--- a/src/gui.h
+++ b/src/gui.h
@@ -541,3 +541,29 @@ typedef enum
 # define CONVERT_FROM_UTF8(String) (String)
 # define CONVERT_FROM_UTF8_FREE(String) ((String) = (char_u *)NULL)
 #endif /* FEAT_GUI_GTK */
+
+#ifdef FEAT_GUI_GTK
+/*
+ * The second parameter of g_signal_handlers_disconnect_by_func() is supposed
+ * to be a function pointer which was passed to g_signal_connect_*() somewhere
+ * previously, and hence it must be of type GCallback, i.e., void (*)(void).
+ *
+ * Meanwhile, g_signal_handlers_disconnect_by_func() is a macro calling
+ * g_signal_handlers_disconnect_matched(), and the second parameter of the
+ * former is to be passed to the sixth parameter of the latter the type of
+ * which, however, is declared as void * in the function signature.
+ *
+ * While the ISO C Standard does not require that function pointers be
+ * interconvertible to void *, widely-used compilers such as gcc and clang
+ * do such conversion implicitly and automatically on some platforms without
+ * issuing any warning.
+ *
+ * For Solaris Studio, that is not the case.  An explicit type cast is needed
+ * to suppress warnings on that particular conversion.
+ */
+# if defined(__SUNPRO_C) && defined(USE_GTK3)
+#  define FUNC2GENERIC(func) (void *)(func)
+# else
+#  define FUNC2GENERIC(func) G_CALLBACK(func)
+# endif
+#endif /* FEAT_GUI_GTK */