Issue #15926 has been updated by jeremyevans0 (Jeremy Evans).

File str-uminus-freeze-fix-v2.patch added

luke-gru (Luke Gruber) wrote:
> Hi Jeremy, thanks for the patch. I agree with the strategy of just dealing with this in `str_uminus` directly instead of fiddling around in the tricky `rb_fstring` function. However there's still an issue when the string is a regular String, but tainted or has ivars. In this case, it still gets frozen. I think the check should be something like:
> 
> ```
> if (!BARE_STRING_P(str) && !rb_obj_frozen_p(str)) {
>      str = rb_str_dup(str);
> }
> ```

I agree, that is a better way to go.  Attached is a new patch that does that and adds a couple more tests.

----------------------------------------
Bug #15926: Edge case issue with String#uminus
https://bugs.ruby-lang.org/issues/15926#change-78704

* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
I was working on issue related to code in `rb_fstring`(https://github.com/ruby/ruby/pull/2233) and saw some weird behavior in the function,
freezing the given string if it's not a "bare" string and it's small enough to be embedded.

The issue comes up in the following edge case:

class MyString < String
end
non_frozen = MyString.new("nonfrozen")
frozen = -non_frozen # deduplicates, but shouldn't freeze receiver
non_frozen << " added" # raises FrozenError

I'm not sure what the correct behavior should be with a subclass and String#uminus. Should it return
a frozen regular String or a frozen copy of the given class's string?

Not a practical concern (not often come upon I'm sure), but I think a valid one.

---Files--------------------------------
str-uminus-freeze-fix.patch (1.38 KB)
str-uminus-freeze-fix-v2.patch (1.58 KB)


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