"ERROR(VpDivd): space for remainder too small" for certain division

[grk]

When upgrading to Ruby 3.1, I noticed a crashing edge-case when dividing by a certain number. It does not happen for bigdecimal < 3.1.1, but its 100% reproducible on 3.1.1.

The reproduction code is simple:

BigDecimal('1.0') / BigDecimal('3672577333.6608990499165058135986328125')

Happens on both linux and macos.

irb(main):001:0> BigDecimal::VERSION
=> "3.1.1"
irb(main):002:0> BigDecimal('63.0') / BigDecimal('3672577333.6608990499165058135986328125')
(irb):2: [BUG] ERROR(VpDivd): space for remainder too small.
ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x86_64-linux]

-- Control frame information -----------------------------------------------
c:0034 p:---- s:0198 e:000197 CFUNC  :/
c:0033 p:0012 s:0193 e:000192 EVAL   (irb):2 [FINISH]
c:0032 p:---- s:0190 e:000189 CFUNC  :eval
c:0031 p:0020 s:0182 e:000181 METHOD /usr/local/lib/ruby/3.0.0/irb/workspace.rb:116
c:0030 p:0059 s:0174 e:000172 METHOD /usr/local/lib/ruby/3.0.0/irb/context.rb:450

Further debug info is I think irrelevant, but I can attach if needed.

[mrkn]

@grk Thank you for reporting this!

[mathieujobin]

We still encountered this on 3.1.4

irb(main):004:0> comp.send(:pay_per_time_base).class
=> BigDecimal
irb(main):005:0> comp.send(:pay_per_time_base)
=> 0.22e5
irb(main):006:0> comp.send(:hours_per_month)
=> 0.2095999999999999999999999999999999999968e3
irb(main):007:0> comp.send(:hours_per_month).class
=> BigDecimal
irb(main):008:0> comp.send(:pay_per_time_base) / comp.send(:hours_per_month)
(irb):8: [BUG] ERROR(VpDivd): space for remainder too small.
ruby 3.1.4p223 (2023-03-30 revision 957bb7cb81) [x86_64-linux]                 
                                                                               
-- Control frame information -----------------------------------------------   
c:0030 p:---- s:0170 e:000169 CFUNC  :/                                        
c:0029 p:0014 s:0165 e:000164 EVAL   (irb):8 [FINISH]                          
c:0028 p:---- s:0162 e:000161 CFUNC  :eval                                     
c:0027 p:0020 s:0154 e:000153 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb/workspace.rb:119
c:0026 p:0054 s:0146 e:000144 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb/context.rb:476
c:0025 p:0161 s:0137 e:000136 BLOCK  /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:577
c:0024 p:0024 s:0132 e:000131 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:770
c:0023 p:0007 s:0126 e:000125 BLOCK  /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:558
c:0022 p:0123 s:0121 e:000120 BLOCK  /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb/ruby-lex.rb:268 [FINISH]
c:0021 p:---- s:0117 e:000116 CFUNC  :loop
c:0020 p:0005 s:0113 e:000112 BLOCK  /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb/ruby-lex.rb:250 [FINISH]
c:0019 p:---- s:0110 e:000109 CFUNC  :catch
c:0018 p:0010 s:0105 e:000104 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb/ruby-lex.rb:249
c:0017 p:0047 s:0101 E:000f78 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:557
c:0016 p:0003 s:0096 e:000095 BLOCK  /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:491 [FINISH]
c:0015 p:---- s:0093 e:000092 CFUNC  :catch
c:0014 p:0057 s:0088 E:0018a0 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:490
c:0013 p:0104 s:0082 e:000081 METHOD /usr/local/rvm/rubies/ruby-3.1.4/lib/ruby/3.1.0/irb.rb:419

[mathieujobin]

Revisiting this...

Ruby 3.0.6

(BigDecimal('22000.0') / (BigDecimal('9.6') * (BigDecimal('262.0') / BigDecimal(12)))).to_s
=> "104.961832061068702291678806596352193928117233688"

Ruby 3.1.4

BigDecimal('22000.0') / (BigDecimal('9.6') * (BigDecimal('262.0') / BigDecimal(12)))
(pry):4: [BUG] ERROR(VpDivd): space for remainder too small.

Ruby 3.2.2

(BigDecimal('22000.0') / (BigDecimal('9.6') * (BigDecimal('262.0') / BigDecimal(12)))).to_s
=> "104.961832061068702290076335877862595421449798962764407668550783753860497640022134335"

Only 3.1 is affected.