BUG: fix memory leak in JSON datetime serialization (#62217)

Author: Alvaro-Kothe

pandas/_libs/src/vendored/ujson/python/objToJSON.c

@@ -51,6 +51,8 @@ Numeric decoder derived from TCL library
 #include <numpy/ndarraytypes.h>
 #include <numpy/npy_math.h>
 
+static const int CSTR_SIZE = 20;
+
 npy_int64 get_nat(void) { return NPY_MIN_INT64; }
 
 typedef const char *(*PFN_PyTypeToUTF8)(JSOBJ obj, JSONTypeContext *ti,
@@ -106,7 +108,7 @@ typedef struct __TypeContext {
  double doubleValue;
  JSINT64 longValue;
 
- const char *cStr;
+ char *cStr;
  NpyArrContext *npyarr;
  PdBlockContext *pdblock;
  int transpose;
@@ -347,7 +349,8 @@ static const char *PyDateTimeToIsoCallback(JSOBJ obj, JSONTypeContext *tc,
  }
 
  NPY_DATETIMEUNIT base = ((PyObjectEncoder *)tc->encoder)->datetimeUnit;
- return PyDateTimeToIso(obj, base, len);
+ GET_TC(tc)->cStr = PyDateTimeToIso(obj, base, len);
+ return GET_TC(tc)->cStr;
 }
 
 static const char *PyTimeToJSON(JSOBJ _obj, JSONTypeContext *tc,
@@ -1007,16 +1010,24 @@ static const char *List_iterGetName(JSOBJ Py_UNUSED(obj),
 //=============================================================================
 static void Index_iterBegin(JSOBJ Py_UNUSED(obj), JSONTypeContext *tc) {
  GET_TC(tc)->index = 0;
+ GET_TC(tc)->cStr = PyObject_Malloc(CSTR_SIZE);
+ if (!GET_TC(tc)->cStr) {
+ PyErr_NoMemory();
+ }
 }
 
 static int Index_iterNext(JSOBJ obj, JSONTypeContext *tc) {
  const Py_ssize_t index = GET_TC(tc)->index;
  Py_XDECREF(GET_TC(tc)->itemValue);
+ if (!GET_TC(tc)->cStr) {
+ return 0;
+ }
+
  if (index == 0) {
- GET_TC(tc)->cStr = "name";
+ strcpy(GET_TC(tc)->cStr, "name");
  GET_TC(tc)->itemValue = PyObject_GetAttrString(obj, "name");
  } else if (index == 1) {
- GET_TC(tc)->cStr = "data";
+ strcpy(GET_TC(tc)->cStr, "data");
  GET_TC(tc)->itemValue = get_values(obj);
  if (!GET_TC(tc)->itemValue) {
  return 0;
@@ -1049,19 +1060,27 @@ static void Series_iterBegin(JSOBJ Py_UNUSED(obj), JSONTypeContext *tc) {
  PyObjectEncoder *enc = (PyObjectEncoder *)tc->encoder;
  GET_TC(tc)->index = 0;
  enc->outputFormat = VALUES; // for contained series
+ GET_TC(tc)->cStr = PyObject_Malloc(CSTR_SIZE);
+ if (!GET_TC(tc)->cStr) {
+ PyErr_NoMemory();
+ }
 }
 
 static int Series_iterNext(JSOBJ obj, JSONTypeContext *tc) {
  const Py_ssize_t index = GET_TC(tc)->index;
  Py_XDECREF(GET_TC(tc)->itemValue);
+ if (!GET_TC(tc)->cStr) {
+ return 0;
+ }
+
  if (index == 0) {
- GET_TC(tc)->cStr = "name";
+ strcpy(GET_TC(tc)->cStr, "name");
  GET_TC(tc)->itemValue = PyObject_GetAttrString(obj, "name");
  } else if (index == 1) {
- GET_TC(tc)->cStr = "index";
+ strcpy(GET_TC(tc)->cStr, "index");
  GET_TC(tc)->itemValue = PyObject_GetAttrString(obj, "index");
  } else if (index == 2) {
- GET_TC(tc)->cStr = "data";
+ strcpy(GET_TC(tc)->cStr, "data");
  GET_TC(tc)->itemValue = get_values(obj);
  if (!GET_TC(tc)->itemValue) {
  return 0;
@@ -1096,19 +1115,27 @@ static void DataFrame_iterBegin(JSOBJ Py_UNUSED(obj), JSONTypeContext *tc) {
  PyObjectEncoder *enc = (PyObjectEncoder *)tc->encoder;
  GET_TC(tc)->index = 0;
  enc->outputFormat = VALUES; // for contained series & index
+ GET_TC(tc)->cStr = PyObject_Malloc(CSTR_SIZE);
+ if (!GET_TC(tc)->cStr) {
+ PyErr_NoMemory();
+ }
 }
 
 static int DataFrame_iterNext(JSOBJ obj, JSONTypeContext *tc) {
  const Py_ssize_t index = GET_TC(tc)->index;
  Py_XDECREF(GET_TC(tc)->itemValue);
+ if (!GET_TC(tc)->cStr) {
+ return 0;
+ }
+
  if (index == 0) {
- GET_TC(tc)->cStr = "columns";
+ strcpy(GET_TC(tc)->cStr, "columns");
  GET_TC(tc)->itemValue = PyObject_GetAttrString(obj, "columns");
  } else if (index == 1) {
- GET_TC(tc)->cStr = "index";
+ strcpy(GET_TC(tc)->cStr, "index");
  GET_TC(tc)->itemValue = PyObject_GetAttrString(obj, "index");
  } else if (index == 2) {
- GET_TC(tc)->cStr = "data";
+ strcpy(GET_TC(tc)->cStr, "data");
  Py_INCREF(obj);
  GET_TC(tc)->itemValue = obj;
  } else {
@@ -1880,6 +1907,7 @@ static void Object_endTypeContext(JSOBJ Py_UNUSED(obj), JSONTypeContext *tc) {
  GET_TC(tc)->rowLabels = NULL;
  NpyArr_freeLabels(GET_TC(tc)->columnLabels, GET_TC(tc)->columnLabelsLen);
  GET_TC(tc)->columnLabels = NULL;
+ PyObject_Free(GET_TC(tc)->cStr);
  GET_TC(tc)->cStr = NULL;
  PyObject_Free(tc->prv);
  tc->prv = NULL;