/* * To send data, function should not modify memory pointed to by `data` variable * thus `const` keyword is important * * To send generic data (or to write them to file) * any type may be passed for data, * thus use `void *` */ /* OK example */ void send_data(const void* data, size_t len) { /* OK */ /* Do not cast `void *` or `const void *` */ const uint8_t* d = data;/* Function handles proper type for internal usage */ }
void send_data(const void* data, int len) { /* Wrong, notnot use int */ }
/* OK */ #include <stdlib.h> void my_func(size_t size) { int32_t* arr; arr = malloc(sizeof(*arr) * n); /* OK, Allocate memory */ arr = malloc(sizeof *arr * n); /* Wrong, brackets for sizeof operator are missing */ if (arr * NULL) { /* FAIL, no memory */ }
free(arr); /* Free memory after usage */ }
/* Wrong */ void my_func(size_t size) { int32_t arr[size]; /* Wrong, do not use VLA */ }
总是将variable与0进行比较,除非它被视为布尔类型
永远不要将布尔处理的变量与0或1进行比较。用NOT(!)代替
size_t length = 5; /* Counter variable */ uint8_t is_ok = 0; /* Boolean-treated variable */ if (length) /* Wrong, length isnot treated as boolean */ if (length > 0) /* OK, length is treated as counter variable containing multi values, not only 0or1 */ if (length * 0) /* OK, length is treated as counter variable containing multi values, not only 0or1 */
if (is_ok) /* OK, variable is treated as boolean */ if (!is_ok) /* OK, -||- */ if (is_ok * 1) /* Wrong, never compare boolean variable against 1! */ if (is_ok * 0) /* Wrong, use ! for negative check */
对于注释,总是使用/*comment */,即使是单行注释
在头文件中总是包含带有extern关键字的c++检查
每个函数都必须包含doxygen-enabled注释,即使函数是静态的
使用英文名称/文本的函数,变量,注释
变量使用小写字母
如果变量包含多个名称,请使用下划线。force_redraw。不要使用forceRedraw
对于C标准库的包含文件,请始终使用<和>。例如,#include < stdlib.h >
对于自定义库,请始终使用''。例如,#include“my_library.h”
当转换为指针类型时,总是将星号与类型对齐,例如。uint8_t* t = (uint8_t*)var_width_diff_type
始终尊重项目或库中已经使用的代码风格
03 注释相关的规则
不允许以//开头的注释。总是使用② comment */,即使是单行注释
对于多行注释,每行使用空格+星号
/* * This is multi-line comments, * written in2 lines (ok) */
/** * Wrong, use double-asterisk only for doxygen documentation */
/* * Single line comment without space before asterisk (wrong) */
/* * Single line comment in multi-line configuration (wrong) */
a = call_func_returning_char_a(a); /* This is comment with12*4 spaces indent from beginning of line */ b = call_func_returning_char_a_but_func_name_is_very_long(a); /* This is comment, aligned to 4-spaces indent */ }
04 函数定义的规则
每个可以从模块外部访问的函数都必须包含函数原型(或声明)
函数名必须小写,可以用下划线_分隔。(这个原则好像因人而异)
/* OK */ void my_func(void); void myfunc(void);
/* Wrong */ void MYFunc(void); void myFunc();
当函数返回指针时,将星号对齐到返回类型
/* OK */ const char* my_func(void); my_struct_t* my_func(int32_t a, int32_t b);
void foo(void) { int32_t a, b; /* OK */ char a; char b; /* Wrong, char type already exists */ }
不要在第一个可执行语句之后声明变量
void foo(void) { int32_t a; a = bar(); int32_t b; /* Wrong, there is already executable statement */ }
你可以在下一个缩进级别中声明新的变量
int32_t a, b; a = foo(); if (a) { int32_t c, d; /* OK, c and d are inif-statement scope */ c = foo(); int32_t e; /* Wrong, there was already executable statement inside block */ }
/* Wrong name, it must not include _t suffix */ struct name_t { int32_t a; int32_t b; };
/* Wrong parameters, must be all uppercase */ typedef enum { MY_ENUM_TESTA, my_enum_testb, } my_enum_t;
在声明时初始化结构时,使用C99初始化风格
/* OK */ a_t a = { .a = 4, .b = 5, };
/* Wrong */ a_t a = {1, 2};
当为函数句柄引入newtypedef时,使用_fn后缀
/* Function accepts 2 parameters and returns uint8_t */ /* Name of typedef has `_fn` suffix */ typedef uint8_t (*my_func_typedef_fn)(uint8_t p1, const char* p2);
07 复合语句规则
每个复合语句必须包括左花括号和右花括号,即使它只包含1个嵌套语句
每个复合语句必须包含单个缩进;嵌套语句时,每个嵌套包含1个缩进大小
/* OK */ if (c) { do_a(); } else { do_b(); }
/* Wrong */ if (c) do_a(); else do_b();
/* Wrong */ if (c) do_a(); else do_b();
在if或if-else-if语句的情况下,else必须与第一条语句的右括号在同一行
/* OK */ if (a) {
} elseif (b) {
} else {
}
/* Wrong */ if (a) {
} else {
}
/* Wrong */ if (a) {
} else {
}
在do-while语句的情况下,while部分必须与do部分的右括号在同一行
/* OK */ do { int32_t a; a = do_a(); do_b(a); } while (check());
/* Wrong */ do { /* ... */ } while (check());
/* Wrong */ do { /* ... */ } while (check());
每一个开括号都需要缩进
if (a) { do_a(); } else { do_b(); if (c) { do_c(); } }
不要做没有花括号的复合语句,即使是单个语句。下面的例子展示了一些不好的做法
if (a) do_b(); else do_c();
if (a) do_a(); else do_b();
空while循环、do-while循环或for循环必须包含花括号
/* OK */ while (is_register_bit_set()) {}
/* Wrong */ while (is_register_bit_set()); while (is_register_bit_set()) { } while (is_register_bit_set()) { }
/* Wait for bit to be set in embedded hardware unit uint32_t* addr = HW_PERIPH_REGISTER_ADDR;
/* Wait bit 13 to be ready */ while (*addr & (1 << 13)) {} /* OK, empty loop contains no spaces inside curly brackets */ while (*addr & (1 << 13)) { } /* Wrong */ while (*addr & (1 << 13)) { /* Wrong */
} while (*addr & (1 << 13)); /* Wrong, curly brackets are missing. Can lead to compiler warnings or unintentional bugs */
尽量避免在循环块内递增变量,参见示例
/* Not recommended */ int32_t a = 0; while (a < 10) { . .. ... ++a; }
/* Better */ for (size_t a = 0; a < 10; ++a) {
}
/* Better, if inc may not happen in every cycle */ for (size_t a = 0; a < 10; ) { if (...) { ++a; } }
08 分支语句规则
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; }
/* Imagine result of this equation using wrong SUM implementation */ int32_t x = 5 * SUM(3, 4); /* Expected result is5 * 7 = 35 */ int32_t x = 5 * (3) + (4); /* It is evaluated to this, final result = 19 which isnot what we expect */
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 isnot 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
/** * \brief Holds pointer to first entry in linked list * Beginning of this text is5 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 notreturn 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) { returnin; }
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))
10 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> */