Bug #15816
closedString#casecmp compares uppercase characters instead of lowercase
Description
The current implementation of String#casecmp
converts characters to uppercase before comparing them. However, all references I've found for strcasecmp
(the C function on which String#casecmp
is based) indicate characters should be converted to lowercase before being compared.
For example, this man page says:
The POSIX.1-2008 standard says ... shall behave as if the strings had been converted to lowercase and then a byte comparison performed.
The difference in behavior is apparent when comparing / sorting strings containing [
, \
, ]
, ^
, _
, or `
(the characters that occur between Z
and a
). Converting to lowercase sorts these punctuation characters before A
-z
along with most of the other punctuation in ASCII, but converting to uppercase sorts these characters after A
-z
instead.
Files
Updated by jeremyevans0 (Jeremy Evans) almost 5 years ago
- File casecmp-lowercase.patch casecmp-lowercase.patch added
The documentation of String#casecmp
does not specify how it is is implemented, so it seems fair to consider switching. However, this change is likely to cause backwards compatibility issues. While it seems unlikely there are many applications relying on the current behavior, I would guess there are at least a few.
Considering that String#casecmp?
uses lowercase and not uppercase, I think making such a change is reasonable, but we may want to delay making this change until Ruby 3.
Attached is a patch if we want to make this change.
Updated by mame (Yusuke Endoh) almost 5 years ago
Until ruby 1.8.7, it seemed to use downcase. It was changed at r14227 to support encoding. I think the behavior change was not intended, so this is merely a bug?
# ./bin/ruby-1.8.7-p374 -e 'p "a".casecmp("[")'
1
# ./bin/ruby-1.9.0-0 -e 'p "a".casecmp("[")'
-1
Updated by nobu (Nobuyoshi Nakada) almost 5 years ago
Indeed, rb_enc_upper
is used at https://github.com/ruby/ruby/commit/269bd16b28e86d1333969389b7b402f2915e336f#diff-7a2f2c7dfe0bf61d38272aeaf68ac768R1431, while previous rb_memcicmp
maps to the lowercase.
Updated by jeremyevans0 (Jeremy Evans) over 4 years ago
- Status changed from Open to Closed
Fixed in 082424ef58116db9663a754157d6c441d60fd101.