-

% lldb -- ./miniruby -e0
(lldb) target create "./miniruby"
Current executable set to './miniruby' (x86_64).
(lldb) settings set -- target.run-args  "-e0"
(lldb) env DYLD_INSERT_LIBRARIES=/usr/lib/libgmalloc.dylib
(lldb) env MALLOC_CHECK_HARDER=1
(lldb) env MALLOC_PROTECT_BEFORE=1
(lldb) env RUBY_DEBUG=gc_stress
(lldb) run
Process 11348 launched: './miniruby' (x86_64)
GuardMalloc[miniruby-11348]: Allocations will be placed on 16 byte boundaries.
GuardMalloc[miniruby-11348]:  - Some buffer overruns may not be noticed.
GuardMalloc[miniruby-11348]:  - Applications using vector instructions (e.g., SSE) should work.
GuardMalloc[miniruby-11348]: version 108
Process 11348 stopped
* thread #1: tid = 0x80594, 0x00000001000877c9 miniruby`gc_sweep_step(objspace=0x0000000100cab000, heap=0x0000000100cab020) + 409 at gc.c:3371, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x100ecc010)
    frame #0: 0x00000001000877c9 miniruby`gc_sweep_step(objspace=0x0000000100cab000, heap=0x0000000100cab020) + 409 at gc.c:3371
   3368             p = offset  + i * BITS_BITLENGTH;
   3369             do {
   3370                 if (bitset & 1) {
-> 3371                     switch (BUILTIN_TYPE(p)) {
   3372                       default: { /* majority case */
   3373                           gc_report(2, objspace, "page_sweep: free %s\n", obj_info((VALUE)p));
   3374 #if USE_RGENGC && RGENGC_CHECK_MODE
(lldb) bt
* thread #1: tid = 0x80594, 0x00000001000877c9 miniruby`gc_sweep_step(objspace=0x0000000100cab000, heap=0x0000000100cab020) + 409 at gc.c:3371, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x100ecc010)
  * frame #0: 0x00000001000877c9 miniruby`gc_sweep_step(objspace=0x0000000100cab000, heap=0x0000000100cab020) + 409 at gc.c:3371
    frame #1: 0x00000001000861db miniruby`gc_sweep + 20 at gc.c:3608
    frame #2: 0x00000001000861c7 miniruby`gc_sweep(objspace=0x0000000100cab000) + 311
    frame #3: 0x0000000100086d5c miniruby`gc_start(objspace=0x0000000100cab000, full_mark=<unavailable>, immediate_mark=<unavailable>, reason=<unavailable>, immediate_sweep=<unavailable>) + 1724 at gc.c:5457
    frame #4: 0x0000000100087293 miniruby`garbage_collect_with_gvl(objspace=0x0000000100cab000, full_mark=0, immediate_mark=1, immediate_sweep=1, reason=4608) + 131 at gc.c:6394
    frame #5: 0x0000000100089bd8 miniruby`objspace_xmalloc [inlined] objspace_malloc_gc_stress(objspace=0x0000000100cab000) + 152 at gc.c:7531
    frame #6: 0x0000000100089ba9 miniruby`objspace_xmalloc [inlined] objspace_malloc_gc_stress(objspace=<unavailable>)
    frame #7: 0x0000000100089ba9 miniruby`objspace_xmalloc(objspace=0x0000000100cab000, size=<unavailable>) + 105
    frame #8: 0x000000010015d3eb miniruby`st_init_numtable + 10 at st.c:222
    frame #9: 0x000000010015d3e1 miniruby`st_init_numtable [inlined] st_init_table(type=<unavailable>)
    frame #10: 0x000000010015d3e1 miniruby`st_init_numtable + 1
    frame #11: 0x000000010008a291 miniruby`Init_heap + 481 at gc.c:2269
    frame #12: 0x0000000100062ecb miniruby`ruby_setup + 43 at eval.c:55
    frame #13: 0x0000000100062f89 miniruby`ruby_init + 9 at eval.c:76
    frame #14: 0x000000010020fe5d miniruby`main(argc=<unavailable>, argv=<unavailable>) + 77 at main.c:35
    frame #15: 0x00007fff972a35ad libdyld.dylib`start + 1
    frame #16: 0x00007fff972a35ad libdyld.dylib`start + 1
(lldb)