Issue #15151 has been updated by chopraanmol1 (Anmol Chopra).


@nobu can you look into this? Thank you. 

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Bug #15151: String#slice!(0,..) creates a duplicate of original string
https://bugs.ruby-lang.org/issues/15151#change-74262

* Author: chopraanmol1 (Anmol Chopra)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0dev (2018-09-23 trunk 64815) [x86_64-linux]
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
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String#slice! when used at beginning of string (e.g. slice!(0,10)) calls rb_str_drop_bytes which creates shared string for non embedded string. str_modify_keep_cr clears the flag of shared string which is called before rb_str_drop_bytes. Due to which while calling slice! multiple time on same string creates multiple duplicate string.

Patch:

https://github.com/ruby/ruby/pull/1961

Comparison:
trunk:
~~~
Total allocated: 141116188 bytes (11250 objects)

  0.048000   0.000000   0.048000 (  0.045974)
~~~

patch:
~~~
Total allocated: 300080 bytes (7502 objects)

  0.016000   0.004000   0.020000 (  0.017376)
~~~

---Files--------------------------------
bench_slice_bang.rb (412 Bytes)


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