api: only allow including `ModemManager.h' directly

include/ModemManager-enums.h

@@ -17,6 +17,10 @@
 #ifndef _MODEMMANAGER_ENUMS_H_
 #define _MODEMMANAGER_ENUMS_H_
 
+#if !defined (__MODEM_MANAGER_H_INSIDE__)
+#error "Only <ModemManager.h> can be included directly."
+#endif
+
 /**
  * SECTION:mm-enums
  * @short_description: Common enumerations and types in the API.

include/ModemManager-errors.h

@@ -17,6 +17,10 @@
 #ifndef _MODEMMANAGER_ERRORS_H_
 #define _MODEMMANAGER_ERRORS_H_
 
+#if !defined (__MODEM_MANAGER_H_INSIDE__)
+#error "Only <ModemManager.h> can be included directly."
+#endif
+
 #include <ModemManager-names.h>
 
 /**

include/ModemManager.h

@@ -25,6 +25,8 @@
 #ifndef _MODEM_MANAGER_H_
 #define _MODEM_MANAGER_H_
 
+#define __MODEM_MANAGER_H_INSIDE__
+
 /* Public header with DBus Interface, Method, Signal and Property names */
 #include <ModemManager-names.h>