From: "charliesome (Charlie Somerville)" <charliesome@...>
Date: 2013-11-05T08:06:38+09:00
Subject: [ruby-core:58161] [ruby-trunk - Bug #9079] Interpolated Symbol	creates unnecessary intermediate String on the heap


Issue #9079 has been updated by charliesome (Charlie Somerville).


To shed a bit of light on why this happens, it turns out :"" syntax is just sugar for "".intern:

    ~ trunk �� ruby --dump=insns -e ':"hello #{123}"'
    == disasm: <RubyVM::InstructionSequence:<main>@-e>======================
    0000 trace            1                                               (   1)
    0002 putobject        "hello "
    0004 putobject        123
    0006 tostring
    0007 concatstrings    2
    0009 opt_send_simple  <callinfo!mid:intern, argc:0, ARGS_SKIP>
    0011 leave
----------------------------------------
Bug #9079: Interpolated Symbol creates unnecessary intermediate String on the heap
https://bugs.ruby-lang.org/issues/9079#change-42747

Author: wycats (Yehuda Katz)
Status: Open
Priority: Normal
Assignee: ko1 (Koichi Sasada)
Category: 
Target version: 
ruby -v: ruby 2.0.0p343 (2013-10-31) [x86_64-linux]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


This case:

  x = "world"
  y = :"hello#{world}!"

allocates one T_STRING according to ObjectSpace.count_objects. Since all of the concatenation happens as part of the symbol generation, it shouldn't be necessary to create a Ruby string.


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