[glibmm] g[io|lib]mmconfig.h.*: Don't dllimport on MinGW

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

commit 6e242eaba57bbc0f44ab7c4959d2e66ceeeededa
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Mar 8 12:01:43 2021 +0800

    g[io|lib]mmconfig.h.*: Don't dllimport on MinGW
    
    This will fix warnings when building items using glibmm and giomm with
    MinGW/GCC.
    
    Please see: https://gitlab.gnome.org/GNOME/gtkmm/-/issues/90

 gio/giommconfig.h.in      | 4 +++-
 gio/giommconfig.h.meson   | 4 +++-
 glib/glibmmconfig.h.in    | 4 +++-
 glib/glibmmconfig.h.meson | 4 +++-
 4 files changed, 12 insertions(+), 4 deletions(-)
---
diff --git a/gio/giommconfig.h.in b/gio/giommconfig.h.in
index b9579c6e..714ad879 100644
--- a/gio/giommconfig.h.in
+++ b/gio/giommconfig.h.in
@@ -26,8 +26,10 @@
 #ifdef GIOMM_DLL
 # if defined(GIOMM_BUILD)
 #  define GIOMM_API __declspec(dllexport)
-# else
+# elif !defined (__GNUC__)
 #  define GIOMM_API __declspec(dllimport)
+# else /* don't dllimport classes/methods on GCC/MinGW */
+#  define GIOMM_API
 # endif
 /* Build a static library or non-native-Windows library */
 #else
diff --git a/gio/giommconfig.h.meson b/gio/giommconfig.h.meson
index 9ac31c6d..41232323 100644
--- a/gio/giommconfig.h.meson
+++ b/gio/giommconfig.h.meson
@@ -26,8 +26,10 @@
 #ifdef GIOMM_DLL
 # if defined(GIOMM_BUILD)
 #  define GIOMM_API __declspec(dllexport)
-# else
+# elif !defined (__GNUC__)
 #  define GIOMM_API __declspec(dllimport)
+# else /* don't dllimport classes/methods on GCC/MinGW */
+#  define GIOMM_API
 # endif
 /* Build a static library or non-native-Windows library */
 #else
diff --git a/glib/glibmmconfig.h.in b/glib/glibmmconfig.h.in
index b1c2d8db..6fd1c874 100644
--- a/glib/glibmmconfig.h.in
+++ b/glib/glibmmconfig.h.in
@@ -97,8 +97,10 @@
 #ifdef GLIBMM_DLL
 # if defined(GLIBMM_BUILD)
 #  define GLIBMM_API __declspec(dllexport)
-# else
+# elif !defined (__GNUC__)
 #  define GLIBMM_API __declspec(dllimport)
+# else /* don't dllimport classes/methods on GCC/MinGW */
+#  define GLIBMM_API
 # endif
 /* Build a static or non-native-Windows library */
 #else
diff --git a/glib/glibmmconfig.h.meson b/glib/glibmmconfig.h.meson
index 16b96833..ef4753d7 100644
--- a/glib/glibmmconfig.h.meson
+++ b/glib/glibmmconfig.h.meson
@@ -99,8 +99,10 @@
 #ifdef GLIBMM_DLL
 # if defined(GLIBMM_BUILD)
 #  define GLIBMM_API __declspec(dllexport)
-# else
+# elif !defined (__GNUC__)
 #  define GLIBMM_API __declspec(dllimport)
+# else /* don't dllimport classes/methods on GCC/MinGW */
+#  define GLIBMM_API
 # endif
 /* Build a static or non-native-Windows library */
 #else