Design a code module

This article demonstrates how to design a new code module.

Header File

A header file:

Shall have #pragma once attribute (google it for the reason)

Shall NEVER have variables defined

//- Note: Remove all lines from your code that start with //-

//- Put this line as the very first line in your header module

#pragma once

//- #include all header files that THIS header needs

//- Do not include headers here that are not needed

//- For example, we do not need gpio.h file here, but maybe you can move this to switch_led.c

#include "gpio.h"

 

//- DO NOT put any variables here, like so:

static int do_not_do_this;

int definitely_do_not_do_this;

//- All functions without paramters should be marked as (void)

void switch_led_logic__initialize(void);

void switch_led_logic__run_once(void);

#pragma once is a replacement of

#ifndef YOUR_FILE_NAME__

#define YOUR_FILE_NAME__

 

void your_api(void);

#endif

Intent of #pragma once and #ifndef

When other code modules #include your header file, you only want functions to be declared once

The name of #ifndef can be anything unique, but must not conflict with other files

#include literally copies and pastes the contents of the file in the file wherever you have the #include

Source File

A source file:

Shall have all variables defined as static; this will keep their visibility private to their file

//- Note: Remove all lines from your code that start with //-

//- Include the header file for which this code modules belongs to

#include "switch_led_logic.h"

//- Declare all variables as STATIC

static gpio_s my_led;

//- Define your public functions (part of this module's header file)

void switch_led_logic__initialize(void) {

 my_led = gpio__construct_as_output(GPIO__PORT_2, 0);

}

void switch_led_logic__run_once(void) {

 gpio__set(my_led);

}

Unit Test file

A unit-test file:

Shall #include the headers that you want (those that should not be "mocked")

Shall #include Mock headers to generate stubs (rather than the full implementation)

Useful stuff

Clang auto-formatter will format the source code for you. It will also sort the #includes, so it is recommended to put an empty line such that it sorts the #includes more elegantly. For example, you can separate the FreeRTOS includes, system includes, and other includes.

//- Note: Remove all lines from your code that start with //-

//- Include system includes first

#include <stdio.h>

//- FreeRTOS requires this header file inclusion before any of its soure code

//- This only applies to code included from FreeRTOS

#include "FreeRTOS.h"

#include "semphr.h"

#include "task.h"

//- Clang will sort these

#include "abc.h"

#include "def.h"

Try the following

Have two code modules, such as main.c and periodic_callbacks.c include a header file that does not have #pragma once and observe what happens when you compile