diff --git a/gnucash/gnome-utils/gnc-main-window.h b/gnucash/gnome-utils/gnc-main-window.h
index ba5284e40b..7216fc3e08 100644
--- a/gnucash/gnome-utils/gnc-main-window.h
+++ b/gnucash/gnome-utils/gnc-main-window.h
@@ -35,14 +35,15 @@
 
 #ifndef __GNC_MAIN_WINDOW_H
 #define __GNC_MAIN_WINDOW_H
+
+#include <gtk/gtk.h>
+#include "gnc-plugin-page.h"
+
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-#include <gtk/gtk.h>
-#include "gnc-plugin-page.h"
-
 /* type macros */
 #define GNC_TYPE_MAIN_WINDOW            (gnc_main_window_get_type ())
 #define GNC_MAIN_WINDOW(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GNC_TYPE_MAIN_WINDOW, GncMainWindow))
diff --git a/gnucash/gnome-utils/gnc-report-combo.h b/gnucash/gnome-utils/gnc-report-combo.h
index e71566405f..cc2b0792e1 100644
--- a/gnucash/gnome-utils/gnc-report-combo.h
+++ b/gnucash/gnome-utils/gnc-report-combo.h
@@ -51,6 +51,11 @@ typedef struct
     char *report_name;
 } ReportListEntry;
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /** Return the GType for the GncReportCombo widget.
  *
  *  @return A GType value.
@@ -128,4 +133,8 @@ gchar * gnc_report_combo_get_active_guid_name (GncReportCombo *grc);
  */
 gboolean gnc_report_combo_is_warning_visible_for_active (GncReportCombo *grc);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* __GNC_REPORT_COMBO_H__ */
diff --git a/gnucash/gnome/business-options-gnome.cpp b/gnucash/gnome/business-options-gnome.cpp
index f8155ab779..e28c667f1d 100644
--- a/gnucash/gnome/business-options-gnome.cpp
+++ b/gnucash/gnome/business-options-gnome.cpp
@@ -33,10 +33,7 @@
 #include <gnc-general-search.h> // for GNC_GENERAL_SEARCH
 #include "dialog-utils.h" // for gnc_builder_add_from_file
 
-extern "C"
-{
 #include "gnc-report-combo.h"
-}
 
 #include <iostream>
 #include <sstream>
diff --git a/gnucash/gnome/dialog-new-user.h b/gnucash/gnome/dialog-new-user.h
index b92ade6b81..78fab780fa 100644
--- a/gnucash/gnome/dialog-new-user.h
+++ b/gnucash/gnome/dialog-new-user.h
@@ -23,6 +23,8 @@
 #ifndef DIALOG_NEW_USER_H
 #define DIALOG_NEW_USER_H
 
+#include <glib.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -30,8 +32,6 @@ extern "C" {
 #define GNC_PREFS_GROUP_NEW_USER "dialogs.new-user"
 #define GNC_PREF_FIRST_STARTUP "first-startup"
 
-#include <glib.h>
-
 typedef struct _GNCNewUserDialog GNCNewUserDialog;
 
 void gnc_ui_new_user_dialog (void);
diff --git a/gnucash/gnome/gnc-plugin-page-report.h b/gnucash/gnome/gnc-plugin-page-report.h
index 46ba3ca507..9e1b914a56 100644
--- a/gnucash/gnome/gnc-plugin-page-report.h
+++ b/gnucash/gnome/gnc-plugin-page-report.h
@@ -34,16 +34,14 @@
 #ifndef __GNC_PLUGIN_PAGE_REPORT_H
 #define __GNC_PLUGIN_PAGE_REPORT_H
 
+#include <gtk/gtk.h>
+#include "gnc-plugin.h"
+
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-#include <gtk/gtk.h>
-#include "gnc-plugin.h"
-
-G_BEGIN_DECLS
-
 /* type macros */
 #define GNC_TYPE_PLUGIN_PAGE_REPORT            (gnc_plugin_page_report_get_type ())
 #define GNC_PLUGIN_PAGE_REPORT(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GNC_TYPE_PLUGIN_PAGE_REPORT, GncPluginPageReport))
@@ -89,10 +87,10 @@ void       gnc_main_window_open_report (int report_id, GncMainWindow *window);
 // directly called through from above
 void       gnc_main_window_open_report_url (const char * url, GncMainWindow *window);
 
-G_END_DECLS
 #ifdef __cplusplus
 }
 #endif
+
 #endif /* __GNC_PLUGIN_PAGE_REPORT_H */
 /** @} */
 /** @} */
diff --git a/gnucash/gnome/window-report.h b/gnucash/gnome/window-report.h
index d21ef6aca8..30362254af 100644
--- a/gnucash/gnome/window-report.h
+++ b/gnucash/gnome/window-report.h
@@ -24,16 +24,16 @@
 #define GNC_REPORT_WINDOW_H
 
 #include <libguile.h>
-#ifdef __cplusplus
-extern "C"
-{
-#endif
 //#include "gnc-html.h"
 #include "qof.h"
 #include "gnc-optiondb.h"
 
 typedef struct gnc_report_window_s gnc_report_window;
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 /** PROTOTYPES ******************************************************/
 
 // scm-exposed
diff --git a/gnucash/gnucash-locale-macos.mm b/gnucash/gnucash-locale-macos.mm
index dc33b596c0..80ca5b3311 100644
--- a/gnucash/gnucash-locale-macos.mm
+++ b/gnucash/gnucash-locale-macos.mm
@@ -28,10 +28,8 @@
 #include <qoflog.h>
 #include <gnc-engine.h>
 
-extern "C" {
 #include <gnc-locale-utils.h>
 #include "gnucash-locale-platform.h"
-}
 
 /* This static indicates the debugging module that this .o belongs to.  */
 static QofLogModule log_module = GNC_MOD_GUI;
diff --git a/gnucash/import-export/import-backend.cpp b/gnucash/import-export/import-backend.cpp
index e4a81b8a61..df80be0965 100644
--- a/gnucash/import-export/import-backend.cpp
+++ b/gnucash/import-export/import-backend.cpp
@@ -35,7 +35,6 @@
 
 #include <errno.h>
 
-extern "C" {
 #include "import-backend.h"
 #include "import-utilities.h"
 #include "Account.h"
@@ -44,7 +43,6 @@ extern "C" {
 #include "engine-helpers.h"
 #include "gnc-prefs.h"
 #include "gnc-ui-util.h"
-}
 
 #include <algorithm>
 
diff --git a/gnucash/import-export/import-main-matcher.h b/gnucash/import-export/import-main-matcher.h
index 8320e3a6f2..1c75a47a3d 100644
--- a/gnucash/import-export/import-main-matcher.h
+++ b/gnucash/import-export/import-main-matcher.h
@@ -36,12 +36,12 @@
 #include "Transaction.h"
 #include "import-backend.h"
 
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <stdbool.h>
-
 typedef struct _main_matcher_info GNCImportMainMatcher;
 
 typedef void (*GNCTransactionProcessedCB) (GNCImportTransInfo *trans_info,
diff --git a/gnucash/import-export/import-settings.h b/gnucash/import-export/import-settings.h
index 133699bcaf..8c7fd67fe4 100644
--- a/gnucash/import-export/import-settings.h
+++ b/gnucash/import-export/import-settings.h
@@ -30,6 +30,11 @@
 
 #include "import-utilities.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 typedef struct _genimportsettings GNCImportSettings;
 
 /************************************************************************
@@ -103,6 +108,11 @@ void gnc_import_Settings_set_match_date_hardlimit (GNCImportSettings *settings,
 gint gnc_import_Settings_get_match_date_hardlimit (const GNCImportSettings *settings);
 
 /**@}*/
+
+#ifdef __cplusplus
+}
+#endif
+
 /**@}*/
 
 #endif
diff --git a/gnucash/import-export/import-utilities.h b/gnucash/import-export/import-utilities.h
index 204643bf64..3f20886a6d 100644
--- a/gnucash/import-export/import-utilities.h
+++ b/gnucash/import-export/import-utilities.h
@@ -40,6 +40,11 @@
 
 #include "Account.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /** @name Setter-getters
     Setter and getter functions for the online_id field for
     Accounts.
@@ -73,6 +78,10 @@ void gnc_import_set_split_online_id(Split * split,
 
 gboolean gnc_import_split_has_online_id(Split * split);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
 /** @} */
 
diff --git a/libgnucash/app-utils/mocks/gmock-gnc-prefs.h b/libgnucash/app-utils/mocks/gmock-gnc-prefs.h
index 56da9e6c44..2ea6abb516 100644
--- a/libgnucash/app-utils/mocks/gmock-gnc-prefs.h
+++ b/libgnucash/app-utils/mocks/gmock-gnc-prefs.h
@@ -3,10 +3,7 @@
 
 #include <gmock/gmock.h>
 
-extern "C"
-{
 #include <gnc-prefs.h>
-}
 
 
 // mock up class implementing preferences backend (see struct PrefBackend in gnc-prefs-p.h)
diff --git a/libgnucash/backend/dbi/gnc-backend-dbi.h b/libgnucash/backend/dbi/gnc-backend-dbi.h
index 1c53d03fba..78ccbef473 100644
--- a/libgnucash/backend/dbi/gnc-backend-dbi.h
+++ b/libgnucash/backend/dbi/gnc-backend-dbi.h
@@ -28,10 +28,11 @@
 
 #ifndef GNC_BACKEND_DBI_H_
 #define GNC_BACKEND_DBI_H_
-extern "C"
-{
+
 #include <gmodule.h>
 
+extern "C"
+{
 /** Initialization function which can be used when this module is
  * statically linked into the application. */
 void gnc_module_init_backend_dbi (void);
diff --git a/libgnucash/backend/dbi/test/test-dbi-stuff.h b/libgnucash/backend/dbi/test/test-dbi-stuff.h
index 81f3fe1d42..5b128145a5 100644
--- a/libgnucash/backend/dbi/test/test-dbi-stuff.h
+++ b/libgnucash/backend/dbi/test/test-dbi-stuff.h
@@ -25,10 +25,6 @@
 
 #ifndef _TEST_DBI_STUFF_H_
 #define _TEST_DBI_STUFF_H_
-#ifdef __cplusplus
-extern "C"
-{
-#endif
 #include "qof.h"
 
 typedef struct
@@ -37,10 +33,17 @@ typedef struct
     QofBook* book_2;
     gboolean result;
 } CompareInfoStruct;
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 void compare_books (QofBook* book_1, QofBook* book_2);
 
 void do_compare (QofBook* book_1, QofBook* book_2, const gchar* id,
                  QofInstanceForeachCB cb, const gchar* msg);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libgnucash/backend/sql/gnc-commodity-sql.h b/libgnucash/backend/sql/gnc-commodity-sql.h
index ba32b3f363..559b25e54d 100644
--- a/libgnucash/backend/sql/gnc-commodity-sql.h
+++ b/libgnucash/backend/sql/gnc-commodity-sql.h
@@ -32,10 +32,7 @@
 #include "gnc-sql-backend.hpp"
 #include "gnc-sql-object-backend.hpp"
 
-extern "C"
-{
 #include "gnc-commodity.h"
-}
 
 class GncSqlCommodityBackend : public GncSqlObjectBackend
 {
diff --git a/libgnucash/backend/sql/gnc-recurrence-sql.h b/libgnucash/backend/sql/gnc-recurrence-sql.h
index a29a97fb02..23f8e82a66 100644
--- a/libgnucash/backend/sql/gnc-recurrence-sql.h
+++ b/libgnucash/backend/sql/gnc-recurrence-sql.h
@@ -28,12 +28,11 @@
 
 #ifndef GNC_RECURRENCE_SQL_H
 #define GNC_RECURRENCE_SQL_H
-extern "C"
-{
+
 #include <glib.h>
+
 #include "Recurrence.h"
 #include "guid.h"
-}
 #include "gnc-sql-object-backend.hpp"
 
 class GncSqlRecurrenceBackend : public GncSqlObjectBackend
diff --git a/libgnucash/backend/sql/gnc-schedxaction-sql.h b/libgnucash/backend/sql/gnc-schedxaction-sql.h
index 848180dd70..0fa4f8ffb9 100644
--- a/libgnucash/backend/sql/gnc-schedxaction-sql.h
+++ b/libgnucash/backend/sql/gnc-schedxaction-sql.h
@@ -28,10 +28,8 @@
 
 #ifndef GNC_SCHEDXACTION_SQL_H
 #define GNC_SCHEDXACTION_SQL_H
-extern "C"
-{
+
 #include "qof.h"
-}
 #include "gnc-sql-object-backend.hpp"
 
 class GncSqlSchedXactionBackend : public GncSqlObjectBackend
diff --git a/libgnucash/backend/sql/gnc-slots-sql.h b/libgnucash/backend/sql/gnc-slots-sql.h
index b7b9891537..49d162b2ce 100644
--- a/libgnucash/backend/sql/gnc-slots-sql.h
+++ b/libgnucash/backend/sql/gnc-slots-sql.h
@@ -28,12 +28,10 @@
 
 #ifndef GNC_SLOTS_SQL_H
 #define GNC_SLOTS_SQL_H
-extern "C"
-{
+
 #include <glib.h>
 #include "guid.h"
 #include "qof.h"
-}
 #include "gnc-sql-object-backend.hpp"
 
 /**
diff --git a/libgnucash/backend/sql/gnc-transaction-sql.h b/libgnucash/backend/sql/gnc-transaction-sql.h
index 78d35b2c0e..8aac7f8b57 100644
--- a/libgnucash/backend/sql/gnc-transaction-sql.h
+++ b/libgnucash/backend/sql/gnc-transaction-sql.h
@@ -29,12 +29,10 @@
 #ifndef GNC_TRANSACTION_SQL_H
 #define GNC_TRANSACTION_SQL_H
 
-extern "C"
-{
 #include "Transaction.h"
 #include "qof.h"
 #include "Account.h"
-}
+
 class GncSqlTransBackend : public GncSqlObjectBackend
 {
 public:
diff --git a/libgnucash/backend/xml/gnc-backend-xml.h b/libgnucash/backend/xml/gnc-backend-xml.h
index a3aa1a09bd..aaaac5ea4d 100644
--- a/libgnucash/backend/xml/gnc-backend-xml.h
+++ b/libgnucash/backend/xml/gnc-backend-xml.h
@@ -30,10 +30,7 @@
 
 #ifndef GNC_BACKEND_XML_H_
 #define GNC_BACKEND_XML_H_
-#ifdef __cplusplus
-extern "C"
-{
-#endif
+
 #include <qof.h>
 #include <gmodule.h>
 
@@ -55,6 +52,10 @@ typedef enum
     GNC_BOOK_POST_XML2_0_0_FILE
 } QofBookFileType;
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 /** Initialization function which can be used when this module is
  * statically linked into the application. */
 void gnc_module_init_backend_xml (void);
diff --git a/libgnucash/backend/xml/gnc-bill-term-xml-v2.h b/libgnucash/backend/xml/gnc-bill-term-xml-v2.h
index 8c007763c0..de6eacb59c 100644
--- a/libgnucash/backend/xml/gnc-bill-term-xml-v2.h
+++ b/libgnucash/backend/xml/gnc-bill-term-xml-v2.h
@@ -23,10 +23,7 @@
 
 #ifndef GNC_BILLTERM_XML_V2_H
 #define GNC_BILLTERM_XML_V2_H
-extern "C"
-{
 #include "gncBillTerm.h"
-}
 
 void gnc_billterm_xml_initialize (void);
 GncBillTerm* gnc_billterm_xml_find_or_create (QofBook* book, GncGUID* guid);
diff --git a/libgnucash/backend/xml/gnc-owner-xml-v2.h b/libgnucash/backend/xml/gnc-owner-xml-v2.h
index 1b956a2b70..a68a633b64 100644
--- a/libgnucash/backend/xml/gnc-owner-xml-v2.h
+++ b/libgnucash/backend/xml/gnc-owner-xml-v2.h
@@ -22,11 +22,8 @@
 
 #ifndef GNC_OWNER_XML_V2_H
 #define GNC_OWNER_XML_V2_H
-extern "C"
-{
 #include "gncOwner.h"
 #include "qof.h"
-}
 gboolean   gnc_dom_tree_to_owner (xmlNodePtr node, GncOwner* owner,
                                   QofBook* book);
 xmlNodePtr gnc_owner_to_dom_tree (const char* tag, const GncOwner* addr);
diff --git a/libgnucash/backend/xml/gnc-xml-helper.h b/libgnucash/backend/xml/gnc-xml-helper.h
index 6c0f91d8d4..b508c1ce68 100644
--- a/libgnucash/backend/xml/gnc-xml-helper.h
+++ b/libgnucash/backend/xml/gnc-xml-helper.h
@@ -27,8 +27,6 @@
 
 #include <glib.h>
 
-extern "C"
-{
 #include <libxml/xmlversion.h>
 
 #  include <libxml/SAX.h>
@@ -36,7 +34,7 @@ extern "C"
 #  include <libxml/parser.h>
 #  include <libxml/xmlmemory.h>
 #  include <libxml/parserInternals.h>
-}
+
 #  ifndef xmlChildrenNode
 #    define xmlChildrenNode children
 #  endif /* ifndef xmlChildrenNode */
diff --git a/libgnucash/backend/xml/gnc-xml.h b/libgnucash/backend/xml/gnc-xml.h
index 164a124810..b51ff08377 100644
--- a/libgnucash/backend/xml/gnc-xml.h
+++ b/libgnucash/backend/xml/gnc-xml.h
@@ -25,13 +25,10 @@
 #ifndef GNC_XML_H
 #define GNC_XML_H
 
-extern "C"
-{
 #include "SchedXaction.h"
 #include "gnc-engine.h"
 #include "gnc-pricedb.h"
 #include "gnc-budget.h"
-}
 
 #include "gnc-xml-helper.h"
 #include "sixtp.h"
diff --git a/libgnucash/backend/xml/io-example-account.h b/libgnucash/backend/xml/io-example-account.h
index 3924ca2714..b72fb55799 100644
--- a/libgnucash/backend/xml/io-example-account.h
+++ b/libgnucash/backend/xml/io-example-account.h
@@ -24,10 +24,6 @@
 
 #ifndef IO_EXAMPLE_ACCOUNT_H
 #define IO_EXAMPLE_ACCOUNT_H
-#ifdef __cplusplus
-extern "C"
-{
-#endif
 #include <glib.h>
 
 #include "gnc-engine.h"
@@ -45,6 +41,10 @@ struct GncExampleAccount_struct
 };
 typedef struct GncExampleAccount_struct GncExampleAccount;
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 void gnc_destroy_example_account (GncExampleAccount* gea);
 
 gboolean gnc_write_example_account (GncExampleAccount* gea,
diff --git a/libgnucash/backend/xml/io-gncxml-v2.h b/libgnucash/backend/xml/io-gncxml-v2.h
index ccfb4b3a0b..26647a51f6 100644
--- a/libgnucash/backend/xml/io-gncxml-v2.h
+++ b/libgnucash/backend/xml/io-gncxml-v2.h
@@ -30,15 +30,12 @@
 
 #ifndef IO_GNCXML_V2_H
 #define IO_GNCXML_V2_H
-#ifdef __cplusplus
-extern "C"
-{
-#endif
+
 #include <glib.h>
 
 #include "gnc-engine.h"
+
 #ifdef __cplusplus
-}
 #include "gnc-backend-xml.h"
 #include "sixtp.h"
 #include <vector>
diff --git a/libgnucash/backend/xml/io-gncxml.h b/libgnucash/backend/xml/io-gncxml.h
index 1ee52128af..24a8fb1a39 100644
--- a/libgnucash/backend/xml/io-gncxml.h
+++ b/libgnucash/backend/xml/io-gncxml.h
@@ -32,14 +32,15 @@
 
 #ifndef IO_GNCXML_H
 #define IO_GNCXML_H
-#ifdef __cplusplus
-extern "C"
-{
-#endif
 
 #include <glib.h>
 #include "qof.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+
+#endif
 /* FIXME: eventually, we probably need to add an error stack
    accessible via gnc_book_get_xml_io_error() a la binfile. */
 
diff --git a/libgnucash/backend/xml/io-utils.h b/libgnucash/backend/xml/io-utils.h
index c6a4ba4421..cda12393bd 100644
--- a/libgnucash/backend/xml/io-utils.h
+++ b/libgnucash/backend/xml/io-utils.h
@@ -24,11 +24,8 @@
 
 #ifndef IO_UTILS_H
 #define IO_UTILS_H
-extern "C"
-{
 #include <stdio.h>
 #include "qof.h"
-}
 
 #include "io-gncxml-v2.h"
 
diff --git a/libgnucash/backend/xml/sixtp-dom-generators.h b/libgnucash/backend/xml/sixtp-dom-generators.h
index daf5bacd53..79c13f505a 100644
--- a/libgnucash/backend/xml/sixtp-dom-generators.h
+++ b/libgnucash/backend/xml/sixtp-dom-generators.h
@@ -24,14 +24,11 @@
 #ifndef SIXTP_DOM_GENERATORS_H
 #define SIXTP_DOM_GENERATORS_H
 
-extern "C"
-{
 #include <glib.h>
 
 #include "gnc-commodity.h"
 #include "qof.h"
 #include "Recurrence.h"
-}
 
 #include "gnc-xml-helper.h"
 
diff --git a/libgnucash/backend/xml/sixtp-dom-parsers.h b/libgnucash/backend/xml/sixtp-dom-parsers.h
index c630296507..cc1d2544dc 100644
--- a/libgnucash/backend/xml/sixtp-dom-parsers.h
+++ b/libgnucash/backend/xml/sixtp-dom-parsers.h
@@ -23,14 +23,11 @@
 
 #ifndef SIXTP_DOM_PARSERS_H
 #define SIXTP_DOM_PARSERS_H
-extern "C"
-{
 #include <glib.h>
 
 #include "gnc-commodity.h"
 #include "qof.h"
 #include "gnc-budget.h"
-}
 
 #include "gnc-xml-helper.h"
 
diff --git a/libgnucash/backend/xml/sixtp-stack.h b/libgnucash/backend/xml/sixtp-stack.h
index 3803afd895..ab487ffa02 100644
--- a/libgnucash/backend/xml/sixtp-stack.h
+++ b/libgnucash/backend/xml/sixtp-stack.h
@@ -23,10 +23,7 @@
 
 #ifndef SIXTP_STACK_H
 #define SIXTP_STACK_H
-extern "C"
-{
 #include <glib.h>
-}
 
 #include "sixtp.h"
 
diff --git a/libgnucash/backend/xml/sixtp-utils.h b/libgnucash/backend/xml/sixtp-utils.h
index 2ee7aa16ae..ef7b0f03f0 100644
--- a/libgnucash/backend/xml/sixtp-utils.h
+++ b/libgnucash/backend/xml/sixtp-utils.h
@@ -23,10 +23,7 @@
 
 #ifndef SIXTP_UTILS_H
 #define SIXTP_UTILS_H
-extern "C"
-{
 #include "qof.h"
-}
 #include "sixtp.h"
 
 typedef struct
diff --git a/libgnucash/backend/xml/sixtp.h b/libgnucash/backend/xml/sixtp.h
index 82d6e8f5d3..15e61595e4 100644
--- a/libgnucash/backend/xml/sixtp.h
+++ b/libgnucash/backend/xml/sixtp.h
@@ -26,13 +26,10 @@
 
 #include <glib.h>
 
-extern "C"
-{
 #include <stdio.h>
 
 #include <stdarg.h>
 #include "gnc-engine.h"
-}
 
 #include "gnc-xml-helper.h"
 #include "gnc-backend-xml.h"
diff --git a/libgnucash/backend/xml/test/test-dom-parser1.cpp b/libgnucash/backend/xml/test/test-dom-parser1.cpp
index 28de9542cb..7c2923f102 100644
--- a/libgnucash/backend/xml/test/test-dom-parser1.cpp
+++ b/libgnucash/backend/xml/test/test-dom-parser1.cpp
@@ -19,14 +19,11 @@
 \********************************************************************/
 #include <glib.h>
 
-extern "C"
-{
 #include <config.h>
 
 #include <string.h>
 
 #include "test-stuff.h"
-}
 
 #include <cstdlib>
 
diff --git a/libgnucash/backend/xml/test/test-file-stuff.h b/libgnucash/backend/xml/test/test-file-stuff.h
index 158d8cddf3..c73168b0d0 100644
--- a/libgnucash/backend/xml/test/test-file-stuff.h
+++ b/libgnucash/backend/xml/test/test-file-stuff.h
@@ -26,11 +26,8 @@
 #define TEST_FILE_STUFF_H
 #include <glib.h>
 
-extern "C"
-{
 #include <gnc-commodity.h>
 #include <gnc-engine.h>
-}
 #include <gnc-xml-helper.h>
 #include <io-gncxml-gen.h>
 #include <sixtp.h>
diff --git a/libgnucash/backend/xml/test/test-save-in-lang.cpp b/libgnucash/backend/xml/test/test-save-in-lang.cpp
index 78cc644b6b..00acb770bd 100644
--- a/libgnucash/backend/xml/test/test-save-in-lang.cpp
+++ b/libgnucash/backend/xml/test/test-save-in-lang.cpp
@@ -20,8 +20,6 @@
 #include <glib.h>
 #include <glib/gstdio.h>
 
-extern "C"
-{
 #include <config.h>
 #include <unistd.h>
 #include <sys/types.h>
@@ -34,7 +32,6 @@ extern "C"
 
 #include "gnc-engine.h"
 #include "TransLog.h"
-}
 
 #include <cstdlib>
 
diff --git a/libgnucash/core-utils/gnc-locale-utils.h b/libgnucash/core-utils/gnc-locale-utils.h
index b87f3b7406..6683481765 100644
--- a/libgnucash/core-utils/gnc-locale-utils.h
+++ b/libgnucash/core-utils/gnc-locale-utils.h
@@ -25,6 +25,11 @@
 #include <glib.h>
 #include <locale.h>
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /* The gnc_localeconv() subroutine returns an lconv structure
  * containing locale information. If no locale is set, the structure
  * is given default (en_US) values.  */
@@ -41,4 +46,8 @@ int gnc_locale_decimal_places (void);
  * The returned string should be freed by the caller. */
 gchar *gnc_locale_name (void);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_LOCALE_UTILS_H */
diff --git a/libgnucash/engine/gnc-aqbanking-templates.h b/libgnucash/engine/gnc-aqbanking-templates.h
index 9350d5c3b6..ea95b298e2 100644
--- a/libgnucash/engine/gnc-aqbanking-templates.h
+++ b/libgnucash/engine/gnc-aqbanking-templates.h
@@ -33,16 +33,14 @@
 #ifndef GNC_AB_TRANS_TEMPL_H
 #define GNC_AB_TRANS_TEMPL_H
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 #include <config.h>
 #include <glib.h>
 #include "qof.h"
 
-G_BEGIN_DECLS
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 
 /** A template for an AqBanking transaction */
 typedef struct _GncABTransTempl GncABTransTempl;
@@ -204,7 +202,6 @@ void gnc_ab_trans_templ_set_purpose(GncABTransTempl *t, const gchar *purpose);
 void gnc_ab_trans_templ_set_purpose_cont(GncABTransTempl *t,
         const gchar *purpose_cont);
 
-G_END_DECLS
 #ifdef __cplusplus
 }
 #endif
diff --git a/libgnucash/engine/gnc-budget.h b/libgnucash/engine/gnc-budget.h
index eee615303d..58d4317a60 100644
--- a/libgnucash/engine/gnc-budget.h
+++ b/libgnucash/engine/gnc-budget.h
@@ -64,11 +64,6 @@
 #ifndef __GNC_BUDGET_H__
 #define __GNC_BUDGET_H__
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 #include <glib.h>
 
 /** The budget data.*/
@@ -79,6 +74,11 @@ typedef struct _GncBudgetClass GncBudgetClass;
 #include "Account.h"
 #include "Recurrence.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /* --- type macros --- */
 #define GNC_TYPE_BUDGET            (gnc_budget_get_type ())
 #define GNC_BUDGET(o)              \
diff --git a/libgnucash/engine/gnc-date-p.h b/libgnucash/engine/gnc-date-p.h
index 94f3639ad1..f8498cd8e9 100644
--- a/libgnucash/engine/gnc-date-p.h
+++ b/libgnucash/engine/gnc-date-p.h
@@ -23,14 +23,15 @@
 
 #ifndef __GNC_DATE_P_H__
 #define __GNC_DATE_P_H__
+
+#include <stdint.h>
+#include "gnc-date.h"
+
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-#include <stdint.h>
-#include "gnc-date.h"
-
 /** Convert a given date/time format from UTF-8 to an encoding suitable for the
  *  strftime system call.
  *
diff --git a/libgnucash/engine/gncBusiness.h b/libgnucash/engine/gncBusiness.h
index 2fe054d1d4..ecdd785fb4 100644
--- a/libgnucash/engine/gncBusiness.h
+++ b/libgnucash/engine/gncBusiness.h
@@ -39,6 +39,11 @@
 #include "qof.h"
 #include "Account.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /* KVP key for report PDF directories */
 #define OWNER_EXPORT_PDF_DIRNAME "export-pdf-directory"
 #define LAST_POSTED_TO_ACCT "last-posted-to-acct"
@@ -93,5 +98,8 @@ OwnerList * gncBusinessGetOwnerList (QofBook *book, QofIdTypeConst type_name,
  * liabilities and equity accounts. */
 gboolean gncBusinessIsPaymentAcctType (GNCAccountType type);
 
+#ifdef __cplusplus
+}
+#endif
 
 #endif /* GNC_BUSINESS_H_ */
diff --git a/libgnucash/engine/gncCustomer.h b/libgnucash/engine/gncCustomer.h
index adf6eb7805..fa7c6e1ae6 100644
--- a/libgnucash/engine/gncCustomer.h
+++ b/libgnucash/engine/gncCustomer.h
@@ -31,10 +31,6 @@
 #ifndef GNC_CUSTOMER_H_
 #define GNC_CUSTOMER_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /** @struct GncCustomer
 
 credit, discount and shipaddr are unique to GncCustomer\n
@@ -66,6 +62,10 @@ typedef struct _gncCustomerClass GncCustomerClass;
 #include "gncTaxTable.h"
 #include "gncJob.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define GNC_ID_CUSTOMER       "gncCustomer"
 
 /* --- type macros --- */
diff --git a/libgnucash/engine/gncEmployee.h b/libgnucash/engine/gncEmployee.h
index b9399b2008..17060592bb 100644
--- a/libgnucash/engine/gncEmployee.h
+++ b/libgnucash/engine/gncEmployee.h
@@ -31,16 +31,16 @@
 #ifndef GNC_EMPLOYEE_H_
 #define GNC_EMPLOYEE_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct _gncEmployee GncEmployee;
 typedef struct _gncEmployeeClass GncEmployeeClass;
 
 #include "gncAddress.h"
 #include "Account.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define GNC_ID_EMPLOYEE "gncEmployee"
 
 /* --- type macros --- */
diff --git a/libgnucash/engine/gncInvoice.h b/libgnucash/engine/gncInvoice.h
index b78f3dfd2c..3a5f71d6e8 100644
--- a/libgnucash/engine/gncInvoice.h
+++ b/libgnucash/engine/gncInvoice.h
@@ -36,10 +36,6 @@ transaction and lot for the posted invoice.
 #ifndef GNC_INVOICE_H_
 #define GNC_INVOICE_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 struct _gncInvoice;
 typedef struct _gncInvoice GncInvoice;
 typedef struct _gncInvoiceClass GncInvoiceClass;
@@ -54,6 +50,10 @@ typedef GList GncInvoiceList;
 #include "qofbook.h"
 #include "gnc-pricedb.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define GNC_ID_INVOICE    "gncInvoice"
 
 typedef enum
diff --git a/libgnucash/engine/gncVendor.h b/libgnucash/engine/gncVendor.h
index 314ebe1648..c7d2f63ccb 100644
--- a/libgnucash/engine/gncVendor.h
+++ b/libgnucash/engine/gncVendor.h
@@ -31,10 +31,6 @@
 #ifndef GNC_VENDOR_H_
 #define GNC_VENDOR_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct _gncVendor GncVendor;
 typedef struct _gncVendorClass GncVendorClass;
 
@@ -43,6 +39,10 @@ typedef struct _gncVendorClass GncVendorClass;
 #include "gncTaxTable.h"
 #include "gncJob.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define GNC_ID_VENDOR       "gncVendor"
 
 /* --- type macros --- */
diff --git a/libgnucash/engine/guid.h b/libgnucash/engine/guid.h
index f43f194d16..850fe9a56b 100644
--- a/libgnucash/engine/guid.h
+++ b/libgnucash/engine/guid.h
@@ -26,13 +26,13 @@
 #define GUID_H
 
 #include <glib-object.h>
+#include <stddef.h>
+
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-#include <stddef.h>
-
 /** @addtogroup Entity
     @{ */
 /** @addtogroup GncGUID
diff --git a/libgnucash/engine/mocks/fake-qofquery.h b/libgnucash/engine/mocks/fake-qofquery.h
index 803f56dbd6..69f418e1e6 100644
--- a/libgnucash/engine/mocks/fake-qofquery.h
+++ b/libgnucash/engine/mocks/fake-qofquery.h
@@ -11,10 +11,7 @@
 
 #include <qofquery.h>
 
-extern "C"
-{
 #include <Query.h>
-}
 
 /** Fake object providing functionality similar to QofQuery
  *
diff --git a/libgnucash/engine/mocks/gmock-Split.h b/libgnucash/engine/mocks/gmock-Split.h
index 62cbf52ed6..ce022fb2d0 100644
--- a/libgnucash/engine/mocks/gmock-Split.h
+++ b/libgnucash/engine/mocks/gmock-Split.h
@@ -4,10 +4,7 @@
 #include <gmock/gmock.h>
 
 #include <Split.h>
-extern "C"
-{
 #include <SplitP.h>
-}
 
 #include "gmock-qofbook.h"
 #include "gmock-gobject.h"
diff --git a/libgnucash/engine/mocks/gmock-Transaction.h b/libgnucash/engine/mocks/gmock-Transaction.h
index e866c7d8fb..b0537ed50f 100644
--- a/libgnucash/engine/mocks/gmock-Transaction.h
+++ b/libgnucash/engine/mocks/gmock-Transaction.h
@@ -4,10 +4,7 @@
 #include <gmock/gmock.h>
 
 #include <Transaction.h>
-extern "C"
-{
 #include <TransactionP.h>
-}
 
 #include "gmock-gobject.h"
 
diff --git a/libgnucash/engine/qof-win32.cpp b/libgnucash/engine/qof-win32.cpp
index 2c83e25c31..ecae138c6f 100644
--- a/libgnucash/engine/qof-win32.cpp
+++ b/libgnucash/engine/qof-win32.cpp
@@ -21,13 +21,8 @@
  * Boston, MA  02110-1301,  USA       gnu@gnu.org
  */
 
-#ifdef __cplusplus
 #include <glib.h>
 
-extern "C"
-{
-#endif
-
 #include <config.h>
 
 #include "gnc-date-p.h"
@@ -35,10 +30,6 @@ extern "C"
 #include <windows.h>
 #include <stdlib.h>
 
-#ifdef __cplusplus
-}
-#endif
-
 static GHashTable *picture_to_format = NULL;
 G_LOCK_DEFINE_STATIC(picture_to_format);
 
diff --git a/libgnucash/engine/qofbook.h b/libgnucash/engine/qofbook.h
index dc52cf4aad..0b2d663639 100644
--- a/libgnucash/engine/qofbook.h
+++ b/libgnucash/engine/qofbook.h
@@ -46,11 +46,6 @@ class GncOptionDB;
 #else
 typedef struct GncOptionDB GncOptionDB;
 #endif
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 /* We only want a few things exported to Guile */
 #ifndef SWIG
 
@@ -64,6 +59,11 @@ typedef struct KvpValueImpl KvpValue;
 #include "qofinstance.h"
 #include "qofbackend.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /* --- type macros --- */
 #define QOF_TYPE_BOOK            (qof_book_get_type ())
 #define QOF_BOOK(o)              \
@@ -440,11 +440,11 @@ void qof_book_options_delete (QofBook *book, GSList *path);
 /** deprecated */
 #define qof_book_get_guid(X) qof_entity_get_guid (QOF_INSTANCE(X))
 
-#endif /* SWIG */
 #ifdef __cplusplus
 }
 #endif
 
+#endif /* SWIG */
 #endif /* QOF_BOOK_H */
 /** @} */
 /** @} */
diff --git a/libgnucash/engine/qofid.h b/libgnucash/engine/qofid.h
index ff8de1b448..a7c9bc0bcf 100644
--- a/libgnucash/engine/qofid.h
+++ b/libgnucash/engine/qofid.h
@@ -76,11 +76,6 @@
 #include <string.h>
 #include "guid.h"
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 /** QofIdType declaration */
 typedef const gchar * QofIdType;
 /** QofIdTypeConst declaration */
@@ -90,6 +85,11 @@ typedef struct QofCollection_s QofCollection;
 
 #include "qofinstance.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 #define QOF_ID_NONE           NULL
 #define QOF_ID_NULL           "null"
 
diff --git a/libgnucash/engine/qoflog.h b/libgnucash/engine/qoflog.h
index 2597e9d8fe..348891c5fe 100644
--- a/libgnucash/engine/qoflog.h
+++ b/libgnucash/engine/qoflog.h
@@ -85,16 +85,16 @@
 #ifndef _QOF_LOG_H
 #define _QOF_LOG_H
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 #include <stdarg.h>
 #include <stdio.h>
 #include <glib.h>
 #include "qofutil.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 typedef const gchar* QofLogModule;
 
 #define QOF_MOD_ENGINE "qof.engine"
diff --git a/libgnucash/engine/qofutil.h b/libgnucash/engine/qofutil.h
index 0ce7cb168c..ddbd39d2f0 100644
--- a/libgnucash/engine/qofutil.h
+++ b/libgnucash/engine/qofutil.h
@@ -32,11 +32,6 @@
 #ifndef QOF_UTIL_H
 #define QOF_UTIL_H
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 #include <stddef.h>
 #include "qof.h"
 #include "qoflog.h"
@@ -45,6 +40,11 @@ extern "C"
 #include "qofbook.h"
 #include "qofinstance.h"
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
 /** Do not use these for printf, only scanf */
 #if HAVE_SCANF_LLD
 # define QOF_SCANF_LLD "%lld"
diff --git a/libgnucash/engine/test-core/test-engine-stuff.h b/libgnucash/engine/test-core/test-engine-stuff.h
index b988250455..9c70ec419b 100644
--- a/libgnucash/engine/test-core/test-engine-stuff.h
+++ b/libgnucash/engine/test-core/test-engine-stuff.h
@@ -24,11 +24,8 @@
 
 #ifndef TEST_ENGINE_STUFF_H
 #define TEST_ENGINE_STUFF_H
+
 #include <glib.h>
-#ifdef __cplusplus
-extern "C"
-{
-#endif
 #include <stdlib.h>
 #include <stdint.h>
 
@@ -46,6 +43,10 @@ typedef struct KvpFrameImpl KvpFrame;
 #define __KVP_FRAME
 #endif
 
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 time64 get_random_time(void);
 
 KvpValue* get_random_kvp_value(int type);
diff --git a/libgnucash/engine/test/test-gnc-guid-old.cpp b/libgnucash/engine/test/test-gnc-guid-old.cpp
index a64adb3361..422a0ae900 100644
--- a/libgnucash/engine/test/test-gnc-guid-old.cpp
+++ b/libgnucash/engine/test/test-gnc-guid-old.cpp
@@ -24,13 +24,11 @@
 #include <glib.h>
 #include "../guid.hpp"
 
-extern "C"
-{
 #include <config.h>
 #include <string.h>
 #include <unittest-support.h>
-void test_suite_gnc_guid (void);
-}
+
+extern "C" void test_suite_gnc_guid (void);
 
 /*Can be included as c++, because it's c++ tolerant*/
 #include "../guid.h"
diff --git a/libgnucash/engine/test/test-qofsession-old.cpp b/libgnucash/engine/test/test-qofsession-old.cpp
index 4c73365eab..827392541f 100644
--- a/libgnucash/engine/test/test-qofsession-old.cpp
+++ b/libgnucash/engine/test/test-qofsession-old.cpp
@@ -23,11 +23,8 @@
 #include "../guid.hpp"
 #include <glib.h>
 
-extern "C"
-{
 #include <config.h>
 #include <unittest-support.h>
-}
 
 #include "../qof.h"
 #include "../qofbackend-p.h"