Bug #14900
Updated by janko (Janko Marohnić) almost 6 years ago
When executing `String#byteslice` with a range, I noticed that sometimes the original string is allocated again. When I run the following script:
~~~ ruby
require "objspace"
string = "a" * 100_000
GC.start
GC.disable
generation = GC.count
ObjectSpace.trace_object_allocations do
string.byteslice(50_000..-1)
ObjectSpace.each_object(String) do |string|
p string.bytesize if ObjectSpace.allocation_generation(string) == generation
end
end
~~~
it outputs
~~~
50000
100000
6
5
~~~
The one with 50000 bytes is the result of `String#byteslice`, but the one with 100000 bytes is the duplicated original string. I expected only the result of `String#byteslice` to be amongst new allocations.
If instead of the last 50000 bytes I slice the *first* 50000 bytes, the extra duplication doesn't occur.
~~~ ruby
# ...
string.byteslice(0, 50_000)
# ...
~~~
~~~
50000
5
~~~
It's definitely ok if the implementation of `String#bytesize` allocates extra strings as part of the implementation, but it would be nice if they were deallocated before returning the result.
EDIT: It seems that `String#slice` has the same issue.