Upstream: https://gitlab.com/free-astro/siril/-/issues/1516
Upstream: https://gitlab.com/free-astro/siril/-/issues/1202
Bug: https://bugs.gentoo.org/957668
--- a/src/core/processing.h
+++ b/src/core/processing.h
@@ -136,6 +136,10 @@ struct generic_seq_args {
 #endif
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gpointer generic_sequence_worker(gpointer p);
 gboolean end_generic_sequence(gpointer p);
 
@@ -184,4 +188,8 @@ gpointer generic_sequence_metadata_worker(gpointer args);
 
 void kill_child_process(gboolean on_exit);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
--- a/src/filters/da3d/DA3D.cpp
+++ b/src/filters/da3d/DA3D.cpp
@@ -15,10 +15,8 @@
 #include "WeightMap.hpp"
 #include "Utils.hpp"
 #include "DftPatch.hpp"
-extern "C" {
 #include "core/processing.h"
 #include "gui/progress_and_log.h"
-}
 
 #ifdef _OPENMP
 #include <omp.h>
--- a/src/filters/nlbayes/NlBayes.cpp
+++ b/src/filters/nlbayes/NlBayes.cpp
@@ -27,11 +27,9 @@
 #include "LibMatrix.h"
 #include "LibImages.h"
 #include "Utilities.h"
-extern "C" {
 #include "algos/anscombe.h"
 #include "core/processing.h"
 #include "gui/progress_and_log.h"
-}
 
 #ifdef _OPENMP
 #include <omp.h>
--- a/src/gui/progress_and_log.h
+++ b/src/gui/progress_and_log.h
@@ -10,6 +10,10 @@
 #define PROGRESS_DONE 1.0		// fill the progress bar
 #define PROGRESS_TEXT_RESET ""		// reset the progress bar's text
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void initialize_log_tags();
 void gui_log_message(const char* msg, const char* color);
 
@@ -17,4 +21,8 @@ void set_progress_bar_data(const char *text, double percent);
 void set_cursor_waiting(gboolean waiting);
 void set_cursor(const gchar* cursor_name);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
--- a/src/opencv/opencv.h
+++ b/src/opencv/opencv.h
@@ -5,14 +5,15 @@
 #  include <config.h>
 #endif
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <stdint.h>
 #include "registration/registration.h"
 #include "registration/matching/misc.h"
 #include "registration/matching/atpmatch.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "gui/progress_and_log.h"
 
 WORD *fits_to_bgrbgr_ushort(fits *image);