Fix parsing of *negative* out of bound floats.

Author: byroot

ext/json/ext/parser/parser.c

@@ -864,11 +864,11 @@ static inline VALUE json_decode_float(JSON_ParserConfig *config, uint64_t mantis
     }
 
     if (RB_UNLIKELY(exponent > INT32_MAX)) {
-        return CInfinity;
+        return negative ? CMinusInfinity : CInfinity;
     }
 
     if (RB_UNLIKELY(exponent < INT32_MIN)) {
-        return rb_float_new(0.0);
+        return rb_float_new(negative ? -0.0 : 0.0);
     }
 
     // Fall back to rb_cstr_to_dbl for potential subnormals (rare edge case)

test/json/json_ryu_fallback_test.rb

@@ -173,5 +173,11 @@ def test_large_exponent_numbers
     assert_equal 0.0, JSON.parse("99999999999999999e-4294967296")
     assert_equal Float::INFINITY, JSON.parse("1e4294967295")
     assert_equal Float::INFINITY, JSON.parse("1e4294967297")
+
+    assert_equal -Float::INFINITY, JSON.parse("-1e4294967296")
+    assert_equal -0.0, JSON.parse("-1e-4294967296")
+    assert_equal -0.0, JSON.parse("-99999999999999999e-4294967296")
+    assert_equal -Float::INFINITY, JSON.parse("-1e4294967295")
+    assert_equal -Float::INFINITY, JSON.parse("-1e4294967297")
   end
 end