tests/external_module_dirs: add auto-init function

tests/external_module_dirs/README.md

@@ -8,5 +8,4 @@ It demonstrates:
  * Adding a module with source code
  * Setting a header include directory
  * Adding dependencies, which are evaluated before other modules dependencies
-
-If the application compiles, everything is ok.
+ * Registering a module for auto-initialization

tests/external_module_dirs/external_modules/external_module/external_module.c

@@ -20,5 +20,16 @@
  */
 
 #include "external_module.h"
+#include "auto_init_utils.h"
 
+#define PRIO 1111
+
+AUTO_INIT(auto_init_external_module, PRIO);
+
+bool external_module_initialized = false;
 char *external_module_message = "Linking worked";
+
+void auto_init_external_module(void)
+{
+    external_module_initialized = true;
+}

tests/external_module_dirs/external_modules/external_module/include/external_module.h

@@ -20,15 +20,28 @@
 #ifndef EXTERNAL_MODULE_H
 #define EXTERNAL_MODULE_H
 
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/**
+ * @brief   true: this module hase been initialized
+ *          false: this module has not been initialized
+ */
+extern bool external_module_initialized;
+
 /**
  * @brief   A simple string message
  */
 extern char *external_module_message;
 
+/**
+ * @brief   Auto-init function of this module to be called on system start up
+ */
+void auto_init_external_module(void);
+
 #ifdef __cplusplus
 }
 #endif

tests/external_module_dirs/main.c

@@ -32,7 +32,11 @@
 
 int main(void)
 {
-    puts("If it compiles, it works!");
     printf("Message: %s\n", external_module_message);
+    if (!external_module_initialized) {
+        puts("External module has not been initialized.");
+        return 1;
+    }
+    puts("Initialization worked!");
     return 0;
 }