Remove Encoding of values in char** For Labels (pandas-dev#27618)

doc/source/whatsnew/v1.0.0.rst

@@ -159,6 +159,7 @@ I/O
 ^^^
 
 - :meth:`read_csv` now accepts binary mode file buffers when using the Python csv engine (:issue:`23779`)
+- Bug in :meth:`DataFrame.to_json` where using a Tuple as a column or index value and using ``orient="columns"`` or ``orient="index"`` would produce invalid JSON (:issue:`20500`)
 -
 
 Plotting

pandas/_libs/src/ujson/lib/ultrajson.h

@@ -307,11 +307,4 @@ EXPORTFUNCTION JSOBJ JSON_DecodeObject(JSONObjectDecoder *dec,
                                        const char *buffer, size_t cbBuffer);
 EXPORTFUNCTION void encode(JSOBJ, JSONObjectEncoder *, const char *, size_t);
 
-#define Buffer_Reserve(__enc, __len)                                  \
-    if ((size_t)((__enc)->end - (__enc)->offset) < (size_t)(__len)) { \
-        Buffer_Realloc((__enc), (__len));                             \
-    }
-
-void Buffer_Realloc(JSONObjectEncoder *enc, size_t cbNeeded);
-
 #endif  // PANDAS__LIBS_SRC_UJSON_LIB_ULTRAJSON_H_

pandas/_libs/src/ujson/lib/ultrajsonenc.c

@@ -714,6 +714,12 @@ int Buffer_EscapeStringValidated(JSOBJ obj, JSONObjectEncoder *enc,
     }
 }
 
+#define Buffer_Reserve(__enc, __len) \
+    if ( (size_t) ((__enc)->end - (__enc)->offset) < (size_t) (__len))  \
+    {   \
+      Buffer_Realloc((__enc), (__len));\
+    }   \
+
 #define Buffer_AppendCharUnchecked(__enc, __chr) *((__enc)->offset++) = __chr;
 
 FASTCALL_ATTR INLINE_PREFIX void FASTCALL_MSVC strreverse(char *begin,