Bug #11970: Multiple Assignment Into a Hash with Destructuring causes segfault

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
• Backport: 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE, 2.3: DONE

[dwahl (Davis Wahl)]

Segfaults in 2.2.3 and 2.3.0, In 2.1.0 and below, produces {[:foo]=>:bar}

foo = [:foo]
bar = [:bar]

h = {}
h[*foo], _tail = *bar # Segfault

Using hash assignment/destructuring in this way may very well be undefined. I am surprised that the hash key h[*foo] destructures in later examples, but I'm not really sure what the behavior should be. A number of similar constructs
produce consistent behavior, which leads me to believe the above syntax should work (or at least not segfault).

Below examples produce the same output in ruby 1.9.3, 2.1.0, 2.2.3, and 2.3.0

h = {}
h[:foo], _tail = *bar
puts h
# => {:foo => :bar}

h = {}
h[foo[0]], _tail = *bar
puts h
# => {:foo => :bar}

h = {}
h[*foo] = :bar
puts h
# => {:foo => :bar}

Rubies Tested:

ruby 1.9.3p550 (2014-10-27 revision 48165) [x86_64-linux]
ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-linux]
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]

[dwahl (Davis Wahl)]

I apologize for whatever I did to mangle the formatting.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED

Seems incorrect results also in 2.0 and 2.1.

[nobu (Nobuyoshi Nakada)]

https://github.com/nobu/ruby/tree/bug/11970-massign-lhs-splat

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset r53495.

---

compile.c: fix lhs splat in massign

• compile.c (compile_massign_lhs): when index ends with splat,
  append rhs value to it like POSTARG, since VM_CALL_ARGS_SPLAT
  splats the last argument only. [ruby-core:72777] [Bug #11970]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: DONE

ruby_2_3 r54478 merged revision(s) 53495.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: DONE to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE, 2.3: DONE

ruby_2_2 r54671 merged revision(s) 53495.