Ruby 2.4.1 has "Stack consistency error" and aborts when processing return statement within a case statement

Hi, I found the following file causes a ruby bug stating "Stack consistency error" and aborts. File: ``` 0>case when 0 return end ``` xxd -g1 output of file ``` 00000000: 30 3e 63 61 73 65 0a 77 68 65 6e 20 30 0a 72 65 0>case.when 0.re 00000010: 74 75 72 6e 20 65 6e 64 0a turn end. ``` ruby output: ``` crash.rb:3: [BUG] Stack consistency error (sp: 7, bp: 6) ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux] -- Control frame information ----------------------------------------------- c:0002 p:0011 s:0007 e:000005 EVAL crash.rb:3 [FINISH] c:0001 p:0000 s:0003 E:0005d0 (none) [FINISH] -- Ruby level backtrace information ---------------------------------------- crash.rb:3:in `<main>' -- Other runtime information ----------------------------------------------- * Loaded script: crash.rb * Loaded features: 0 enumerator.so 1 thread.rb 2 rational.so 3 complex.so 4 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/encdb.so 5 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/trans/transdb.so 6 /usr/local/lib/ruby/2.4.0/unicode_normalize.rb 7 /usr/local/lib/ruby/2.4.0/x86_64-linux/rbconfig.rb 8 /usr/local/lib/ruby/2.4.0/rubygems/compatibility.rb 9 /usr/local/lib/ruby/2.4.0/rubygems/defaults.rb 10 /usr/local/lib/ruby/2.4.0/rubygems/deprecate.rb 11 /usr/local/lib/ruby/2.4.0/rubygems/errors.rb 12 /usr/local/lib/ruby/2.4.0/rubygems/version.rb 13 /usr/local/lib/ruby/2.4.0/rubygems/requirement.rb 14 /usr/local/lib/ruby/2.4.0/rubygems/platform.rb 15 /usr/local/lib/ruby/2.4.0/rubygems/basic_specification.rb 16 /usr/local/lib/ruby/2.4.0/rubygems/stub_specification.rb 17 /usr/local/lib/ruby/2.4.0/rubygems/util/list.rb 18 /usr/local/lib/ruby/2.4.0/x86_64-linux/stringio.so 19 /usr/local/lib/ruby/2.4.0/rubygems/specification.rb 20 /usr/local/lib/ruby/2.4.0/rubygems/exceptions.rb 21 /usr/local/lib/ruby/2.4.0/rubygems/dependency.rb 22 /usr/local/lib/ruby/2.4.0/rubygems/core_ext/kernel_gem.rb 23 /usr/local/lib/ruby/2.4.0/monitor.rb 24 /usr/local/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb 25 /usr/local/lib/ruby/2.4.0/rubygems.rb 26 /usr/local/lib/ruby/2.4.0/rubygems/path_support.rb 27 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/version.rb 28 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/core_ext/name_error.rb 29 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/levenshtein.rb 30 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/jaro_winkler.rb 31 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checker.rb 32 /usr/local/lib/ruby/2.4.0/delegate.rb 33 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checkers/name_error_checkers/class_name_checker.rb 34 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checkers/name_error_checkers/variable_name_checker.rb 35 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checkers/name_error_checkers.rb 36 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checkers/method_name_checker.rb 37 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/spell_checkers/null_checker.rb 38 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean/formatter.rb 39 /usr/local/lib/ruby/gems/2.4.0/gems/did_you_mean-1.1.0/lib/did_you_mean.rb * Process memory map: 7fff7000-8fff7000 rw-p 00000000 00:00 0 8fff7000-2008fff7000 ---p 00000000 00:00 0 2008fff7000-10007fff8000 rw-p 00000000 00:00 0 562660459000-562660f58000 r-xp 00000000 fd:01 135 /usr/local/bin/ruby 562661158000-56266117e000 r--p 00aff000 fd:01 135 /usr/local/bin/ruby 56266117e000-5626611ed000 rw-p 00b25000 fd:01 135 /usr/local/bin/ruby 5626611ed000-562661e89000 rw-p 00000000 00:00 0 600000000000-602000000000 ---p 00000000 00:00 0 602000000000-602000020000 rw-p 00000000 00:00 0 602000020000-603000000000 ---p 00000000 00:00 0 603000000000-603000060000 rw-p 00000000 00:00 0 603000060000-604000000000 ---p 00000000 00:00 0 604000000000-604000080000 rw-p 00000000 00:00 0 604000080000-606000000000 ---p 00000000 00:00 0 606000000000-606000090000 rw-p 00000000 00:00 0 606000090000-607000000000 ---p 00000000 00:00 0 607000000000-607000080000 rw-p 00000000 00:00 0 607000080000-608000000000 ---p 00000000 00:00 0 608000000000-608000050000 rw-p 00000000 00:00 0 608000050000-60b000000000 ---p 00000000 00:00 0 60b000000000-60b000020000 rw-p 00000000 00:00 0 60b000020000-60c000000000 ---p 00000000 00:00 0 60c000000000-60c000040000 rw-p 00000000 00:00 0 60c000040000-60d000000000 ---p 00000000 00:00 0 60d000000000-60d000050000 rw-p 00000000 00:00 0 60d000050000-60e000000000 ---p 00000000 00:00 0 60e000000000-60e000030000 rw-p 00000000 00:00 0 60e000030000-60f000000000 ---p 00000000 00:00 0 60f000000000-60f000010000 rw-p 00000000 00:00 0 60f000010000-610000000000 ---p 00000000 00:00 0 610000000000-610000020000 rw-p 00000000 00:00 0 610000020000-611000000000 ---p 00000000 00:00 0 611000000000-611000080000 rw-p 00000000 00:00 0 611000080000-612000000000 ---p 00000000 00:00 0 612000000000-612000030000 rw-p 00000000 00:00 0 612000030000-613000000000 ---p 00000000 00:00 0 613000000000-613000020000 rw-p 00000000 00:00 0 613000020000-614000000000 ---p 00000000 00:00 0 614000000000-614000030000 rw-p 00000000 00:00 0 614000030000-615000000000 ---p 00000000 00:00 0 615000000000-615000020000 rw-p 00000000 00:00 0 615000020000-616000000000 ---p 00000000 00:00 0 616000000000-616000360000 rw-p 00000000 00:00 0 616000360000-617000000000 ---p 00000000 00:00 0 617000000000-617000030000 rw-p 00000000 00:00 0 617000030000-618000000000 ---p 00000000 00:00 0 618000000000-618000020000 rw-p 00000000 00:00 0 618000020000-619000000000 ---p 00000000 00:00 0 619000000000-619000050000 rw-p 00000000 00:00 0 619000050000-61a000000000 ---p 00000000 00:00 0 61a000000000-61a000020000 rw-p 00000000 00:00 0 61a000020000-61b000000000 ---p 00000000 00:00 0 61b000000000-61b000020000 rw-p 00000000 00:00 0 61b000020000-61c000000000 ---p 00000000 00:00 0 61c000000000-61c000020000 rw-p 00000000 00:00 0 61c000020000-61d000000000 ---p 00000000 00:00 0 61d000000000-61d000020000 rw-p 00000000 00:00 0 61d000020000-61e000000000 ---p 00000000 00:00 0 61e000000000-61e000020000 rw-p 00000000 00:00 0 61e000020000-61f000000000 ---p 00000000 00:00 0 61f000000000-61f000030000 rw-p 00000000 00:00 0 61f000030000-620000000000 ---p 00000000 00:00 0 620000000000-620000020000 rw-p 00000000 00:00 0 620000020000-621000000000 ---p 00000000 00:00 0 621000000000-621000080000 rw-p 00000000 00:00 0 621000080000-622000000000 ---p 00000000 00:00 0 622000000000-622000020000 rw-p 00000000 00:00 0 622000020000-623000000000 ---p 00000000 00:00 0 623000000000-623000030000 rw-p 00000000 00:00 0 623000030000-624000000000 ---p 00000000 00:00 0 624000000000-624000060000 rw-p 00000000 00:00 0 624000060000-625000000000 ---p 00000000 00:00 0 625000000000-625000090000 rw-p 00000000 00:00 0 625000090000-626000000000 ---p 00000000 00:00 0 626000000000-626000030000 rw-p 00000000 00:00 0 626000030000-627000000000 ---p 00000000 00:00 0 627000000000-627000020000 rw-p 00000000 00:00 0 627000020000-628000000000 ---p 00000000 00:00 0 628000000000-628000010000 rw-p 00000000 00:00 0 628000010000-629000000000 ---p 00000000 00:00 0 629000000000-629000020000 rw-p 00000000 00:00 0 629000020000-62b000000000 ---p 00000000 00:00 0 62b000000000-62b000030000 rw-p 00000000 00:00 0 62b000030000-62c000000000 ---p 00000000 00:00 0 62c000000000-62c000020000 rw-p 00000000 00:00 0 62c000020000-62d000000000 ---p 00000000 00:00 0 62d000000000-62d0002d0000 rw-p 00000000 00:00 0 62d0002d0000-62f000000000 ---p 00000000 00:00 0 62f000000000-62f000030000 rw-p 00000000 00:00 0 62f000030000-632000000000 ---p 00000000 00:00 0 632000000000-632000030000 rw-p 00000000 00:00 0 632000030000-633000000000 ---p 00000000 00:00 0 633000000000-633000060000 rw-p 00000000 00:00 0 633000060000-640000000000 ---p 00000000 00:00 0 640000000000-640000003000 rw-p 00000000 00:00 0 7fb057651000-7fb057683000 rw-p 00000000 00:00 0 7fb057683000-7fb05769e000 r-xp 00000000 fd:01 513782 /usr/local/lib/ruby/2.4.0/x86_64-linux/stringio.so 7fb05769e000-7fb05789e000 ---p 0001b000 fd:01 513782 /usr/local/lib/ruby/2.4.0/x86_64-linux/stringio.so 7fb05789e000-7fb05789f000 r--p 0001b000 fd:01 513782 /usr/local/lib/ruby/2.4.0/x86_64-linux/stringio.so 7fb05789f000-7fb0578a1000 rw-p 0001c000 fd:01 513782 /usr/local/lib/ruby/2.4.0/x86_64-linux/stringio.so 7fb0578a1000-7fb0578a9000 r-xp 00000000 fd:01 768982 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/trans/transdb.so 7fb0578a9000-7fb057aa8000 ---p 00008000 fd:01 768982 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/trans/transdb.so 7fb057aa8000-7fb057aa9000 r--p 00007000 fd:01 768982 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/trans/transdb.so 7fb057aa9000-7fb057aab000 rw-p 00008000 fd:01 768982 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/trans/transdb.so 7fb057aab000-7fb057ab5000 r-xp 00000000 fd:01 768950 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/encdb.so 7fb057ab5000-7fb057cb4000 ---p 0000a000 fd:01 768950 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/encdb.so 7fb057cb4000-7fb057cb5000 r--p 00009000 fd:01 768950 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/encdb.so 7fb057cb5000-7fb057cb8000 rw-p 0000a000 fd:01 768950 /usr/local/lib/ruby/2.4.0/x86_64-linux/enc/encdb.so 7fb057cb8000-7fb057e50000 r--p 00000000 fd:01 5196 /usr/lib/locale/locale-archive 7fb057e50000-7fb05a1a2000 rw-p 00000000 00:00 0 7fb05a1a2000-7fb05a362000 r-xp 00000000 fd:01 12855 /lib/x86_64-linux-gnu/libc-2.23.so 7fb05a362000-7fb05a562000 ---p 001c0000 fd:01 12855 /lib/x86_64-linux-gnu/libc-2.23.so 7fb05a562000-7fb05a566000 r--p 001c0000 fd:01 12855 /lib/x86_64-linux-gnu/libc-2.23.so 7fb05a566000-7fb05a568000 rw-p 001c4000 fd:01 12855 /lib/x86_64-linux-gnu/libc-2.23.so 7fb05a568000-7fb05a56c000 rw-p 00000000 00:00 0 7fb05a56c000-7fb05a582000 r-xp 00000000 fd:01 2035 /lib/x86_64-linux-gnu/libgcc_s.so.1 7fb05a582000-7fb05a781000 ---p 00016000 fd:01 2035 /lib/x86_64-linux-gnu/libgcc_s.so.1 7fb05a781000-7fb05a782000 rw-p 00015000 fd:01 2035 /lib/x86_64-linux-gnu/libgcc_s.so.1 7fb05a782000-7fb05a789000 r-xp 00000000 fd:01 12841 /lib/x86_64-linux-gnu/librt-2.23.so 7fb05a789000-7fb05a988000 ---p 00007000 fd:01 12841 /lib/x86_64-linux-gnu/librt-2.23.so 7fb05a988000-7fb05a989000 r--p 00006000 fd:01 12841 /lib/x86_64-linux-gnu/librt-2.23.so 7fb05a989000-7fb05a98a000 rw-p 00007000 fd:01 12841 /lib/x86_64-linux-gnu/librt-2.23.so 7fb05a98a000-7fb05aa92000 r-xp 00000000 fd:01 12850 /lib/x86_64-linux-gnu/libm-2.23.so 7fb05aa92000-7fb05ac91000 ---p 00108000 fd:01 12850 /lib/x86_64-linux-gnu/libm-2.23.so 7fb05ac91000-7fb05ac92000 r--p 00107000 fd:01 12850 /lib/x86_64-linux-gnu/libm-2.23.so 7fb05ac92000-7fb05ac93000 rw-p 00108000 fd:01 12850 /lib/x86_64-linux-gnu/libm-2.23.so 7fb05ac93000-7fb05ac9c000 r-xp 00000000 fd:01 12837 /lib/x86_64-linux-gnu/libcrypt-2.23.so 7fb05ac9c000-7fb05ae9b000 ---p 00009000 fd:01 12837 /lib/x86_64-linux-gnu/libcrypt-2.23.so 7fb05ae9b000-7fb05ae9c000 r--p 00008000 fd:01 12837 /lib/x86_64-linux-gnu/libcrypt-2.23.so 7fb05ae9c000-7fb05ae9d000 rw-p 00009000 fd:01 12837 /lib/x86_64-linux-gnu/libcrypt-2.23.so 7fb05ae9d000-7fb05aecb000 rw-p 00000000 00:00 0 7fb05aecb000-7fb05aece000 r-xp 00000000 fd:01 12844 /lib/x86_64-linux-gnu/libdl-2.23.so 7fb05aece000-7fb05b0cd000 ---p 00003000 fd:01 12844 /lib/x86_64-linux-gnu/libdl-2.23.so 7fb05b0cd000-7fb05b0ce000 r--p 00002000 fd:01 12844 /lib/x86_64-linux-gnu/libdl-2.23.so 7fb05b0ce000-7fb05b0cf000 rw-p 00003000 fd:01 12844 /lib/x86_64-linux-gnu/libdl-2.23.so 7fb05b0cf000-7fb05b14e000 r-xp 00000000 fd:01 25776 /usr/lib/x86_64-linux-gnu/libgmp.so.10.3.0 7fb05b14e000-7fb05b34d000 ---p 0007f000 fd:01 25776 /usr/lib/x86_64-linux-gnu/libgmp.so.10.3.0 7fb05b34d000-7fb05b34e000 r--p 0007e000 fd:01 25776 /usr/lib/x86_64-linux-gnu/libgmp.so.10.3.0 7fb05b34e000-7fb05b34f000 rw-p 0007f000 fd:01 25776 /usr/lib/x86_64-linux-gnu/libgmp.so.10.3.0 7fb05b34f000-7fb05b367000 r-xp 00000000 fd:01 12838 /lib/x86_64-linux-gnu/libpthread-2.23.so 7fb05b367000-7fb05b566000 ---p 00018000 fd:01 12838 /lib/x86_64-linux-gnu/libpthread-2.23.so 7fb05b566000-7fb05b567000 r--p 00017000 fd:01 12838 /lib/x86_64-linux-gnu/libpthread-2.23.so 7fb05b567000-7fb05b568000 rw-p 00018000 fd:01 12838 /lib/x86_64-linux-gnu/libpthread-2.23.so 7fb05b568000-7fb05b56c000 rw-p 00000000 00:00 0 7fb05b56c000-7fb05b592000 r-xp 00000000 fd:01 12833 /lib/x86_64-linux-gnu/ld-2.23.so 7fb05b5a7000-7fb05b5fd000 rw-p 00000000 00:00 0 7fb05b5fd000-7fb05b5fe000 ---p 00000000 00:00 0 7fb05b5fe000-7fb05b782000 rw-p 00000000 00:00 0 7fb05b782000-7fb05b791000 rw-p 00000000 00:00 0 7fb05b791000-7fb05b792000 r--p 00025000 fd:01 12833 /lib/x86_64-linux-gnu/ld-2.23.so 7fb05b792000-7fb05b793000 rw-p 00026000 fd:01 12833 /lib/x86_64-linux-gnu/ld-2.23.so 7fb05b793000-7fb05b794000 rw-p 00000000 00:00 0 7fff347b5000-7fff34fb4000 rw-p 00000000 00:00 0 [stack] 7fff34fdf000-7fff34fe1000 r--p 00000000 00:00 0 [vvar] 7fff34fe1000-7fff34fe3000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] [NOTE] You may have encountered a bug in the Ruby interpreter or extension libraries. Bug reports are welcome. For details: http://www.ruby-lang.org/bugreport.html ``` Running --dump=insns: ``` == disasm: #<ISeq:<main>@crash.rb>====================================== 0000 trace 1 ( 3) 0002 putobject_OP_INT2FIX_O_0_C_ ( 1) 0003 putobject_OP_INT2FIX_O_0_C_ ( 2) 0004 branchif 9 0006 putnil ( 3) 0007 jump 11 0009 putnil 0010 leave 0011 opt_gt <callinfo!mid:>, argc:1, ARGS_SIMPLE>, <callcache> 0014 leave ``` Ruby version output: ``` ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux] ``` I've attached the crash.rb file. The crash does not happen if I remove the "return" from the case statement, and the jump statement in the insns dump shows 10 instead of 11. Would a bug such as this be valid for this bounty, or should I report them directly to the ruby project? Cheers, Hugh