUNC :fork
c:0004 p:0012 s:0018 E:0014c0 l:n b:---- BLOCK test.rb:8
c:0003 p:0024 s:0011 e:000010 l:y b:0001 METHOD <internal:numeric>:257
c:0002 p:0005 s:0006 E:001730 l:n b:---- EVAL test.rb:1 [FINISH]
c:0001 p:0000 s:0003 E:001d20 l:y b:---- DUMMY [FINISH]
-- Ruby level backtrace information ----------------------------------------
test.rb:1:in '<main>'
<internal:numeric>:257:in 'times'
test.rb:8:in 'block in <main>'
test.rb:8:in 'fork'
test.rb:8:in 'block (2 levels) in <main>'
test.rb:8:in 'verify_internal_consistency'
-- Threading information ---------------------------------------------------
Total ractor count: 1
Ruby thread count for this ractor: 1
-- C level backtrace information -------------------------------------------
ruby(rb_print_backtrace+0x14) [0x61b67ac48b60] vm_dump.c:1105
ruby(rb_vm_bugreport) vm_dump.c:1450
ruby(rb_bug_without_die_internal+0x5f) [0x61b67a818a28] error.c:1098
ruby(rb_bug) error.c:1116
ruby(gc_verify_internal_consistency_+0xbdd) [0x61b67a83d8ed] gc/default/default.c:5186
ruby(gc_verify_internal_consistency+0x2d) [0x61b67a83d960] gc/default/default.c:5241
ruby(rb_gc_verify_internal_consistency) gc/default/default.c:8950
ruby(gc_verify_internal_consistency_m) gc/default/default.c:8966
ruby(vm_call_cfunc_with_frame_+0x10d) [0x61b67a9e50fd] vm_insnhelper.c:3902
ruby(vm_sendish+0x111) [0x61b67a9eeaf1] vm_insnhelper.c:6124
ruby(vm_exec_core+0x84) [0x61b67aa07434] insns.def:903
ruby(vm_exec_loop+0xa) [0x61b67a9f8155] vm.c:2811
ruby(rb_vm_exec) vm.c:2787
ruby(vm_yield_with_cref+0x90) [0x61b67a9fd2ea] vm.c:1865
ruby(vm_yield) vm.c:1873
ruby(rb_yield) vm_eval.c:1362
ruby(rb_protect+0xef) [0x61b67a81fe6f] eval.c:1154
ruby(rb_f_fork+0x16) [0x61b67a8e98ab] process.c:4293
ruby(rb_f_fork) process.c:4284
