# \*, z = 1 breaks stack consistency

**URL:** <https://www.ruby-forum.com/t/z-1-breaks-stack-consistency/124502>\
**Category:** Development\
**Created:** [December 29, 2007, 9:37am UTC](https://www.ruby-forum.com/t/z-1-breaks-stack-consistency/124502 "2007-12-29T09:37:49Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [December 29, 2007, 9:37am UTC](https://www.ruby-forum.com/t/z-1-breaks-stack-consistency/124502/1 "2007-12-29T09:37:49Z")

</div>

e$B1sF#$H?=$7$^$9!#e(B

1.9 e$B$,0J2\<$GMn$A$^$9!#e(B

$ ./ruby -e ‘while true; \*, z = 1; break; end’  
-e:1: [BUG] Stack consistency error (sp: 8, bp: 7)  
ruby 1.9.0 (2007-12-29 revision 0) [i686-linux]

## – control frame ---------- c:0003 p:0018 s:0008 b:0007 l:000006 d:000006 TOP -e:1 c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH :inherited c:0001 p:0000 s:0002 b:0002 l:000001 d:000001 TOP :17

## – backtrace of native function call (Use addr2line) – 0x80eda15 0x810c3be 0x810c41b 0x80eac76 0x80eb454 0x80eb78b 0x805a3f9 0x805e2e0 0x8057f51 0xb7e03ea8 0x8057e61

e$B%"%!\<%H$7$^$7$?e(B

expandarray e$B$Ne(B sp e$B$ND4@0$,$\*$+$7$$$H;W$$$^$9!#e(Bvm\_expandarray  
e$B$G$Oe(B  
sp += num + is\_splat e$B$H$7$F$$$k$@$1$J$N$G!"F1$8$h$&$K$9$Y$-$G$Oe(B  
e$B$J$$$G$7$g$&$+!#e(B

# Index: insns.def

— insns.def (revision 14780)  
+++ insns.def (working copy)  
@@ -451,7 +451,7 @@  
expandarray  
(rb\_num\_t num, rb\_num\_t flag)  
(…, VALUE ary)  
-(…) // inc += flag == 0x02 ? num : ((num \> 0) ? num - 1 + (flag ? 1  
: 0) : num + 1 - (flag ? 1 : 0));  
+(…) // inc += num - 1 + (flag & 1 ? 1 : 0);  
{  
vm\_expandarray(GET\_CFP(), ary, num, flag);  
}