freertos.h 内容解读

参考：

freestanding implemantion需要提供 和

AMD1 标准后，再增加一个

C99 标准后，增加 和

C11 标准后，增加 和

/*

 * Check all the required application specific macros have been defined.

 * These macros are application specific and (as downloaded) are defined

 * within FreeRTOSConfig.h.

 */

#ifndef configMINIMAL_STACK_SIZE

    #error Missing definition:  configMINIMAL_STACK_SIZE must be defined in FreeRTOSConfig.h.  configMINIMAL_STACK_SIZE defines the size (in words) of the stack allocated to the idle task.  Refer to the demo project provided for your port for a suitable value.

#endif

#ifndef configMAX_TASK_NAME_LEN

    #define configMAX_TASK_NAME_LEN 16

#endif

#ifndef configIDLE_SHOULD_YIELD

    #define configIDLE_SHOULD_YIELD    1

#endif

/*

 * In line with software engineering best practice, FreeRTOS implements a strict

 * data hiding policy, so the real structures used by FreeRTOS to maintain the

 * state of tasks, queues, semaphores, etc. are not accessible to the application

 * code.  However, if the application writer wants to statically allocate such

 * an object then the size of the object needs to be know.  Dummy structures

 * that are guaranteed to have the same size and alignment requirements of the

 * real objects are used for this purpose.  The dummy list and list item

 * structures below are used for inclusion in such a dummy structure.

 */

根据最佳实践、rtos 源码实现了数据隐藏。 rtos 用于维护 task  queues semaphores 状态的数据结构对于应用开发（使用rtos）是不可访问的。但是，有时使用rtos 时，需要静态分配一个用户维护系统状态对象，就需要用到对应的数据结构定义。下面就是一些保持了对齐和大小的假的 数据结构定义，rtos 使用者可以使用这些假的结构体定义来定义对象。

struct xSTATIC_LIST_ITEM

    TickType_t xDummy1;

    void *pvDummy2[ 4 ];

};

typedef struct xSTATIC_LIST_ITEM StaticListItem_t;