[grilo/master.msvc: 6/13] grl-definitions.h: Add _GRL_EXTERN

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

commit 1b2e54438d08c8b2df532545e0c4ed10c22174c7
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Apr 22 14:30:45 2020 +0800

    grl-definitions.h: Add _GRL_EXTERN
    
    This macro can be used to export and import symbols where necessary, on
    compilers that do not support autoexporting mechanisms.  The
    __declspec(dllimport) usage is required for variables that need to be accessed
    from the DLL.

 src/grl-definitions.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/src/grl-definitions.h b/src/grl-definitions.h
index 7ca2899..afc51d6 100644
--- a/src/grl-definitions.h
+++ b/src/grl-definitions.h
@@ -42,4 +42,16 @@
    remain to be sent */
 #define GRL_SOURCE_REMAINING_UNKNOWN -1
 
+#ifndef _GRL_EXTERN
+# if defined (G_OS_WIN32) && !defined (GRL_STATIC)
+#  ifdef GRILO_COMPILATION
+#   define _GRL_EXTERN __declspec(dllexport) extern
+#  else
+#   define _GRL_EXTERN __declspec(dllimport) extern
+#  endif
+# else
+#  define _GRL_EXTERN extern
+# endif
+#endif
+
 #endif