merge revision(s) f54369830f83a65fb54916d762883fbe6eeb7d0b, 338eb0065bd81ba8ae8b9402abc94804a24594cc, ac636f5709feb1d9d7a0c46a86be153be765cf21: [Backport #20516]

	Revert "Rollback to released version numbers of stringio and strscan"

	This reverts commit 6a79e53823e328281b9e9eee53cd141af28f8548.

	[ruby/strscan] StringScanner#captures: Return nil not "" for unmached capture (https://github.com/ruby/strscan/pull/72)

	fix https://github.com/ruby/strscan/issues/70
	If there is no substring matching the group (s[3]), the behavior is
	different.

	If there is no substring matching the group, the corresponding element
	(s[3]) should be nil.

	```
	s = StringScanner.new('foobarbaz') #=> #<StringScanner 0/9 @ "fooba...">
	s.scan /(foo)(bar)(BAZ)?/  #=> "foobar"
	s[0]           #=> "foobar"
	s[1]           #=> "foo"
	s[2]           #=> "bar"
	s[3]           #=> nil
	s.captures #=> ["foo", "bar", ""]
	s.captures.compact #=> ["foo", "bar", ""]
	```

	```
	s = StringScanner.new('foobarbaz') #=> #<StringScanner 0/9 @ "fooba...">
	s.scan /(foo)(bar)(BAZ)?/  #=> "foobar"
	s[0]           #=> "foobar"
	s[1]           #=> "foo"
	s[2]           #=> "bar"
	s[3]           #=> nil
	s.captures #=> ["foo", "bar", nil]
	s.captures.compact #=> ["foo", "bar"]
	```

	https://docs.ruby-lang.org/ja/latest/method/MatchData/i/captures.html
	```
	/(foo)(bar)(BAZ)?/ =~ "foobarbaz" #=> 0
	$~.to_a        #=> ["foobar", "foo", "bar", nil]
	$~.captures #=> ["foo", "bar", nil]
	$~.captures.compact #=> ["foo", "bar"]
	```

	* StringScanner#captures is not yet documented.
	https://docs.ruby-lang.org/ja/latest/class/StringScanner.html

	https://github.com/ruby/strscan/commit/1fbfdd3c6f

	[ruby/strscan] Bump version

	https://github.com/ruby/strscan/commit/d6f97ec102

2 files changed, 13 insertions, 9 deletions

diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 7eade5bcba..74e2b95c99 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -13,7 +13,7 @@
 **********************************************************************/
 
 static const char *const
-STRINGIO_VERSION = "3.1.0";
+STRINGIO_VERSION = "3.1.1";
 
 #include "ruby.h"
 #include "ruby/io.h"
diff --git a/ext/strscan/strscan.c b/ext/strscan/strscan.c
index 16d669d8a5..4598d13c90 100644
--- a/ext/strscan/strscan.c
+++ b/ext/strscan/strscan.c
@@ -22,7 +22,7 @@ extern size_t onig_region_memsize(const struct re_registers *regs);
 
 #include <stdbool.h>
 
-#define STRSCAN_VERSION "3.0.7"
+#define STRSCAN_VERSION "3.0.9"
 
 /* =======================================================================
                          Data Type Definitions
@@ -1243,10 +1243,10 @@ strscan_size(VALUE self)
  * If nothing was priorly matched, it returns nil.
  *
  *   s = StringScanner.new("Fri Dec 12 1975 14:39")
- *   s.scan(/(\w+) (\w+) (\d+) /)       # -> "Fri Dec 12 "
- *   s.captures                         # -> ["Fri", "Dec", "12"]
- *   s.scan(/(\w+) (\w+) (\d+) /)       # -> nil
- *   s.captures                         # -> nil
+ *   s.scan(/(\w+) (\w+) (\d+) (1980)?/)       # -> "Fri Dec 12 "
+ *   s.captures                                # -> ["Fri", "Dec", "12", nil]
+ *   s.scan(/(\w+) (\w+) (\d+) (1980)?/)       # -> nil
+ *   s.captures                                # -> nil
  */
 static VALUE
 strscan_captures(VALUE self)
@@ -1262,9 +1262,13 @@ strscan_captures(VALUE self)
     new_ary  = rb_ary_new2(num_regs);
 
     for (i = 1; i < num_regs; i++) {
-        VALUE str = extract_range(p,
-                                  adjust_register_position(p, p->regs.beg[i]),
-                                  adjust_register_position(p, p->regs.end[i]));
+        VALUE str;
+        if (p->regs.beg[i] == -1)
+            str = Qnil;
+        else
+            str = extract_range(p,
+                                adjust_register_position(p, p->regs.beg[i]),
+                                adjust_register_position(p, p->regs.end[i]));
         rb_ary_push(new_ary, str);
     }