merge revision(s) 3f54d09a5b8b6e4fd734abc8911e170d5967b5b0: [Backport #19390]

	bignum.c: rb_int_parse_cstr handle `0` strings

	[Bug #19390]

	We shouldn't check the string length when skipping zeros, as the
	string might only contains zero characters, resulting in an empty string.
	---
	 bignum.c               | 1 -
	 test/ruby/test_time.rb | 4 ++++
	 2 files changed, 4 insertions(+), 1 deletion(-)

3 files changed, 5 insertions, 2 deletions

diff --git a/bignum.c b/bignum.c
index 4f8349dd17..8ef19e9751 100644
--- a/bignum.c
+++ b/bignum.c
@@ -4184,7 +4184,6 @@ rb_int_parse_cstr(const char *str, ssize_t len, char **endp, size_t *ndigits,
         }
         if (!c || ISSPACE(c)) --str;
         if (end) len = end - str;
-        ASSERT_LEN();
     }
     c = *str;
     c = conv_digit(c);
diff --git a/test/ruby/test_time.rb b/test/ruby/test_time.rb
index 38c1af6901..2bf6056a49 100644
--- a/test/ruby/test_time.rb
+++ b/test/ruby/test_time.rb
@@ -1426,4 +1426,8 @@ class TestTime < Test::Unit::TestCase
       t.deconstruct_keys(%i[year month sec nonexistent])
     )
   end
+
+  def test_parse_zero_bigint
+    assert_equal 0, Time.new("2020-10-28T16:48:07.000Z").nsec, '[Bug #19390]'
+  end
 end
diff --git a/version.h b/version.h
index 13b490f2c4..a26c469164 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 0
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 22
+#define RUBY_PATCHLEVEL 23
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"