Bug #13135: Regexp.last_match returns nil with s.rindex(//)

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.2: DONE, 2.3: DONE, 2.4: DONE

[shugo (Shugo Maeda)]

Regexp.last_match returns nil, if // is given to String#rindex:

lexington:ruby$ ruby -ve 'p "foo".rindex(//); p Regexp.last_match'
ruby 2.5.0dev (2017-01-17 trunk 57359) [x86_64-linux]
3
nil

while it returns a MatchData with String#index:

lexington:ruby$ ruby -ve 'p "foo".index(//); p Regexp.last_match' 
ruby 2.5.0dev (2017-01-17 trunk 57359) [x86_64-linux]
0
#<MatchData "">

Is this intended behavior?

[shugo (Shugo Maeda)]

Shugo Maeda wrote:

Regexp.last_match returns nil, if // is given to String#rindex:

The following patch seems to fix it:

diff --git a/string.c b/string.c
index 919a46d..b5aae67 100644
--- a/string.c
+++ b/string.c
@@ -3516,10 +3516,8 @@ rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
 	pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
 			 enc, single_byte_optimizable(str));
 
-	if (!RREGEXP_PTR(sub) || RREGEXP_SRC_LEN(sub)) {
-	    pos = rb_reg_search(sub, str, pos, 1);
-	    pos = rb_str_sublen(str, pos);
-	}
+	pos = rb_reg_search(sub, str, pos, 1);
+	pos = rb_str_sublen(str, pos);
 	if (pos >= 0) return LONG2NUM(pos);
 	break;
 

[shugo (Shugo Maeda)]

• Status changed from Open to Closed

Applied in changeset r57374.

---

string.c: rindex(//) should set $~.

This seems a bug introduced by r520 (1.4.0). [ruby-core:79110] [Bug #13135]

[naruse (Yui NARUSE)]

• Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN to 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: DONE

ruby_2_4 r57864 merged revision(s) 57374.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: DONE to 2.2: REQUIRED, 2.3: REQUIRED, 2.4: DONE

[usa (Usaku NAKAMURA)]

• Backport changed from 2.2: REQUIRED, 2.3: REQUIRED, 2.4: DONE to 2.2: DONE, 2.3: REQUIRED, 2.4: DONE

ruby_2_2 r58098 merged revision(s) 57374.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.2: DONE, 2.3: REQUIRED, 2.4: DONE to 2.2: DONE, 2.3: DONE, 2.4: DONE

ruby_2_3 r58176 merged revision(s) 57374.