Issue #22126 has been updated by rwstauner (Randy Stauner). Backport PR for ruby_4_0 (4.0) opened: https://github.com/ruby/ruby/pull/17511 ---------------------------------------- Bug #22126: Stack underflow for partial DCE and loops https://bugs.ruby-lang.org/issues/22126#change-117772 * Author: viralpraxis (Iaroslav Kurbatov) * Status: Closed * ruby -v: ruby 4.1.0dev (2026-06-23T13:29:36Z master 13fe77dd2b) +PRISM [x86_64-linux] * Backport: 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED ---------------------------------------- ``` ruby ruby --parser prism -e 'if []; else; a => [*, 42, *]; end' -- raw disasm-------- trace: 1 0000 putnil ( 1) 0001 leave ( 1) <L018> [sp: 1, unremovable: 0, refcnt: 1] 0002 dup ( 1) 0003 topn 2 ( 1) 0005 opt_le <calldata:<=, 1> ( 1) 0007 branchunless <L021> ( 1) 0009 topn 3 ( 1) 0011 topn 1 ( 1) 0013 opt_aref <calldata:[], 1> ( 1) 0015 putobject 42 ( 1) 0017 dupn 2 ( 1) 0019 checkmatch 2 ( 1) 0021 dup ( 1) 0022 branchif <L023> ( 1) 0024 putspecialobject 1 ( 1) 0026 putobject "%p === %p does not return true" ( 1) 0028 topn 3 ( 1) 0030 topn 5 ( 1) 0032 opt_send_without_block <calldata:core#sprintf, 3> ( 1) 0034 setn 10 ( 1) 0036 putobject false ( 1) 0038 setn 12 ( 1) 0040 pop ( 1) 0041 pop ( 1) <L023> [sp: 4, unremovable: 0, refcnt: 1] 0042 setn 2 ( 1) 0044 pop ( 1) 0045 pop ( 1) 0046 branchif <L020> ( 1) 0048 putobject_INT2FIX_1_ ( 1) 0049 opt_plus <calldata:+, 1> ( 1) 0051 jump <L018> ( 1) <L021> [sp: 1, unremovable: 0, refcnt: 1] * 0053 adjuststack 3 ( 1) 0055 putspecialobject 1 ( 1) 0057 putobject "%p does not match to find pattern" ( 1) 0059 topn 2 ( 1) 0061 opt_send_without_block <calldata:core#sprintf, 2> ( 1) 0063 setn 4 ( 1) 0065 putobject false ( 1) 0067 setn 6 ( 1) 0069 pop ( 1) 0070 pop ( 1) 0071 jump <L012> ( 1) <L020> [sp: 1, unremovable: 0, refcnt: 1] 0073 adjuststack 3 ( 1) 0075 pop ( 1) 0076 jump <L003> ( 1) <L012> [sp: -1, unremovable: 0, refcnt: 1] 0078 pop ( 1) 0079 putspecialobject 1 ( 1) 0081 topn 4 ( 1) 0083 branchif <L024> ( 1) 0085 putobject NoMatchingPatternError ( 1) 0087 putspecialobject 1 ( 1) 0089 putobject "%p: %s" ( 1) 0091 topn 4 ( 1) 0093 topn 7 ( 1) 0095 opt_send_without_block <calldata:core#sprintf, 3> ( 1) 0097 opt_send_without_block <calldata:core#raise, 2> ( 1) 0099 jump <L025> ( 1) <L024> [sp: -1, unremovable: 0, refcnt: 1] 0101 putobject NoMatchingPatternKeyError ( 1) 0103 putspecialobject 1 ( 1) 0105 putobject "%p: %s" ( 1) 0107 topn 4 ( 1) 0109 topn 7 ( 1) 0111 opt_send_without_block <calldata:core#sprintf, 3> ( 1) 0113 topn 7 ( 1) 0115 topn 9 ( 1) 0117 opt_send_without_block <calldata:new, 3> ( 1) 0119 opt_send_without_block <calldata:core#raise, 1> ( 1) <L025> [sp: -1, unremovable: 0, refcnt: 1] 0121 adjuststack 7 ( 1) 0123 putnil ( 1) 0124 leave ( 1) <L003> [sp: -1, unremovable: 0, refcnt: 1] 0125 adjuststack 6 ( 1) 0127 putnil ( 1) 0128 leave ( 1) --------------------- -e:1: argument stack underflow (-2) -e: compile error (SyntaxError) ``` proposed patch: https://github.com/ruby/ruby/pull/17449 every version since 3.4.0-preview2 is affected -- https://bugs.ruby-lang.org/