C Coding Standard

1 共同

Rule 1 编译的Warnings不能被忽略掉

Rule 2 在已有Code或者三方的code基础上的改动，同意使用原来的coding standard

Rule 3 假设同意C和C++都訪问的同样的C的header 文件, extern C 必须在header文件中

#ifdef __cplusplus
extern "C" {
#endif

/* body of header */

#ifdef __cplusplus
}
#endif

2 命名规则

Rule4 全部名字的定义在16个字节范围内，最多不要超过31个

Rule5 名字的定义仅仅有字母数字和下划线

Rule6 不要使用保留名字

Rule7 代码文件以.h, .c 结尾

Rule8 代码的文件格式必须保持UNIX file format

Rule9 文件名称小写，当超过一个单词描写叙述时。用下划线分隔

structured_data_display.h	
structured_data_display.c

Rule10 Typedefs, and enumerated types, structure types and union types 小写并用下划线分隔多个单词描写叙述, 结尾应以type结尾

typedef UINT8 user_data_struct_type

Rule11 宏定义, Enum的值，必须大写并下面划线分隔多个单词

 #define USER_DATA_MAX_ERROR_CODES    15
enum user_data_struct_type
{
    USER_DATA_ERROR_INVALID_DATA,
    USER_DATA_ERROR_FAILURE
 };

Rule12 函数名必须是动词而且小写和下划线分隔多个单词

handle_error 
check_for_error               /* NOT errorCheck */

Rule13 全局变量必须以g开头并下面划线分隔单词

g_default_interface

Rule14 函数的參数小写单词

void start_engine(engine_type*        myengine, 
                        UINT8          engine_id,
                        const UINT32*  protected_data);

Rule15 structure的成员变量有下面规则

名字	标记	演示样例
static	s_	static UINT8 s_some_number
static	s_	static UINT8 s_some_number
constant	c_	const UINT8 c_some_number
	cp_	const user_data_type* cp_user_data

3 Files

Rule16 每一个include的必须有机制防止多重包括

#ifndef FOO_H
#define FOO_H
        
/* The rest of the file*/
  	      
#endif

Rule17 相对路径的linux文件不同意出如今#include里

// NOT ALLOWED
#include <../foo/include/foo.h>

Rule18 头文件不同意有实现的代码

Rule19 每一个头文件仅仅include 其它有依赖的，包括相关定义的头文件，不include 全局性的头文件

Rule20 代码文件（.c)须要include 全局头文件以及相关头文件

4 代码风格和间隔

Rule21 在不论什么修改的文件都须要加上公司confidential的标识

/* -------------------------------------------------------------------------------
     Copyright (C) 2011, Nollec Wireless  CO. LTD. All Rights Reserved

     Revision History:
       Bug/Feature ID         Author                   Modification Date                      Description 
     ------------------       -------------------         ------------------            ---------------------
      BugID/FeatureID      developer name       YYYY/MM/DD                          brief discription

----------------------------------------------------------------------------------*/

Rule22 在不论什么修改或者新建的文件都须要加上公司confidential的标识

Rule23 Revision History 在Feature开发完毕或Bug解决完毕后必须更新

Rule24 全部的Comments必须用英文填写, 而且不能嵌入

Rule25 代码缩进的时候不要用Tab，用4个空格取代

（跟编辑器有关,可设置）
void func()
｛
      if (something bad)
      {
          ...
          if (another thing bad)
         {

         }
 }

Rule26 Switch 必须有default

switch (testValue)
{
    case VALUE_1:
        /* Body for case 1. */
        break;
    case VALUE_2:
        /* Body for case 2. */
        break;
    default:
        /* Body for default. */
        break;
}

Rule27 不要在 . 或-> 前后有空格

Rule28 变量的声明应尽量控制到小的范围内

Rule29 指针 * 应该紧跟类型之后。 地址 &应该在变量名之前

Rule30 变量常量定义一定要有意义。不要用magic number

x = 100*10+1; //NOT ALLOWEDnumber = 100*10+1;

Rule31 每一个变量定义都要分行写。并且一定要给初值

UINT8 i, j;              /* NOT RECOMMENDED */
UINT8 i = INIT_VALUE;    /* GOOD */
UINT8 j = INIT_VALUE;    /* GOOD */

Rule31 全部状态变量或者enum的变量要明白赋予其值

/* INCORRECT*/
if (cpCurrentState == CP_L3_STATE_TYPE_D1)
{
    cpCurrentState++;
} 
/*CORRECT*/
if (cp_currentState == CP_L3_STATE_TYPE_D1)
{
    cp_currentState = CP_L3_STATE_TYPE_D2;
}

Rule32 全部global的声明都要在一个header文件中

Rule33 常量声明须要有明白含义

(Does not meet requirements)
#define ONE			1
#define TWO			2

 (Meets requirements)
#define NUM_LOOPS_FOR_AD_READ	4
#define NUM_SAMPLES_TAKEN		8

Rule34 一个constant不能付给另外一个constant

Rule35 NULL仅仅用于指针的初始化和比較

Rule36 常量用在编译开关时候，一定要在编译控制的区域内

#define DEBUG 4  
 /* if undefined, disables debugging */
/* set to 1 - 4 for desired debugging level */
/* This usage of DEBUG in the for loop control statement is  
 * allowed since the statement is fully enclosed within the
 * conditionally compiled section of code.
 */
#ifdef DEBUG 
for (i = 0; i < DEBUG; i++)  
{
    printf("i = %d
", i);
}
#endif

Example 31 -	Example (Incorrect Usage)
#define DEBUG 4
#ifdef DEBUG       /* usage here is fine */ 
    /* do something special */
#endif
/* the code statement below is outside the segment controlled by 
 * the #ifdef and therefore should NOT use DEBUG.
 */
for (i = 0; ((i < 5) && DEBUG); i++) 
{
    printf("i = %d
", i);
}

Rule37 #ifdef #endif 用于编译时要有足够的凝视。并且#endif要有 //凝视相应的#ifdef

Rule38 用typedef 而不是#define来定义类型

Rule39 The following types shall be defined in a global header file and shall be used in place of the C language int types:

•	INT8: This type stores 8-bit signed numeric values.
•	UINT8: This type stores 8-bit unsigned numeric values.
•	INT16: This type stores 16-bit signed numeric values.
•	UINT16: This type stores 16-bit unsigned numeric values.
•	INT32: This type stores 32-bit signed numeric values.
•	UINT32: This type stores 32-bit unsigned numeric values.
•	BOOLEAN: Ideally, this type is an enumerated type that names the boolean values TRUE (1) and FALSE (0). However, some compilers may not store this efficiently. An alternative is typedef UINT8 BOOLEAN;
That simply defines BOOLEAN as an 8-bit unsigned value which is distinct from UINT8. In this case, the constants TRUE and FALSE will have to be defined constants.

Rule31 一个函数应该仅仅有一个return出口

Rule32 不要使用没有明白定义的參数

Rule33 函数return指针假设failure。则须要return NULL

Rule34 函数參数是单列数组不须要明白大小

 (Correct Usage)
void functionName
(
    UINT8 x[],  /* array with "size" elements */
    UINT8 size  /* number of elements in x */
);
(Incorrect Usage)
void functionName (UINT8 x[10]);

Rule35 不论什么宏定义的拓展须要加上括号来限定

 (Correct):
#define A_CONSTANT	(ANOTHER_CONSTANT + 1)
a = ACONSTANT * 2;
(Incorrect):
#define A_CONSTANT	ANOTHER_CONSTANT + 1
a = ACONSTANT * 2;

Flow control, expressions

Rule36 Switch case必需要有break结束

Rule37 Switch default必需要有来控制以外情况

Rule38 不要使用Goto

Rule39 在比較的时候 左边要放常量

// NOT RECOMMENDED, imagine you forget one of the “=” signs
If (PHONE == IS_RESET)
{
}
// GOOD, the following statement eliminates the possible errors explained above 
// and easier to follow the value that you are looking for
If (IS_RESET == PHONE)
{
}

Rule40 在使用else if的时候，else的部分须要加上

Rule41 if/else/while/for/do的区块不管一行还是多行，一定要加｛｝

// NOT RECOMMENDED
if (something)
   if (something else)
       doThis();
   else
       while (input)
           doThat();

// GOOD
if (something)
{
   if (something else)
   {
       doThis();
   }
   else
   {
       while (input)
       {
           doThat();
       }
   }
}

Memory

Rule42 一定保证从调用函数分配的内存在使用完成后释放内存, 一定在此调用函数凝视提醒

Dangerous memory management   
error_code_type* myfunction(void)
{
    error_code_type* p_temp = malloc (sizeof(error_code_type));
    return p_temp;
    /* p_temp is never de-allocated and the user of myFunc cannot de-allocate*/
    /* because a temporary copy of that instance is returned.*/
    /* Calling user code shall take of the memory deallocating which will create*/
    /* complexity and confusion*/
}

Rule43 在deference引用指针之前一定要对指针判定是否为NULL

UINT32* p_number = NULL;if (NULL == p_number){}

其它

Rule44 编译器相关的扩展在有必要的时候使用

#ifdef _HC11_
#define DIRECT _direct_ram
#else /* not _HC11_ */
#define DIRECT
#endif

/* nSize located in direct RAM in embedded, normal RAM in UNIX */
DIRECT UINT8 nSize;

Rule45 编译器相关的扩展在有必要的时候使用

Rule46 全部丢失性的类型转换要明白cast

INT8   signed_value;
UINT16 long_value;
UINT8  short_value;

/* Loss here is in accuracy going from signed to unsigned */
signed_value= (UINT8) short_value;
/* Loss here is in size, going from a 16 bit value to an 8 bit */
signed_value= (INT8) long_value;

Rule47 数组的訪问仅仅能用方括号的形式訪问，不要使用deference * 来訪问

/*INCORRECT*/
*(masterList + 10) = 0;

/*CORRECT*/
masterList[10] = 0;

Rule48 在condition如果确定要利用肯定的逻辑