rb_str_set_len should clear code range
rb_str_set_len on a
String could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a
CR_UNKNOWN code range, there's no problem because the correct values will lazily calculated.
An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:
@str = "abcdefghij"[0..-1] @s.rb_str_set_len(@str, 1) @str.should == "a" @str.force_encoding(Encoding::UTF_8) @str.valid_encoding?.should == true @s.RSTRING_PTR_set(@str, 1, 'B'.ord) @s.RSTRING_PTR_set(@str, 2, 0x80) @s.rb_str_set_len(@str, 3) p @str @str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.
The first call to
valid_encoding? forces the code range to be calculated for the string and it's determined to be
rb_str_set_len is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as
CR_7BIT, but the byte sequence is invalid for UTF-8.
I think the fix is a simple matter of clearing the code range in
rb_str_set_len, but I'd appreciate a review of my analysis.