Bug #19084: Using `IO::Buffer` to change an extended String affects other Strings sharing the same buffer

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: master
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: DONE, 3.2: DONE

[jemmai (Jemma Issroff)]

When two extended Strings share a buffer, and one String's buffer changes, it currently affects the other String's buffer.

Here is a snippet to demonstrate this:

string = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"

other_string = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"

IO::Buffer.for(string) do |buffer|
  buffer.set_value(:U8, 0, "*".ord)
end

other_string[0] == "a"
# => false

Here is a PR which adds the above example as a test, and is currently failing CI.

(cc @ioquatix (Samuel Williams))

[jemmai (Jemma Issroff)]

• ruby -v set to 3.1.2

[jemmai (Jemma Issroff)]

• ruby -v changed from 3.1.2 to master

[ioquatix (Samuel Williams)]

This should be fixed by https://bugs.ruby-lang.org/issues/19084.

[ioquatix (Samuel Williams)]

Merged in https://github.com/ruby/ruby/commit/bd786e78969f9d4a8699376ceafe10934b6ad533.

[ioquatix (Samuel Williams)]

• Status changed from Open to Closed
• Backport changed from 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN to 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: REQUIRED to 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: DONE

ruby_3_2 c911cbd6c3dcc80def61ab48be1815cd910fc91b merged revision(s) bd786e78969f9d4a8699376ceafe10934b6ad533.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: DONE to 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: DONE, 3.2: DONE

ruby_3_1 3799270ec27b1267cd9923dae00bcb3955f7e061 merged revision(s) bd786e78969f9d4a8699376ceafe10934b6ad533.