diff --git a/build_files/cmake/have_features.cmake b/build_files/cmake/have_features.cmake
index de90d7fcdd2..c6bb0884a8c 100644
--- a/build_files/cmake/have_features.cmake
+++ b/build_files/cmake/have_features.cmake
@@ -8,7 +8,7 @@
 
 include(CheckSymbolExists)
 
-# Used for: `intern/guardedalloc/intern/mallocn_intern.h`.
+# Used for: `intern/guardedalloc/intern/mallocn_intern.hh`.
 # Function `malloc_stats` is only available on GLIBC,
 # so check that before defining `HAVE_MALLOC_STATS`.
 check_symbol_exists(malloc_stats "malloc.h" HAVE_MALLOC_STATS_H)
diff --git a/intern/guardedalloc/CMakeLists.txt b/intern/guardedalloc/CMakeLists.txt
index b2db54c0e6e..d622adab486 100644
--- a/intern/guardedalloc/CMakeLists.txt
+++ b/intern/guardedalloc/CMakeLists.txt
@@ -26,8 +26,8 @@ set(SRC
   ./intern/memory_usage.cc
 
   MEM_guardedalloc.h
-  ./intern/mallocn_inline.h
-  ./intern/mallocn_intern.h
+  ./intern/mallocn_inline.hh
+  ./intern/mallocn_intern.hh
 
   # only so the header is known by cmake
   ../atomic/atomic_ops.h
diff --git a/intern/guardedalloc/intern/leak_detector.cc b/intern/guardedalloc/intern/leak_detector.cc
index 091b5dffe2e..f4895d182ca 100644
--- a/intern/guardedalloc/intern/leak_detector.cc
+++ b/intern/guardedalloc/intern/leak_detector.cc
@@ -10,7 +10,7 @@
 #include <cstdlib>
 
 #include "MEM_guardedalloc.h"
-#include "mallocn_intern.h"
+#include "mallocn_intern.hh"
 
 bool leak_detector_has_run = false;
 char free_after_leak_detection_message[] =
diff --git a/intern/guardedalloc/intern/mallocn.cc b/intern/guardedalloc/intern/mallocn.cc
index 7fcd708f45c..a331d39b658 100644
--- a/intern/guardedalloc/intern/mallocn.cc
+++ b/intern/guardedalloc/intern/mallocn.cc
@@ -15,7 +15,7 @@
 
 #include <cassert>
 
-#include "mallocn_intern.h"
+#include "mallocn_intern.hh"
 
 #ifdef WITH_JEMALLOC_CONF
 /**
diff --git a/intern/guardedalloc/intern/mallocn_guarded_impl.cc b/intern/guardedalloc/intern/mallocn_guarded_impl.cc
index 6cb93544772..74ab255adef 100644
--- a/intern/guardedalloc/intern/mallocn_guarded_impl.cc
+++ b/intern/guardedalloc/intern/mallocn_guarded_impl.cc
@@ -29,7 +29,7 @@
 #include "../../source/blender/blenlib/BLI_strict_flags.h"
 
 #include "atomic_ops.h"
-#include "mallocn_intern.h"
+#include "mallocn_intern.hh"
 
 /* Only for debugging:
  * store original buffer's name when doing MEM_dupallocN
diff --git a/intern/guardedalloc/intern/mallocn_inline.h b/intern/guardedalloc/intern/mallocn_inline.hh
similarity index 85%
rename from intern/guardedalloc/intern/mallocn_inline.h
rename to intern/guardedalloc/intern/mallocn_inline.hh
index 9ecbc3d03e9..27abaee4b32 100644
--- a/intern/guardedalloc/intern/mallocn_inline.h
+++ b/intern/guardedalloc/intern/mallocn_inline.hh
@@ -3,18 +3,12 @@
  * SPDX-FileCopyrightText: 2009-2017 Facebook, Inc. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-2-Clause */
+#pragma once
 
 /** \file
  * \ingroup intern_mem
  */
 
-#ifndef __MALLOCN_INLINE_H__
-#define __MALLOCN_INLINE_H__
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 MEM_INLINE bool MEM_size_safe_multiply(size_t a, size_t b, size_t *result)
 {
   /* A size_t with its high-half bits all set to 1. */
@@ -33,9 +27,3 @@ MEM_INLINE bool MEM_size_safe_multiply(size_t a, size_t b, size_t *result)
    */
   return ((high_bits & (a | b)) == 0 || (*result / b == a));
 }
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* __MALLOCN_INLINE_H__ */
diff --git a/intern/guardedalloc/intern/mallocn_intern.h b/intern/guardedalloc/intern/mallocn_intern.hh
similarity index 97%
rename from intern/guardedalloc/intern/mallocn_intern.h
rename to intern/guardedalloc/intern/mallocn_intern.hh
index 32e31aafb29..92ff8d0f8dc 100644
--- a/intern/guardedalloc/intern/mallocn_intern.h
+++ b/intern/guardedalloc/intern/mallocn_intern.hh
@@ -1,14 +1,12 @@
 /* SPDX-FileCopyrightText: 2013 Blender Authors
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
+#pragma once
 
 /** \file
  * \ingroup intern_mem
  */
 
-#ifndef __MALLOCN_INTERN_H__
-#define __MALLOCN_INTERN_H__
-
 #ifdef __GNUC__
 #  define UNUSED(x) UNUSED_##x __attribute__((__unused__))
 #elif defined(_MSC_VER)
@@ -95,11 +93,7 @@ size_t malloc_usable_size(void *ptr);
 /* Real pointer returned by the malloc or aligned_alloc. */
 #define MEMHEAD_REAL_PTR(memh) ((char *)memh - MEMHEAD_ALIGN_PADDING(memh->alignment))
 
-#include "mallocn_inline.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
+#include "mallocn_inline.hh"
 
 #define ALIGNED_MALLOC_MINIMUM_ALIGNMENT sizeof(void *)
 
@@ -227,9 +221,3 @@ void mem_guarded_clearmemlist(void);
 const char *MEM_guarded_name_ptr(void *vmemh);
 void MEM_guarded_name_ptr_set(void *vmemh, const char *str);
 #endif
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* __MALLOCN_INTERN_H__ */
diff --git a/intern/guardedalloc/intern/mallocn_lockfree_impl.cc b/intern/guardedalloc/intern/mallocn_lockfree_impl.cc
index 571d08c4f97..e2197ab1d83 100644
--- a/intern/guardedalloc/intern/mallocn_lockfree_impl.cc
+++ b/intern/guardedalloc/intern/mallocn_lockfree_impl.cc
@@ -26,7 +26,7 @@
 #include "../../source/blender/blenlib/BLI_strict_flags.h"
 
 #include "atomic_ops.h"
-#include "mallocn_intern.h"
+#include "mallocn_intern.hh"
 
 typedef struct MemHead {
   /* Length of allocated memory block. */
diff --git a/intern/guardedalloc/intern/memory_usage.cc b/intern/guardedalloc/intern/memory_usage.cc
index a858613e715..ca7ad91d680 100644
--- a/intern/guardedalloc/intern/memory_usage.cc
+++ b/intern/guardedalloc/intern/memory_usage.cc
@@ -11,7 +11,7 @@
 #include <vector>
 
 #include "MEM_guardedalloc.h"
-#include "mallocn_intern.h"
+#include "mallocn_intern.hh"
 
 #include "../../source/blender/blenlib/BLI_strict_flags.h"