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Bug #9079
closed
Interpolated Symbol creates unnecessary intermediate String on the heap
Bug #9079: Interpolated Symbol creates unnecessary intermediate String on the heap
Description
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.
Updated by Anonymous about 12 years ago
To shed a bit of light on why this happens, it turns out :"" syntax is just sugar for "".intern:
~ trunk λ 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 
Updated by ko1 (Koichi Sasada) almost 12 years ago
- Target version set to 2.6
Does it has huge impact?
It is easy to add an instruction (replace concatstrings to concatstrings_and_make_it_symbol) or add a method like that.
However, it has a bit problem about encoding.
Current implementation is easy and safe, because we can catch up encoding related change to String.
I want to remain this issue, if this does not have huge impact for performance.
Updated by ko1 (Koichi Sasada) about 10 years ago
- Status changed from Open to Feedback
Updated by jeremyevans0 (Jeremy Evans) over 6 years ago
- Status changed from Feedback to Closed
- Backport deleted (
1.9.3: UNKNOWN, 2.0.0: UNKNOWN)
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