Try to fix incorrect 64-bit alignment

Added unit tests for alignment macros.
Fixes #418

include/rapidjson/rapidjson.h

@@ -238,13 +238,13 @@
     \param x pointer to align
 
     Some machines require strict data alignment. Currently the default uses 4 bytes
-    alignment. User can customize by defining the RAPIDJSON_ALIGN function macro.,
+    alignment. User can customize by defining the RAPIDJSON_ALIGN function macro.
 */
 #ifndef RAPIDJSON_ALIGN
 #if RAPIDJSON_64BIT == 1
-#define RAPIDJSON_ALIGN(x) ((x + 7u) & ~7u)
+#define RAPIDJSON_ALIGN(x) (((x) + static_cast<uint64_t>(7u)) & ~static_cast<uint64_t>(7u))
 #else
-#define RAPIDJSON_ALIGN(x) ((x + 3u) & ~3u)
+#define RAPIDJSON_ALIGN(x) (((x) + 3u) & ~3u)
 #endif
 #endif
 

test/unittest/allocatorstest.cpp

@@ -61,3 +61,23 @@ TEST(Allocator, MemoryPoolAllocator) {
         EXPECT_LE(a.Size(), a.Capacity());
     }
 }
+
+TEST(Allocator, Alignment) {
+#if RAPIDJSON_64BIT == 1
+    EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000000), RAPIDJSON_ALIGN(0));
+    for (uint64_t i = 1; i < 8; i++) {
+        EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008), RAPIDJSON_ALIGN(i));
+        EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000000, 0x00000010), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0x00000008) + i));
+        EXPECT_EQ(RAPIDJSON_UINT64_C2(0x00000001, 0x00000000), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0x00000000, 0xFFFFFFF8) + i));
+        EXPECT_EQ(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF8), RAPIDJSON_ALIGN(RAPIDJSON_UINT64_C2(0xFFFFFFFF, 0xFFFFFFF0) + i));
+    }
+#else
+    EXPECT_EQ(0u, RAPIDJSON_ALIGN(0u));
+    for (uint32_t i = 1; i < 4; i++) {
+        EXPECT_EQ(4u, RAPIDJSON_ALIGN(i));
+        EXPECT_EQ(8u, RAPIDJSON_ALIGN(4u + i));
+        EXPECT_EQ(0xFFFFFFF8u, RAPIDJSON_ALIGN(0xFFFFFFF4u + i));
+        EXPECT_EQ(0xFFFFFFFCu, RAPIDJSON_ALIGN(0xFFFFFFF8u + i));
+    }
+#endif
+}