Add guard defines

Author: AA-Turner

Modules/_zstd/_zstdmodule.h

@@ -1,11 +1,12 @@
-#pragma once
 /*
 Low level interface to Meta's zstd library for use in the compression.zstd
 Python module.
 */
 
 /* Declarations shared between different parts of the _zstd module*/
 
+#ifndef ZSTD_MODULE_H
+#define ZSTD_MODULE_H
 #include "Python.h"
 
 #include "zstd.h"
@@ -154,3 +155,5 @@ set_zstd_error(const _zstd_state* const state,
 extern void
 set_parameter_error(const _zstd_state* const state, int is_compress,
                     int key_v, int value_v);
+
+#endif

Modules/_zstd/buffer.h

@@ -3,7 +3,10 @@ Low level interface to Meta's zstd library for use in the compression.zstd
 Python module.
 */
 
+#ifndef ZSTD_BUFFER_H
+#define ZSTD_BUFFER_H
 #include "_zstdmodule.h"
+#include "Python.h"
 #include "pycore_blocks_output_buffer.h"
 
 /* Blocks output buffer wrapper code */
@@ -102,3 +105,5 @@ _OutputBuffer_ReachedMaxLength(_BlocksOutputBuffer *buffer, ZSTD_outBuffer *ob)
 
     return buffer->allocated == buffer->max_length;
 }
+
+#endif