Fix a bug in dtoa

This previously affects Writer:: SetMaxDecimalPlaces()

include/rapidjson/internal/dtoa.h

@@ -180,7 +180,7 @@ inline char* Prettify(char* buffer, int length, int k, int maxDecimalPlaces) {
         buffer[1] = '.';
         for (int i = 2; i < offset; i++)
             buffer[i] = '0';
-        if (length + offset > maxDecimalPlaces) {
+        if (length - kk > maxDecimalPlaces) {
             // When maxDecimalPlaces = 2, 0.123 -> 0.12, 0.102 -> 0.1
             // Remove extra trailing zeros (at least one) after truncation.
             for (int i = maxDecimalPlaces + 1; i > 2; i--)

test/unittest/dtoatest.cpp

@@ -81,6 +81,12 @@ TEST(dtoa, maxDecimalPlaces) {
     TEST_DTOA(3, 2.225073858507201e-308, "0.0"); // Max subnormal positive double
     TEST_DTOA(3, 2.2250738585072014e-308, "0.0"); // Min normal positive double
     TEST_DTOA(3, 1.7976931348623157e308, "1.7976931348623157e308"); // Max double
+    TEST_DTOA(5, -0.14000000000000001, "-0.14");
+    TEST_DTOA(4, -0.14000000000000001, "-0.14");
+    TEST_DTOA(3, -0.14000000000000001, "-0.14");
+    TEST_DTOA(3, -0.10000000000000001, "-0.1");
+    TEST_DTOA(2, -0.10000000000000001, "-0.1");
+    TEST_DTOA(1, -0.10000000000000001, "-0.1");
 
 #undef TEST_DTOA
 }