+/* for VM variables */
+XBT_PUBLIC(void) TRACE_vm_variable_declare (const char *variable);
+XBT_PUBLIC(void) TRACE_vm_variable_declare_with_color (const char *variable, const char *color);
+XBT_PUBLIC(void) TRACE_vm_variable_set (const char *vm, const char *variable, double value);
+XBT_PUBLIC(void) TRACE_vm_variable_add (const char *vm, const char *variable, double value);
+XBT_PUBLIC(void) TRACE_vm_variable_sub (const char *vm, const char *variable, double value);
+XBT_PUBLIC(void) TRACE_vm_variable_set_with_time (double time, const char *vm, const char *variable, double value);
+XBT_PUBLIC(void) TRACE_vm_variable_add_with_time (double time, const char *vm, const char *variable, double value);
+XBT_PUBLIC(void) TRACE_vm_variable_sub_with_time (double time, const char *vm, const char *variable, double value);
+XBT_PUBLIC(xbt_dynar_t) TRACE_get_vm_variables (void);
+
+