Fix _PyBytesWriter_Prepare()

Don't call _PyBytesWriter_Dealloc() on error.

Author: vstinner

Objects/bytesobject.c

@@ -2818,8 +2818,9 @@ _PyBytes_FromList(PyObject *x)
 
         if (i >= size) {
             str = _PyBytesWriter_Resize(&writer, str, size+1);
-            if (str == NULL)
-                return NULL;
+            if (str == NULL) {
+                goto error;
+            }
             size = writer.allocated;
         }
         *str++ = (char) value;
@@ -2913,8 +2914,9 @@ _PyBytes_FromIterator(PyObject *it, PyObject *x)
         /* Append the byte */
         if (i >= size) {
             str = _PyBytesWriter_Resize(&writer, str, size+1);
-            if (str == NULL)
-                return NULL;
+            if (str == NULL) {
+                goto error;
+            }
             size = writer.allocated;
         }
         *str++ = (char) value;
@@ -3506,32 +3508,32 @@ PyBytesWriter_CheckPtr(PyBytesWriter *pub_writer, char *str)
 void*
 _PyBytesWriter_Resize(_PyBytesWriter *writer, void *str, Py_ssize_t size)
 {
-    Py_ssize_t allocated, pos;
-
     assert(_PyBytesWriter_CheckConsistency(writer, str));
     assert(writer->allocated < size);
 
-    allocated = size;
+    Py_ssize_t allocated = size;
     if (writer->overallocate
         && allocated <= (PY_SSIZE_T_MAX - allocated / OVERALLOCATE_FACTOR)) {
         /* overallocate to limit the number of realloc() */
         allocated += allocated / OVERALLOCATE_FACTOR;
     }
 
-    pos = _PyBytesWriter_GetSize(writer, str);
+    Py_ssize_t pos = _PyBytesWriter_GetSize(writer, str);
     if (!writer->use_small_buffer) {
         if (writer->use_bytearray) {
-            if (PyByteArray_Resize(writer->buffer, allocated))
-                goto error;
+            if (PyByteArray_Resize(writer->buffer, allocated)) {
+                return NULL;
+            }
             /* writer->allocated can be smaller than writer->buffer->ob_alloc,
                but we cannot use ob_alloc because bytes may need to be moved
                to use the whole buffer. bytearray uses an internal optimization
                to avoid moving or copying bytes when bytes are removed at the
                beginning (ex: del bytearray[:1]). */
         }
         else {
-            if (_PyBytes_Resize(&writer->buffer, allocated))
-                goto error;
+            if (_PyBytes_Resize(&writer->buffer, allocated)) {
+                return NULL;
+            }
         }
     }
     else {
@@ -3542,8 +3544,9 @@ _PyBytesWriter_Resize(_PyBytesWriter *writer, void *str, Py_ssize_t size)
             writer->buffer = PyByteArray_FromStringAndSize(NULL, allocated);
         else
             writer->buffer = PyBytes_FromStringAndSize(NULL, allocated);
-        if (writer->buffer == NULL)
-            goto error;
+        if (writer->buffer == NULL) {
+            return NULL;
+        }
 
         if (pos != 0) {
             char *dest;
@@ -3567,17 +3570,11 @@ _PyBytesWriter_Resize(_PyBytesWriter *writer, void *str, Py_ssize_t size)
     str = _PyBytesWriter_AsString(writer) + pos;
     assert(_PyBytesWriter_CheckConsistency(writer, str));
     return str;
-
-error:
-    _PyBytesWriter_Dealloc(writer);
-    return NULL;
 }
 
 void*
 _PyBytesWriter_Prepare(_PyBytesWriter *writer, void *str, Py_ssize_t size)
 {
-    Py_ssize_t new_min_size;
-
     assert(_PyBytesWriter_CheckConsistency(writer, str));
     assert(size >= 0);
 
@@ -3588,13 +3585,16 @@ _PyBytesWriter_Prepare(_PyBytesWriter *writer, void *str, Py_ssize_t size)
 
     if (writer->min_size > PY_SSIZE_T_MAX - size) {
         PyErr_NoMemory();
-        _PyBytesWriter_Dealloc(writer);
         return NULL;
     }
-    new_min_size = writer->min_size + size;
+    Py_ssize_t new_min_size = writer->min_size + size;
 
-    if (new_min_size > writer->allocated)
+    if (new_min_size > writer->allocated) {
         str = _PyBytesWriter_Resize(writer, str, new_min_size);
+        if (str == NULL) {
+            return NULL;
+        }
+    }
 
     writer->min_size = new_min_size;
     return str;