Bug #20571: Compile error on for loop

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 3.1: REQUIRED, 3.2: DONE, 3.3: DONE

[kddnewton (Kevin Newton)]

for _ in 1.5 or _ in []
end

raises a compile error for the current compiler only with

-- raw disasm--------
   trace: 1
 <L000> [sp: 0, unremovable: 1, refcnt: 1]
   0000 putobject            1.5                                         (   1)
   0002 jump                 <L002>                                      (   1)
 <L006> [sp: 1, unremovable: 1, refcnt: 1]
 <L004> [sp: 1, unremovable: 0, refcnt: 0]
   0004 pop                                                              (   1)
*  0005 pop                                                              (   1)
   0006 putobject            false                                       (   1)
 <L002> [sp: 1, unremovable: 0, refcnt: 1]
   0008 send                 <calldata:each, 0>, nil                     (   1)
 <L001> [sp: -1, unremovable: 0, refcnt: 2]
   0011 leave                                                            (   1)
---------------------
test.rb:1: argument stack underflow (-1)
test.rb: compile error (SyntaxError)

[jeremyevans0 (Jeremy Evans)]

I looked into this and was able to determine the underlying cause (currently on line 7844 of compile.c):

ADD_INSN(cond_seq, line_node, pop); /* discard cached #deconstruct value */ 

Commenting that out fixes the example, though it causes overflow elsewhere. Most likely the pop instruction needs to be conditional, or we are missing a dup instruction somewhere.

[jeremyevans0 (Jeremy Evans)]

After some additional work, I think this is an optimizer issue. With --dump=i,-opt, both parse.y and prism generate the exact same instructions. However, with --dump=i, prism does not raise an error, but parse.y does. I'm not sure why the two would use different optimizers.

[mame (Yusuke Endoh)]

• Has duplicate Bug #20651: `false && (1 in 1)` produces argument stack underflow (-1) added

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN to 3.1: REQUIRED, 3.2: REQUIRED, 3.3: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 3.1: REQUIRED, 3.2: REQUIRED, 3.3: REQUIRED to 3.1: REQUIRED, 3.2: DONE, 3.3: REQUIRED

ruby_3_2 50399eebd96c76ce808ea4d84fe39693f585a531 merged revision(s) 1870505f478cc75993b296b7144a45137ace6937.

[k0kubun (Takashi Kokubun)]

• Backport changed from 3.1: REQUIRED, 3.2: DONE, 3.3: REQUIRED to 3.1: REQUIRED, 3.2: DONE, 3.3: DONE

ruby_3_3 6a4e79533b4454392f3afdfa0c4d35b763b68466.