分支语句
为每个case语句添加单个缩进
使用额外的单缩进break语句在每个case或default
/* OK, every case has single indent */
/* OK, every break has additional indent */
switch (check()) {
case 0:
do_a();
break;
case 1:
do_b();
break;
default:
break;
}
/* Wrong, case indent missing */
switch (check()) {
case 0:
do_a();
break;
case 1:
do_b();
break;
default:
break;
}
/* Wrong */
switch (check()) {
case 0:
do_a();
break; /* Wrong, break must have indent as it is under case */
case 1:
do_b(); /* Wrong, indent under case is missing */
break;
default:
break;
}
总是包含default语句
/* OK */
switch (var) {
case 0:
do_job();
break;
default: break;
}
/* Wrong, default is missing */
switch (var) {
case 0:
do_job();
break;
}
如果需要局部变量，则使用花括号并在里面放入break语句。将左花括号放在case语句的同一行
switch (a) {
/* OK */
case 0: {
int32_t a, b;
char c;
a = 5;
/* ... */
break;
}
/* Wrong */
case 1:
{
int32_t a;
break;
}
/* Wrong, break shall be inside */
case 2: {
int32_t a;
}
break;
}
宏和预处理指令
总是使用宏而不是文字常量，特别是对于数字
所有的宏必须是全大写的，并带有下划线_字符(可选)，除非它们被明确标记为function，将来可能会被常规函数语法替换
/* OK */
#define MY_MACRO(x) ((x) * (x))
/* Wrong */
#define square(x) ((x) * (x))
总是用圆括号保护输入参数
/* OK */
#define MIN(x, y) ((x) < (y) ? (x) : (y))
/* Wrong */
#define MIN(x, y) x < y ? x : y
总是用括号保护最终的宏计算
/* Wrong */
#define MIN(x, y) (x) < (y) ? (x) : (y)
#define SUM(x, y) (x) + (y)
/* Imagine result of this equation using wrong SUM implementation */
int32_t x = 5 * SUM(3, 4); /* Expected result is 5 * 7 = 35 */
int32_t x = 5 * (3) + (4); /* It is evaluated to this, final result = 19 which is not what we expect */
/* Correct implementation */
#define MIN(x, y) ((x) < (y) ? (x) : (y))
#define SUM(x, y) ((x) + (y))
当宏使用多个语句时，使用do-while(0)语句保护它
typedef struct {
int32_t px, py;
} point_t;
point_t p; /* Define new point */
/* Wrong implementation */
/* Define macro to set point */
#define SET_POINT(p, x, y) (p)->px = (x); (p)->py = (y) /* 2 statements. Last one should not implement semicolon */
SET_POINT(&p, 3, 4); /* Set point to position 3, 4. This evaluates to... */
(&p)->px = (3); (&p)->py = (4); /* ... to this. In this example this is not a problem. */
/* Consider this ugly code, however it is valid by C standard (not recommended) */
if (a) /* If a is true */
if (b) /* If b is true */
SET_POINT(&p, 3, 4);/* Set point to x = 3, y = 4 */
else
SET_POINT(&p, 5, 6);/* Set point to x = 5, y = 6 */
/* Evaluates to code below. Do you see the problem? */
if (a)
if (b)
(&p)->px = (3); (&p)->py = (4);
else
(&p)->px = (5); (&p)->py = (6);
/* Or if we rewrite it a little */
if (a)
if (b)
(&p)->px = (3);
(&p)->py = (4);
else
(&p)->px = (5);
(&p)->py = (6);
/*
* Ask yourself a question: To which `if` statement `else` keyword belongs?
*
* Based on first part of code, answer is straight-forward. To inner `if` statement when we check `b` condition
* Actual answer: Compilation error as `else` belongs nowhere
*/
/* Better and correct implementation of macro */
#define SET_POINT(p, x, y) do { (p)->px = (x); (p)->py = (y); } while (0) /* 2 statements. No semicolon after while loop */
/* Or even better */
#define SET_POINT(p, x, y) do { \ /* Backslash indicates statement continues in new line */
(p)->px = (x); \
(p)->py = (y); \
} while (0) /* 2 statements. No semicolon after while loop */
/* Now original code evaluates to */
if (a)
if (b)
do { (&p)->px = (3); (&p)->py = (4); } while (0);
else
do { (&p)->px = (5); (&p)->py = (6); } while (0);
/* Every part of `if` or `else` contains only `1` inner statement (do-while), hence this is valid evaluation */
/* To make code perfect, use brackets for every if-ifelse-else statements */
if (a) { /* If a is true */
if (b) { /* If b is true */
SET_POINT(&p, 3, 4);/* Set point to x = 3, y = 4 */
} else {
SET_POINT(&p, 5, 6);/* Set point to x = 5, y = 6 */
}
}
不缩进子语句内#if语句
/* OK */
#if defined(XYZ)
#if defined(ABC)
/* do when ABC defined */
#endif /* defined(ABC) */
#else /* defined(XYZ) */
/* Do when XYZ not defined */
#endif /* !defined(XYZ) */
/* Wrong */
#if defined(XYZ)
#if defined(ABC)
/* do when ABC defined */
#endif /* defined(ABC) */
#else /* defined(XYZ) */
/* Do when XYZ not defined */
#endif /* !defined(XYZ) */
文档
文档化的代码允许doxygen解析和通用的html/pdf/latex输出，因此正确地执行是非常重要的。
对变量、函数和结构/枚举使用doxygen支持的文档样式
经常使用\作为doxygen，不要使用@
始终使用5x4空格(5个制表符)作为文本行开始的偏移量
/**
* \brief Holds pointer to first entry in linked list
* Beginning of this text is 5 tabs (20 spaces) from beginning of line
*/
static
type_t* list;
每个结构/枚举成员都必须包含文档
注释的开头使用12x4空格偏移量
/**
* \brief This is point struct
* \note This structure is used to calculate all point
* related stuff
*/
typedef struct {
int32_t x; /*!< Point X coordinate */
int32_t y; /*!< Point Y coordinate */
int32_t size; /*!< Point size.
Since comment is very big,
you may go to next line */
} point_t;
/**
* \brief Point color enumeration
*/
typedef enum {
COLOR_RED, /*!< Red color. This comment has 12x4
spaces offset from beginning of line */
COLOR_GREEN, /*!< Green color */
COLOR_BLUE, /*!< Blue color */
} point_color_t;
函数的文档必须在函数实现中编写(通常是源文件)
函数必须包括简要和所有参数文档
如果每个参数分别为in或out输入和输出，则必须注意
如果函数返回某个值，则必须包含返回形参。这不适用于void函数
函数可以包含其他doxygen关键字，如note或warning
在参数名和描述之间使用冒号:
/**
* \brief Sum `2` numbers
* \param[in] a: First number
* \param[in] b: Second number
* \return Sum of input values
*/
int32_t
sum(int32_t a, int32_t b) {
return a + b;
}
/**
* \brief Sum `2` numbers and write it to pointer
* \note This function does not return value, it stores it to pointer instead
* \param[in] a: First number
* \param[in] b: Second number
* \param[out] result: Output variable used to save result
*/
void
void_sum(int32_t a, int32_t b, int32_t* result) {
*result = a + b;
}
如果函数返回枚举的成员，则使用ref关键字指定哪个成员
/**
* \brief My enumeration
*/
typedef enum {
MY_ERR, /*!< Error value */
MY_OK /*!< OK value */
} my_enum_t;
/**
* \brief Check some value
* \return \ref MY_OK on success, member of \ref my_enum_t otherwise
*/
my_enum_t
check_value(void) {
return MY_OK;
}
对常量或数字使用符号(' NULL ' => NULL)
/**
* \brief Get data from input array
* \param[in] in: Input data
* \return Pointer to output data on success, `NULL` otherwise
*/
const void *
get_data(const void* in) {
return in;
}
宏的文档必须包括hideinitializer doxygen命令
/**
* \brief Get minimal value between `x` and `y`
* \param[in] x: First value
* \param[in] y: Second value
* \return Minimal value between `x` and `y`
* \hideinitializer
*/
#define MIN(x, y) ((x) < (y) ? (x) : (y))
头/源文件
在文件末尾留下一个空行
每个文件都必须包括文件的doxygen注释和后跟空行的简要描述(使用doxygen时)
/**
* \file template.h
* \brief Template include file
*/
/* Here is empty line */
每个文件(头文件或源文件)必须包含许可证(开始注释包括单个星号，因为doxygen必须忽略这个)
使用与项目/库已经使用的相同的许可证
/**
* \file template.h
* \brief Template include file
*/
/*
* Copyright (c) year FirstName LASTNAME
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* This file is part of library_name.
*
* Author: FirstName LASTNAME <optional_email@example.com>
*/
头文件必须包含保护符#ifndef
头文件必须包含c++检查
在c++检查之外包含外部头文件
首先用STL C文件包含外部头文件，然后是应用程序自定义文件
头文件必须包含其他所有头文件，以便正确编译，但不能包含更多头文件(如果需要，.c应该包含其余的头文件)
头文件必须只公开模块公共变量/类型/函数
在头文件中使用extern作为全局模块变量，稍后在源文件中定义它们
/* file.h ... */
#ifndef ...
extern int32_t my_variable; /* This is global variable declaration in header */
#endif
/* file.c ... */
int32_t my_variable; /* Actually defined in source */
不要把.c文件包含在另一个.c文件中
.c文件应该首先包含相应的.h文件，然后是其他文件，除非另有明确的必要
在头文件中不包含模块私有声明
头文件示例(示例中没有license)
/* License comes here */
#ifndef TEMPLATE_HDR_H
#define TEMPLATE_HDR_H
/* Include headers */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/* File content here */
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* TEMPLATE_HDR_H */
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