In commit d42b9ffb206, an optimization was introduced that can speed up Regexp#match by 15% when it matches with strings of different encodings. This optimization, however, does not work across ractors. To fix this, we only use the optimization if no ractors have been started. In the future, we could use atomics for the reference counting if we find it's needed and if it's more performant. The backtrace of the misbehaving native thread: ``` * frame #0: 0x0000000189c94388 libsystem_kernel.dylib`__pthread_kill + 8 frame #1: 0x0000000189ccd88c libsystem_pthread.dylib`pthread_kill + 296 frame #2: 0x0000000189bd6c60 libsystem_c.dylib`abort + 124 frame #3: 0x0000000189adb174 libsystem_malloc.dylib`malloc_vreport + 892 frame #4: 0x0000000189adec90 libsystem_malloc.dylib`malloc_report + 64 frame #5: 0x0000000189ae321c libsystem_malloc.dylib`___BUG_IN_CLIENT_OF_LIBMALLOC_POINTER_BEING_FREED_WAS_NOT_ALLOCATED + 32 frame #6: 0x00000001001c3be4 ruby`onig_free_body(reg=0x000000012d84b660) at regcomp.c:5663:5 frame #7: 0x00000001001ba828 ruby`rb_reg_prepare_re(re=4748462304, str=4748451168) at re.c:1680:13 frame #8: 0x00000001001bac58 ruby`rb_reg_onig_match(re=4748462304, str=4748451168, match=(ruby`reg_onig_search [inlined] rbimpl_RB_TYPE_P_fastpath at value_type.h:349:14 ruby`reg_onig_search [inlined] rbimpl_rstring_getmem at rstring.h:391:5 ruby`reg_onig_search at re.c:1781:5), args=0x000000013824b168, regs=0x000000013824b150) at re.c:1708:20 frame #9: 0x00000001001baefc ruby`rb_reg_search_set_match(re=4748462304, str=4748451168, pos=<unavailable>, reverse=0, set_backref_str=1, set_match=0x0000000000000000) at re.c:1809:27 frame #10: 0x00000001001bae80 ruby`rb_reg_search0(re=<unavailable>, str=<unavailable>, pos=<unavailable>, reverse=<unavailable>, set_backref_str=<unavailable>, match=<unavailable>) at re.c:1861:12 [artificial] frame #11: 0x0000000100230b90 ruby`rb_pat_search0(pat=<unavailable>, str=<unavailable>, pos=<unavailable>, set_backref_str=<unavailable>, match=<unavailable>) at string.c:6619:16 [artificial] frame #12: 0x00000001002287f4 ruby`rb_str_sub_bang [inlined] rb_pat_search(pat=4748462304, str=4748451168, pos=0, set_backref_str=1) at string.c:6626:12 frame #13: 0x00000001002287dc ruby`rb_str_sub_bang(argc=1, argv=0x00000001381280d0, str=4748451168) at string.c:6668:11 frame #14: 0x000000010022826c ruby`rb_str_sub ``` You can reproduce this by running: ``` RUBY_TESTOPTS="--name=/test_str_capitalize/" make test-all TESTS=test/ruby/test_m17n.comb ``` However, you need to run it with multiple ractors at once. Co-authored-by: jhawthorn <[email protected]>