Avoid zeroing out memory when not required

The only time the internal buffer cleanup code was called was just
before freeing the entire context, so individually zeroing out the
members is pointless. Remove the function entirely and inline the
buffer freeing into the context cleanup codepath.

For zeroing the error buffer, it's only called right after allocating
the error buffer with palloc0() in the first place so the memory will
always be zeroed out when reaching here.
Reviewed-by: NFrancisco Guerrero <aguerrero@pivotal.io>

gpcontrib/pxf/src/libchurl.c

@@ -103,7 +103,6 @@ static void		enlarge_internal_buffer(churl_buffer *buffer, size_t required);
 static void		finish_upload(churl_context *context);
 static void		cleanup_curl_handle(churl_context *context);
 static void		multi_remove_handle(churl_context *context);
-static void		cleanup_internal_buffer(churl_buffer *buffer);
 static void		churl_cleanup_context(churl_context *context);
 static size_t	write_callback(char *buffer, size_t size, size_t nitems, void *userp);
 static void		fill_internal_buffer(churl_context *context, int want);
@@ -111,7 +110,6 @@ static void		churl_headers_set(churl_context *context, CHURL_HEADERS settings);
 static void		check_response_status(churl_context *context);
 static void		check_response_code(churl_context *context);
 static void		check_response(churl_context *context);
-static void		clear_error_buffer(churl_context *context);
 static size_t	header_callback(char *buffer, size_t size, size_t nitems, void *userp);
 static void		free_http_response(churl_context *context);
 static void		compact_internal_buffer(churl_buffer *buffer);
@@ -316,7 +314,6 @@ churl_init(const char *url, CHURL_HEADERS headers)
 	churl_context *context = churl_new_context();
 
 	create_curl_handle(context);
-	clear_error_buffer(context);
 
 /* Required for resolving localhost on some docker environments that
  * had intermittent networking issues when using pxf on HAWQ
@@ -488,8 +485,6 @@ churl_cleanup(CHURL_HANDLE handle, bool after_error)
 	}
 
 	cleanup_curl_handle(context);
-	cleanup_internal_buffer(context->download_buffer);
-	cleanup_internal_buffer(context->upload_buffer);
 	churl_cleanup_context(context);
 }
 
@@ -503,14 +498,6 @@ churl_new_context()
 	return context;
 }
 
-static void
-clear_error_buffer(churl_context *context)
-{
-	if (!context)
-		return;
-	context->curl_error_buffer[0] = 0;
-}
-
 static void
 create_curl_handle(churl_context *context)
 {
@@ -701,28 +688,23 @@ multi_remove_handle(churl_context *context)
 			 curl_error, curl_easy_strerror(curl_error));
 }
 
-static void
-cleanup_internal_buffer(churl_buffer *buffer)
-{
-	if ((buffer) && (buffer->ptr))
-	{
-		pfree(buffer->ptr);
-		buffer->ptr = NULL;
-		buffer->bot = 0;
-		buffer->top = 0;
-		buffer->max = 0;
-	}
-}
-
 static void
 churl_cleanup_context(churl_context *context)
 {
 	if (context)
 	{
 		if (context->download_buffer)
+		{
+			if (context->download_buffer->ptr)
+				pfree(context->download_buffer->ptr);
 			pfree(context->download_buffer);
+		}
 		if (context->upload_buffer)
+		{
+			if (context->upload_buffer->ptr)
+				pfree(context->upload_buffer->ptr);
 			pfree(context->upload_buffer);
+		}
 
 		pfree(context);
 	}