[tasaka1@localhost ruby]$ gdb --args ruby-mri -I. -e 'require "skf" ; Skf.convert("-s", [164, 162].pack("C*"))'
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Reading symbols from ruby-mri...
Reading symbols from /usr/lib/debug/usr/bin/ruby-mri-2.7.2-135.fc33.x86_64.debug...
(gdb) r
Starting program: /usr/bin/ruby-mri -I. -e require\ \"skf\"\ \;\ Skf.convert\(\"-s\",\ \[164,\ 162\].pack\(\"C\*\"\)\)
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
free(): double free detected in tcache 2

Program received signal SIGABRT, Aborted.
__GI_raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:49
49	  return ret;
Missing separate debuginfos, use: dnf debuginfo-install gmp-6.2.0-5.fc33.x86_64 libxcrypt-4.4.17-1.fc33.x86_64
(gdb) bt
#0  __GI_raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:49
#1  0x00007ffff7aa68a4 in __GI_abort () at abort.c:79
#2  0x00007ffff7afff27 in __libc_message (action=<optimized out>, fmt=<optimized out>) at ../sysdeps/posix/libc_fatal.c:155
#3  0x00007ffff7b07c1c in malloc_printerr (str=str@entry=0x7ffff7c147a8 "free(): double free detected in tcache 2") at malloc.c:5389
#4  0x00007ffff7b096ec in _int_free (av=0x7ffff7c44a00 <main_arena>, p=0x5555557100a0, have_lock=0) at malloc.c:4232
#5  0x00007fffe67a3479 in convert (optstr=optstr@entry=0x5555557501d0, cstr=0x5555557100b0) at skf_convert_f_wrap.c:3168
#6  0x00007fffe67a3517 in _wrap_convert (argc=<optimized out>, argv=0x7fffea1f2048, self=<optimized out>) at skf_convert_f_wrap.c:3486
#7  0x00007ffff7e69692 in vm_call_cfunc_with_frame (empty_kw_splat=<optimized out>, cd=<optimized out>, calling=<optimized out>, reg_cfp=<optimized out>, ec=<optimized out>) at vm_insnhelper.c:2514
#8  vm_call_cfunc (ec=0x55555555b610, reg_cfp=<optimized out>, calling=<optimized out>, cd=0x555555896bd0) at vm_insnhelper.c:2539
#9  0x00007ffff7e5dd46 in vm_sendish (ec=0x55555555b610, reg_cfp=0x7fffea2f1fa0, cd=0x555555896bd0, block_handler=<optimized out>, method_explorer=<optimized out>) at vm_insnhelper.c:4023
#10 0x00007ffff7e6ddfc in vm_exec_core (ec=0x2, initial=140737488344880) at insns.def:801
#11 0x00007ffff7e7395c in rb_vm_exec (ec=0x55555555b610, mjit_enable_p=1) at vm.c:1929
#12 0x00007ffff7cf80b0 in rb_ec_exec_node (ec=ec@entry=0x55555555b610, n=n@entry=0x5555558f0020) at eval.c:278
#13 0x00007ffff7cfc498 in ruby_run_node (n=0x5555558f0020) at eval.c:336
#14 0x000055555555510b in main (argc=<optimized out>, argv=<optimized out>) at ./main.c:50
(gdb) up
#1  0x00007ffff7aa68a4 in __GI_abort () at abort.c:79
79	      raise (SIGABRT);
(gdb) 
#2  0x00007ffff7afff27 in __libc_message (action=<optimized out>, fmt=<optimized out>) at ../sysdeps/posix/libc_fatal.c:155
155	    abort ();
(gdb) 
#3  0x00007ffff7b07c1c in malloc_printerr (str=str@entry=0x7ffff7c147a8 "free(): double free detected in tcache 2") at malloc.c:5389
5389	  __libc_message (do_abort, "%s\n", str);
(gdb) 
#4  0x00007ffff7b096ec in _int_free (av=0x7ffff7c44a00 <main_arena>, p=0x5555557100a0, have_lock=0) at malloc.c:4232
4232			  malloc_printerr ("free(): double free detected in tcache 2");
(gdb) 
#5  0x00007fffe67a3479 in convert (optstr=optstr@entry=0x5555557501d0, cstr=0x5555557100b0) at skf_convert_f_wrap.c:3168
3168	    if (cstr != NULL) free(cstr);
(gdb) list
3163	    };
3164	
3165	    if (lwlstr->sstr != NULL) free(lwlstr->sstr);
3166	    if (lwlstr != NULL) free(lwlstr);
3167	#if	defined(SKF_RUBY19) || defined(SKF_RUBY2)
3168	    if (cstr != NULL) free(cstr);
3169	    return (ostrdef);
3170	#elif defined(SWIGPYTHON) && defined(SKF_PYTHON3)
3171	    ostrdef->sstr = (unsigned char *)skfobuf;
3172	    ostrdef->length = ostrdef->length;