bug#32338: 26.1; term.el broken on macOS

[Constantine Vetoshev <vetoshev@gmail.com>]

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On Sun, Sep 30, 2018 at 10:14 AM Eli Zaretskii <eliz@gnu.org> wrote:
> Then please step with a debugger through the code starting from the
> call to getrlimit, and please show the values of related variables,
> such as newlim, all the way until the call to setrlimit and the
> computed value of emacs_re_safe_alloca.  Please do that once with the
> current code and then once again with the code before the offending
> commit.  I'd like to see the differences, because I meanwhile see
> nothing wrong with using rlim_t here.

One change from my past reports: after compiling Emacs with -g flags,
I have now managed to reproduce the crash under lldb, including
attaching to the forked process which eats CPU after the crash.
Backtrace from that process is attached.

Here are my results from stepping through the code. Note this all runs
at Emacs startup, long before anything forks.

The highlights (as far as I noticed) are:
- emacs_re_max_failures and the older re_max_failures are not
initialized at this point
- in the working branch, newlim is reset to rlim.rlim_max; in the
broken branch, it is not
- in the working branch, setrlimit does not get called; in the broken
branch, it does

I'm guessing the problem is with the uninitialized values for
*_re_max_failures and the resulting values being assigned to lim and
newlim. It seems to only work on the working branch by accident
because, for whatever reason, newlim always gets reset to
rlim.rlim_max and setrlimit doesn't get called.

-----
master branch (commit 3eedabaef37e), use of rlim_t:

- immediately after getrlimit call, lim is assigned, value: 0
- lim is then assigned rlim.rlim_cur, value: 67104768
- min_ratio is initialized, value: 160
- ratio is initialized, value: 213
- try_to_grow_stack ends up assigned, value: true

The code proceeds into the try_to_grow_stack condition:

- newlim is assigned, value: 10020000
- BUT: emacs_re_max_failures defined at that point and used to
calculate newlim has a very large size_t value: 6500256977556508423
- looks like newlim has overflown here to fit unsigned long long
- pagesize is assigned, value 4096
- newlim is decremented, value: 10024095
- condition checking if rlim.rlim_max < newlim; rlim.rlim_max is
67104768 so the condition evaluates to false (emacs.c:880)
- condition checking if pagesize <= (newlim - lim) evaluates to true:
this happens because (newlim < rlim), and the subtraction causes an
overflow (newlim - lim returns an unsigned long long with value
18446744073652469760); consequently, setrlimit is called and succeeds

The try_to_grow_stack condition ends.

- emacs_re_safe_alloca is assigned, value: 4435280473597425792. I'm
not sure if that's a reasonable value for a value of type ptrdiff_t.
-----

-----
last working revision (commit 6cdd1c333034b), use of long:

Please note that this code predates the introduction of emacs_re_safe_alloca.

- immediately after getrlimit call, lim is assigned, value: 0
- lim then is assigned rlim.rlim_curr, value: 67104768
- ratio is then initialized: 160
- and subsequently incremented, value: 213
- try_to_grow_stack ends up assigned, value: true

The code proceeds into the try_to_grow_stack condition:

- newlim is assigned, value: 67104578
- BUT: re_max_failures defined at that point and used to calculate
newlim has a very large size_t value: 16107485546189635934
- newlim has obviously overflown here to fit a signed long
- pagesize is assigned, value 4096
- newlim is decremented, value: 67108673
- condition checking if rlim.rlim_max < newlim; rlim.rlim_max is
67104768 so the condition evaluates to true and newlim is set to
rlim.rlim_max (emacs.c:862)
- newlim decrement by newlim % pagesize is a noop
- condition checking if pagesize <= (newlim - lim) evaluates to false,
skipping the setrlimit call
-----

I am attaching lldb session transcripts for both runs in case you want
to look more closely at what's going on.

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(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
  * frame #0: 0x00007fff709835e2 libsystem_platform.dylib`_os_unfair_lock_recursive_abort + 23
    frame #1: 0x00007fff70983710 libsystem_platform.dylib`_os_unfair_lock_lock_slow + 226
    frame #2: 0x00007fff7081b2ee libsystem_malloc.dylib`szone_malloc_should_clear + 213
    frame #3: 0x00007fff7081b1bd libsystem_malloc.dylib`malloc_zone_malloc + 103
    frame #4: 0x00007fff487db6f4 CoreFoundation`CFBasicHashCreateCopy + 116
    frame #5: 0x00007fff487e3936 CoreFoundation`CFDictionaryCreateCopy + 134
    frame #6: 0x00007fff48982a28 CoreFoundation`__40-[_CFXPreferences synchronizeEverything]_block_invoke + 24
    frame #7: 0x00007fff4891b4cf CoreFoundation`-[_CFXPreferences(SourceAdditions) withSources:] + 79
    frame #8: 0x00007fff489829b3 CoreFoundation`-[_CFXPreferences synchronizeEverything] + 115
    frame #9: 0x00007fff4884cef9 CoreFoundation`_CFPrefsSynchronizeForProcessTermination + 73
    frame #10: 0x00007fff4a91df65 Foundation`-[NSUserDefaults(NSUserDefaults) synchronize] + 51
    frame #11: 0x0000000100335e72 Emacs`ns_term_shutdown(sig=4) at nsterm.m:5487
    frame #12: 0x000000010014edf4 Emacs`shut_down_emacs(sig=4, stuff=0x0000000000000000) at emacs.c:2136
    frame #13: 0x000000010014ea7f Emacs`terminate_due_to_signal(sig=4, backtrace_limit=40) at emacs.c:383
    frame #14: 0x0000000100182288 Emacs`handle_fatal_signal(sig=4) at sysdep.c:1769
    frame #15: 0x0000000100182322 Emacs`deliver_thread_signal(sig=4, handler=(Emacs`handle_fatal_signal at sysdep.c:1768)) at sysdep.c:1743
    frame #16: 0x00000001001800ea Emacs`deliver_fatal_thread_signal(sig=4) at sysdep.c:1781
    frame #17: 0x00007fff70980f5a libsystem_platform.dylib`_sigtramp + 26
    frame #18: 0x00007fff709835e3 libsystem_platform.dylib`_os_unfair_lock_recursive_abort + 24
    frame #19: 0x00007fff70983710 libsystem_platform.dylib`_os_unfair_lock_lock_slow + 226
    frame #20: 0x00007fff7081b7f2 libsystem_malloc.dylib`szone_malloc_should_clear + 1497
    frame #21: 0x00007fff7081b1bd libsystem_malloc.dylib`malloc_zone_malloc + 103
    frame #22: 0x00007fff7081a4c7 libsystem_malloc.dylib`malloc + 24
    frame #23: 0x00000001002b4fc2 Emacs`unexec_malloc(size=1024) at unexmacosx.c:1331
    frame #24: 0x00000001001f2555 Emacs`lmalloc(size=1024) at alloc.c:1461
    frame #25: 0x00000001001f24e5 Emacs`xmalloc(size=1024) at alloc.c:872
    frame #26: 0x00000001001e5064 Emacs`regex_compile(pattern="\\$\\(?:\\(?1:[[:alnum:]_]+\\)\\|{\\(?1:[^{}]+\\)}\\|\\$\\)", size=49, posix_backtracking=false, whitespace_regexp=0x0000000000000000, bufp=0x00000001007e05d8) at regex-emacs.c:1766
    frame #27: 0x00000001001e4f98 Emacs`rpl_re_compile_pattern(pattern="\\$\\(?:\\(?1:[[:alnum:]_]+\\)\\|{\\(?1:[^{}]+\\)}\\|\\$\\)", length=49, posix_backtracking=false, whitespace_regexp=0x0000000000000000, bufp=0x00000001007e05d8) at regex-emacs.c:5091
    frame #28: 0x00000001001d5c4c Emacs`compile_pattern_1(cp=0x00000001007e05b8, pattern=0x0000000100416f94, translate=0x000000010688786d, posix=false) at search.c:147
    frame #29: 0x00000001001cef70 Emacs`compile_pattern(pattern=0x0000000100416f94, regp=0x00000001007fa478, translate=0x000000010688786d, posix=false, multibyte=false) at search.c:258
    frame #30: 0x00000001001ce9c0 Emacs`string_match_1(regexp=0x0000000100416f94, string=0x000000010045b414, start=0x0000000000000002, posix=false) at search.c:419
    frame #31: 0x00000001001ce747 Emacs`Fstring_match(regexp=0x0000000100416f94, string=0x000000010045b414, start=0x0000000000000002) at search.c:466
    frame #32: 0x0000000100248ca8 Emacs`funcall_subr(subr=0x00000001003e00b8, numargs=3, args=0x00007ffeefbf8ad8) at eval.c:2936
    frame #33: 0x00000001002479fe Emacs`Ffuncall(nargs=4, args=0x00007ffeefbf8ad0) at eval.c:2856
    frame #34: 0x00000001002b997e Emacs`exec_byte_code(bytestr=0x0000000100416fe4, vector=0x0000000100417005, maxdepth=0x000000000000002a, args_template=0x0000000000000806, nargs=2, args=0x00007ffeefbf9208) at bytecode.c:632
    frame #35: 0x00000001002490dc Emacs`funcall_lambda(fun=0x0000000100416fb5, nargs=2, arg_vector=0x00007ffeefbf91f8) at eval.c:3057
    frame #36: 0x0000000100247a46 Emacs`Ffuncall(nargs=3, args=0x00007ffeefbf91f0) at eval.c:2858
    frame #37: 0x00000001002b997e Emacs`exec_byte_code(bytestr=0x00000001004170b4, vector=0x00000001004170d5, maxdepth=0x0000000000000016, args_template=0x0000000000000406, nargs=1, args=0x00007ffeefbf98b8) at bytecode.c:632
    frame #38: 0x00000001002490dc Emacs`funcall_lambda(fun=0x0000000100417085, nargs=1, arg_vector=0x00007ffeefbf98b0) at eval.c:3057
    frame #39: 0x0000000100247a46 Emacs`Ffuncall(nargs=2, args=0x00007ffeefbf98a8) at eval.c:2858
    frame #40: 0x0000000100248554 Emacs`call1(fn=0x000000000000b220, arg1=0x000000010045b414) at eval.c:2707
    frame #41: 0x00000001001af51c Emacs`Fsubstitute_in_file_name(filename=0x000000010045b414) at fileio.c:1763
    frame #42: 0x000000010028b3e4 Emacs`Fload(file=0x000000010045b414, noerror=0x0000000000000000, nomessage=0x000000000000b460, nosuffix=0x0000000000000000, must_suffix=0x000000000000b460) at lread.c:1175
    frame #43: 0x000000010023fca6 Emacs`Fautoload_do_load(fundef=0x000000010045b3f3, funname=0x0000000000003ea0, macro_only=0x0000000000000000) at eval.c:2109
    frame #44: 0x0000000100247b90 Emacs`Ffuncall(nargs=3, args=0x00007ffeefbf9fd0) at eval.c:2873
    frame #45: 0x00000001002477ca Emacs`Fapply(nargs=2, args=0x00007ffeefbfa0d8) at eval.c:2476
    frame #46: 0x0000000100239305 Emacs`apply1(fn=0x0000000000003ea0, arg=0x00000001038c9d53) at eval.c:2692
    frame #47: 0x0000000100238cdf Emacs`call_debugger(arg=0x00000001038c9d53) at eval.c:358
    frame #48: 0x0000000100247c1a Emacs`Ffuncall(nargs=8, args=0x00007ffeefbfa470) at eval.c:2883

[-- Attachment #3: lldb-session-working.txt --]
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(lldb) target create "nextstep/Emacs.app/Contents/MacOS/Emacs"
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/opt/brew/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy.py", line 52, in <module>
    import weakref
  File "/opt/brew/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/weakref.py", line 14, in <module>
    from _weakref import (
ImportError: cannot import name _remove_dead_weakref
Current executable set to 'nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64).
(lldb) b emacs.c:832
Breakpoint 1: where = Emacs`main + 1463 at emacs.c:832, address = 0x0000000100133ef7
(lldb) run -Q
Process 96113 launched: '/Users/kostya/Downloads/emacs-working.git/nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64)
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100133ef7 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:832
   829    if (getrlimit (RLIMIT_STACK, &rlim) == 0
   830        && 0 <= rlim.rlim_cur && rlim.rlim_cur <= LONG_MAX)
   831      {
-> 832        long lim = rlim.rlim_cur;
   833
   834        /* Approximate the amount regex.c needs per unit of
   835           re_max_failures, then add 33% to cover the size of the
Target 0: (Emacs) stopped.
(lldb) e lim
(long) $0 = 0
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f05 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:838
   835           re_max_failures, then add 33% to cover the size of the
   836           smaller stacks that regex.c successively allocates and
   837           discards on its way to the maximum.  */
-> 838        int ratio = 20 * sizeof (char *);
   839        ratio += ratio / 3;
   840
   841        /* Extra space to cover what we're likely to use for other reasons.  */
Target 0: (Emacs) stopped.
(lldb) e lim
(long) $1 = 67104768
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f0f Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:839
   836           smaller stacks that regex.c successively allocates and
   837           discards on its way to the maximum.  */
   838        int ratio = 20 * sizeof (char *);
-> 839        ratio += ratio / 3;
   840
   841        /* Extra space to cover what we're likely to use for other reasons.  */
   842        int extra = 200000;
Target 0: (Emacs) stopped.
(lldb) e ratio
(int) $2 = 160
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f38 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:842
   839        ratio += ratio / 3;
   840
   841        /* Extra space to cover what we're likely to use for other reasons.  */
-> 842        int extra = 200000;
   843
   844        bool try_to_grow_stack = true;
   845  #ifndef CANNOT_DUMP
Target 0: (Emacs) stopped.
(lldb) e ratio
(int) $3 = 213
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f42 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:844
   841        /* Extra space to cover what we're likely to use for other reasons.  */
   842        int extra = 200000;
   843
-> 844        bool try_to_grow_stack = true;
   845  #ifndef CANNOT_DUMP
   846        try_to_grow_stack = !noninteractive || initialized;
   847  #endif
Target 0: (Emacs) stopped.
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f49 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:846
   843
   844        bool try_to_grow_stack = true;
   845  #ifndef CANNOT_DUMP
-> 846        try_to_grow_stack = !noninteractive || initialized;
   847  #endif
   848
   849        if (try_to_grow_stack)
Target 0: (Emacs) stopped.
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f7d Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:849
   846        try_to_grow_stack = !noninteractive || initialized;
   847  #endif
   848
-> 849        if (try_to_grow_stack)
   850          {
   851            long newlim = re_max_failures * ratio + extra;
   852
Target 0: (Emacs) stopped.
(lldb) e try_to_grow_stack
(bool) $4 = true
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133f91 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:851
   848
   849        if (try_to_grow_stack)
   850          {
-> 851            long newlim = re_max_failures * ratio + extra;
   852
   853            /* Round the new limit to a page boundary; this is needed
   854               for Darwin kernel 15.4.0 (see Bug#23622) and perhaps
Target 0: (Emacs) stopped.
(lldb) e newlim
(long) $5 = 0
(lldb) e re_max_failures
(size_t) $6 = 16107485546189635934
(lldb) e extra
(int) $7 = 200000
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133fb0 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:860
   857               RLIM_INFINITY etc. since in practice when they are
   858               nonnegative they are so large that the code does the
   859               right thing anyway.  */
-> 860            long pagesize = getpagesize ();
   861            newlim += pagesize - 1;
   862            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   863              newlim = rlim.rlim_max;
Target 0: (Emacs) stopped.
(lldb) e newlim
(long) $8 = 67104578
(lldb) e re_max_failures
(size_t) $9 = 16107485546189635934
(lldb) e ratio
(int) $10 = 213
(lldb) e re_max_failures * ratio
(unsigned long) $11 = 18246767702125404982
(lldb) e re_max_failures * ratio + extra
(unsigned long) $12 = 18246767702125604982
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133fc3 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:861
   858               nonnegative they are so large that the code does the
   859               right thing anyway.  */
   860            long pagesize = getpagesize ();
-> 861            newlim += pagesize - 1;
   862            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   863              newlim = rlim.rlim_max;
   864            newlim -= newlim % pagesize;
Target 0: (Emacs) stopped.
(lldb) e pagesize
(long) $13 = 4096
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133fdc Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:862
   859               right thing anyway.  */
   860            long pagesize = getpagesize ();
   861            newlim += pagesize - 1;
-> 862            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   863              newlim = rlim.rlim_max;
   864            newlim -= newlim % pagesize;
   865
Target 0: (Emacs) stopped.
(lldb) e newlim
(long) $14 = 67108673
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100133ffd Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:863
   860            long pagesize = getpagesize ();
   861            newlim += pagesize - 1;
   862            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
-> 863              newlim = rlim.rlim_max;
   864            newlim -= newlim % pagesize;
   865
   866            if (pagesize <= newlim - lim)
Target 0: (Emacs) stopped.
(lldb) e rlim.rlim_max
(rlim_t) $15 = 67104768
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010013400b Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:864
   861            newlim += pagesize - 1;
   862            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   863              newlim = rlim.rlim_max;
-> 864            newlim -= newlim % pagesize;
   865
   866            if (pagesize <= newlim - lim)
   867              {
Target 0: (Emacs) stopped.
(lldb) e newlim
(long) $16 = 67104768
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010013402c Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:866
   863              newlim = rlim.rlim_max;
   864            newlim -= newlim % pagesize;
   865
-> 866            if (pagesize <= newlim - lim)
   867              {
   868                rlim.rlim_cur = newlim;
   869                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
Target 0: (Emacs) stopped.
(lldb) e newlim
(long) $17 = 67104768
(lldb) e newlim % pagesize
(long) $18 = 0
(lldb) e pagesize
(long) $19 = 4096
(lldb) e newlim - lim
(long) $20 = 0
(lldb) n
Process 96113 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100134085 Emacs`main(argc=2, argv=0x00007ffeefbff520) at emacs.c:872
   869                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
   870                  lim = newlim;
   871              }
-> 872          }
   873
   874        /* Don't let regex.c overflow the stack.  */
   875        re_max_failures = lim < extra ? 0 : min (lim - extra, SIZE_MAX) / ratio;
Target 0: (Emacs) stopped.
(lldb) c
Process 96113 resuming
2018-10-02 14:11:54.227006-0700 Emacs[96113:1856908] MessageTracer: Falling back to default whitelist
2018-10-02 14:11:54.331905-0700 Emacs[96113:1900949] flock failed to lock maps file: errno = 35
2018-10-02 14:11:54.332259-0700 Emacs[96113:1900949] flock failed to lock maps file: errno = 35
Process 96113 exited with status = 0 (0x00000000)

[-- Attachment #4: lldb-session-broken.txt --]
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(lldb) target create "nextstep/Emacs.app/Contents/MacOS/Emacs"
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/opt/brew/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy.py", line 52, in <module>
    import weakref
  File "/opt/brew/Cellar/python@2/2.7.15_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/weakref.py", line 14, in <module>
    from _weakref import (
ImportError: cannot import name _remove_dead_weakref
Current executable set to 'nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64).
(lldb) b emacs.c:848
Breakpoint 1: where = Emacs`main + 1489 at emacs.c:848, address = 0x000000010014f431
(lldb) run -Q
Process 97130 launched: '/Users/kostya/Downloads/emacs-master.git/nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64)
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x000000010014f431 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:848
   845    if (getrlimit (RLIMIT_STACK, &rlim) == 0
   846        && 0 <= rlim.rlim_cur && rlim.rlim_cur <= LONG_MAX)
   847      {
-> 848        rlim_t lim = rlim.rlim_cur;
   849
   850        /* Approximate the amount regex-emacs.c needs per unit of
   851           emacs_re_max_failures, then add 33% to cover the size of the
Target 0: (Emacs) stopped.
(lldb) e lim
(rlim_t) $0 = 0
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f43f Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:854
   851           emacs_re_max_failures, then add 33% to cover the size of the
   852           smaller stacks that regex-emacs.c successively allocates and
   853           discards on its way to the maximum.  */
-> 854        int min_ratio = 20 * sizeof (char *);
   855        int ratio = min_ratio + min_ratio / 3;
   856
   857        /* Extra space to cover what we're likely to use for other
Target 0: (Emacs) stopped.
(lldb) e lim
(rlim_t) $1 = 67104768
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f449 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:855
   852           smaller stacks that regex-emacs.c successively allocates and
   853           discards on its way to the maximum.  */
   854        int min_ratio = 20 * sizeof (char *);
-> 855        int ratio = min_ratio + min_ratio / 3;
   856
   857        /* Extra space to cover what we're likely to use for other
   858           reasons.  For example, a typical GC might take 30K stack
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f478 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:860
   857        /* Extra space to cover what we're likely to use for other
   858           reasons.  For example, a typical GC might take 30K stack
   859           frames.  */
-> 860        int extra = (30 * 1000) * 50;
   861
   862        bool try_to_grow_stack = true;
   863  #ifndef CANNOT_DUMP
Target 0: (Emacs) stopped.
(lldb) e min_ratio
(int) $2 = 160
(lldb) e ratio
(int) $3 = 213
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f482 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:862
   859           frames.  */
   860        int extra = (30 * 1000) * 50;
   861
-> 862        bool try_to_grow_stack = true;
   863  #ifndef CANNOT_DUMP
   864        try_to_grow_stack = !noninteractive || initialized;
   865  #endif
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f489 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:864
   861
   862        bool try_to_grow_stack = true;
   863  #ifndef CANNOT_DUMP
-> 864        try_to_grow_stack = !noninteractive || initialized;
   865  #endif
   866
   867        if (try_to_grow_stack)
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f4bd Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:867
   864        try_to_grow_stack = !noninteractive || initialized;
   865  #endif
   866
-> 867        if (try_to_grow_stack)
   868          {
   869            rlim_t newlim = emacs_re_max_failures * ratio + extra;
   870
Target 0: (Emacs) stopped.
(lldb) e try_to_grow_stack
(bool) $4 = true
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f4d1 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:869
   866
   867        if (try_to_grow_stack)
   868          {
-> 869            rlim_t newlim = emacs_re_max_failures * ratio + extra;
   870
   871            /* Round the new limit to a page boundary; this is needed
   872               for Darwin kernel 15.4.0 (see Bug#23622) and perhaps
Target 0: (Emacs) stopped.
(lldb) e emacs_re_max_failures
(size_t) $5 = 6500256977556508423
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f4f0 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:878
   875               RLIM_INFINITY etc. since in practice when they are
   876               nonnegative they are so large that the code does the
   877               right thing anyway.  */
-> 878            long pagesize = getpagesize ();
   879            newlim += pagesize - 1;
   880            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   881              newlim = rlim.rlim_max;
Target 0: (Emacs) stopped.
(lldb) e newlim
(rlim_t) $6 = 10020000
(lldb) e emacs_re_max_failures
(size_t) $7 = 6500256977556508423
(lldb) e ratio
(int) $8 = 213
(lldb) e emacs_re_max_failures * ratio
(unsigned long) $9 = 1048930691319922899
(lldb) e emacs_re_max_failures * ratio + extra
(unsigned long) $10 = 1048930691321422899
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f503 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:879
   876               nonnegative they are so large that the code does the
   877               right thing anyway.  */
   878            long pagesize = getpagesize ();
-> 879            newlim += pagesize - 1;
   880            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   881              newlim = rlim.rlim_max;
   882            newlim -= newlim % pagesize;
Target 0: (Emacs) stopped.
(lldb) e pagesize
(long) $11 = 4096
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f51c Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:880
   877               right thing anyway.  */
   878            long pagesize = getpagesize ();
   879            newlim += pagesize - 1;
-> 880            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   881              newlim = rlim.rlim_max;
   882            newlim -= newlim % pagesize;
   883
Target 0: (Emacs) stopped.
(lldb) e newlim
(rlim_t) $12 = 10024095
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f54b Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:882
   879            newlim += pagesize - 1;
   880            if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
   881              newlim = rlim.rlim_max;
-> 882            newlim -= newlim % pagesize;
   883
   884            if (pagesize <= newlim - lim)
   885              {
Target 0: (Emacs) stopped.
(lldb) e rlim.rlim_max
(rlim_t) $13 = 67104768
(lldb) e newlim
(rlim_t) $14 = 10024095
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f56e Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:884
   881              newlim = rlim.rlim_max;
   882            newlim -= newlim % pagesize;
   883
-> 884            if (pagesize <= newlim - lim)
   885              {
   886                rlim.rlim_cur = newlim;
   887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
Target 0: (Emacs) stopped.
(lldb) e newlim
(rlim_t) $15 = 10022912
(lldb) e newlim - lim
(unsigned long long) $16 = 18446744073652469760
(lldb) e lim
(rlim_t) $17 = 67104768
(lldb) e newlim
(rlim_t) $18 = 10022912
(lldb) e pagesize
(long) $19 = 4096
(lldb) e newlim
(rlim_t) $20 = 10022912
(lldb) e lim
(rlim_t) $21 = 67104768
(lldb) e newlim - lim
(unsigned long long) $22 = 18446744073652469760
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f598 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:886
   883
   884            if (pagesize <= newlim - lim)
   885              {
-> 886                rlim.rlim_cur = newlim;
   887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
   888                  lim = newlim;
   889              }
Target 0: (Emacs) stopped.
(lldb) e newlim
(rlim_t) $23 = 10022912
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f5a6 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:887
   884            if (pagesize <= newlim - lim)
   885              {
   886                rlim.rlim_cur = newlim;
-> 887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
   888                  lim = newlim;
   889              }
   890          }
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f5b4 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:888
   885              {
   886                rlim.rlim_cur = newlim;
   887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
-> 888                  lim = newlim;
   889              }
   890          }
   891        /* If the stack is big enough, let regex-emacs.c more of it before
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f5c2 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:889
   886                rlim.rlim_cur = newlim;
   887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
   888                  lim = newlim;
-> 889              }
   890          }
   891        /* If the stack is big enough, let regex-emacs.c more of it before
   892           falling back to heap allocation.  */
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f5c7 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:890
   887                if (setrlimit (RLIMIT_STACK, &rlim) == 0)
   888                  lim = newlim;
   889              }
-> 890          }
   891        /* If the stack is big enough, let regex-emacs.c more of it before
   892           falling back to heap allocation.  */
   893        emacs_re_safe_alloca = max
Target 0: (Emacs) stopped.
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f5cc Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:893
   890          }
   891        /* If the stack is big enough, let regex-emacs.c more of it before
   892           falling back to heap allocation.  */
-> 893        emacs_re_safe_alloca = max
   894          (min (lim - extra, SIZE_MAX) * (min_ratio / ratio),
   895           MAX_ALLOCA);
   896      }
Target 0: (Emacs) stopped.
(lldb) e emacs_re_safe_alloca
(ptrdiff_t) $24 = 4435280473597425792
(lldb) n
Process 97130 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010014f701 Emacs`main(argc=2, argv=0x00007ffeefbff518) at emacs.c:899
   896      }
   897  #endif /* HAVE_SETRLIMIT and RLIMIT_STACK and not CYGWIN */
   898
-> 899    clearerr_unlocked (stdin);
   900
   901    emacs_backtrace (-1);
   902
Target 0: (Emacs) stopped.
(lldb) e emacs_re_safe_alloca
(ptrdiff_t) $25 = 4435280473597425792
(lldb) c
Process 97130 resuming
2018-10-02 15:38:55.115287-0700 Emacs[97130:1949757] MessageTracer: Falling back to default whitelist
2018-10-02 15:38:55.225413-0700 Emacs[97130:2016511] flock failed to lock maps file: errno = 35
2018-10-02 15:38:55.227137-0700 Emacs[97130:2016511] flock failed to lock maps file: errno = 35
Process 97130 exited with status = 0 (0x00000000)