[gtk/master.msvc: 26/27] modules: Fix build on Visual Studio

[Chun-wei Fan <fanchunwei src gnome org>]

commit acd9c12667a021936b30e0fa8f43d3a8c7133cf7
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Thu Jun 4 16:27:56 2020 +0800

    modules: Fix build on Visual Studio
    
    Visual Studio does not allow decorating functions with '__declspec (dllexport)'
    if a prototype exists and is not decorated with '__declspec (dllexport)' as
    well, so we cannot just decorate g_io_module_[load|unload|query] in the various
    module sources with G_MODULE_EXPORT because the prototypes of these functions
    have been marked with _GLIB_EXTERN, which equates to 'extern' unless overridden
    
    Fix this by overriding _GLIB_EXTERN with the appropriate visibility flag, as we
    have used to define _GDK_EXTERN.  Unfortunately, we can't just use _GDK_EXTERN
    G_MODULE_EXPORT as they may have not been defined yet for our use
    
    Do this across the board for all modules, even if they are not buildable on
    Visual Studio nor Windows, for consistency's sake.

 meson.build                                       | 16 ++++++++++------
 modules/media/gtkgstmediafile.c                   |  3 ---
 modules/media/meson.build                         |  6 +++++-
 modules/printbackends/gtkprintbackendcloudprint.c |  3 ---
 modules/printbackends/gtkprintbackendcups.c       |  3 ---
 modules/printbackends/gtkprintbackendfile.c       |  3 ---
 modules/printbackends/gtkprintbackendlpr.c        |  3 ---
 modules/printbackends/meson.build                 |  1 +
 8 files changed, 16 insertions(+), 22 deletions(-)
---
diff --git a/meson.build b/meson.build
index 9295163603..946027a278 100644
--- a/meson.build
+++ b/meson.build
@@ -286,15 +286,19 @@ endif
 common_cflags = cc.get_supported_arguments(test_cflags)
 
 # Symbol visibility
+
+if os_win32
+  visibility_define = '__declspec(dllexport) extern'
+else
+  visibility_define = '__attribute__((visibility("default"))) extern'
+endif
+
 if get_option('default_library') != 'static'
+  cdata.set('_GDK_EXTERN', visibility_define)
   if os_win32
     cdata.set('DLL_EXPORT', true)
-    cdata.set('_GDK_EXTERN', '__declspec(dllexport) extern')
-    if cc.get_id() != 'msvc'
-      common_cflags += ['-fvisibility=hidden']
-    endif
-  else
-    cdata.set('_GDK_EXTERN', '__attribute__((visibility("default"))) extern')
+  endif
+  if cc.get_id() != 'msvc'
     common_cflags += ['-fvisibility=hidden']
   endif
 endif
diff --git a/modules/media/gtkgstmediafile.c b/modules/media/gtkgstmediafile.c
index 5988ef38c3..b094796fd5 100644
--- a/modules/media/gtkgstmediafile.c
+++ b/modules/media/gtkgstmediafile.c
@@ -97,7 +97,6 @@ G_DEFINE_TYPE_EXTENDED (GtkGstMediaFile, gtk_gst_media_file, GTK_TYPE_MEDIA_FILE
                         G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE,
                                                gtk_gst_media_file_paintable_init))
 
-G_MODULE_EXPORT
 void
 g_io_module_load (GIOModule *module)
 {
@@ -109,7 +108,6 @@ g_io_module_load (GIOModule *module)
                                   10);
 }
 
-G_MODULE_EXPORT
 G_GNUC_NORETURN
 void
 g_io_module_unload (GIOModule *module)
@@ -117,7 +115,6 @@ g_io_module_unload (GIOModule *module)
   g_assert_not_reached ();
 }
 
-G_MODULE_EXPORT
 char **
 g_io_module_query (void)
 {
diff --git a/modules/media/meson.build b/modules/media/meson.build
index c6dbed1f26..59124d3154 100644
--- a/modules/media/meson.build
+++ b/modules/media/meson.build
@@ -23,7 +23,11 @@ endif
 media_subdir = 'gtk-4.0/@0@/media'.format(gtk_binary_version)
 media_install_dir = join_paths(get_option('libdir'), media_subdir)
 
-extra_c_args = ['-DGTK_COMPILATION']
+extra_c_args = [
+  '-DGTK_COMPILATION',
+  '-D_GLIB_EXTERN=@0@'.format(visibility_define),
+]
+
 extra_c_args += common_cflags
 
 if media_backends.contains('ffmpeg')
diff --git a/modules/printbackends/gtkprintbackendcloudprint.c 
b/modules/printbackends/gtkprintbackendcloudprint.c
index 99dc5f3665..6a5d7755af 100644
--- a/modules/printbackends/gtkprintbackendcloudprint.c
+++ b/modules/printbackends/gtkprintbackendcloudprint.c
@@ -103,7 +103,6 @@ void                 t_goa_account_free                 (gpointer data);
 
 G_DEFINE_DYNAMIC_TYPE (GtkPrintBackendCloudprint, gtk_print_backend_cloudprint, GTK_TYPE_PRINT_BACKEND)
 
-G_MODULE_EXPORT
 void
 g_io_module_load (GIOModule *module)
 {
@@ -119,13 +118,11 @@ g_io_module_load (GIOModule *module)
                                   10);
 }
 
-G_MODULE_EXPORT
 void
 g_io_module_unload (GIOModule *module)
 {
 }
 
-G_MODULE_EXPORT
 char **
 g_io_module_query (void)
 {
diff --git a/modules/printbackends/gtkprintbackendcups.c b/modules/printbackends/gtkprintbackendcups.c
index 58dd95bbbe..893ced4c16 100644
--- a/modules/printbackends/gtkprintbackendcups.c
+++ b/modules/printbackends/gtkprintbackendcups.c
@@ -236,7 +236,6 @@ static void                 secrets_service_vanished_cb             (GDBusConnec
 
 G_DEFINE_DYNAMIC_TYPE(GtkPrintBackendCups, gtk_print_backend_cups, GTK_TYPE_PRINT_BACKEND)
 
-G_MODULE_EXPORT
 void
 g_io_module_load (GIOModule *module)
 {
@@ -251,13 +250,11 @@ g_io_module_load (GIOModule *module)
                                   10);
 }
 
-G_MODULE_EXPORT
 void
 g_io_module_unload (GIOModule *module)
 {
 }
 
-G_MODULE_EXPORT
 char **
 g_io_module_query (void)
 {
diff --git a/modules/printbackends/gtkprintbackendfile.c b/modules/printbackends/gtkprintbackendfile.c
index 3486805688..071ebec359 100644
--- a/modules/printbackends/gtkprintbackendfile.c
+++ b/modules/printbackends/gtkprintbackendfile.c
@@ -102,7 +102,6 @@ static GtkPageSetup *       file_printer_get_default_page_size     (GtkPrinter
 
 G_DEFINE_DYNAMIC_TYPE(GtkPrintBackendFile, gtk_print_backend_file, GTK_TYPE_PRINT_BACKEND)
 
-G_MODULE_EXPORT
 void
 g_io_module_load (GIOModule *module)
 {
@@ -116,13 +115,11 @@ g_io_module_load (GIOModule *module)
                                   10);
 }
 
-G_MODULE_EXPORT
 void
 g_io_module_unload (GIOModule *module)
 {
 }
 
-G_MODULE_EXPORT
 char **
 g_io_module_query (void)
 {
diff --git a/modules/printbackends/gtkprintbackendlpr.c b/modules/printbackends/gtkprintbackendlpr.c
index 0626e594fa..cef1501c30 100644
--- a/modules/printbackends/gtkprintbackendlpr.c
+++ b/modules/printbackends/gtkprintbackendlpr.c
@@ -83,7 +83,6 @@ static void                 gtk_print_backend_lpr_print_stream    (GtkPrintBacke
 
 G_DEFINE_DYNAMIC_TYPE (GtkPrintBackendLpr, gtk_print_backend_lpr, GTK_TYPE_PRINT_BACKEND)
 
-G_MODULE_EXPORT
 void
 g_io_module_load (GIOModule *module)
 {
@@ -97,13 +96,11 @@ g_io_module_load (GIOModule *module)
                                   10);
 }
 
-G_MODULE_EXPORT
 void
 g_io_module_unload (GIOModule *module)
 {
 }
 
-G_MODULE_EXPORT
 char **
 g_io_module_query (void)
 {
diff --git a/modules/printbackends/meson.build b/modules/printbackends/meson.build
index 643a8ba888..40a9379b47 100644
--- a/modules/printbackends/meson.build
+++ b/modules/printbackends/meson.build
@@ -68,6 +68,7 @@ printbackends_args = [
   '-DGTK_COMPILATION',
   '-DGTK_DISABLE_DEPRECATION_WARNINGS',
   '-DGTK_PRINT_BACKEND_ENABLE_UNSUPPORTED',
+  '-D_GLIB_EXTERN=@0@'.format(visibility_define),
 ] + common_cflags
 
 if print_backends.contains('cups')