編寫代碼時最重要的一條規(guī)則是：檢查周圍的代碼并嘗試模仿它。
作為維護人員，如果收到的補丁明顯與周圍代碼的編碼風格不同，這是令人沮喪的。這是不尊重人的，就像某人穿著泥濘的鞋子走進一間一塵不染的房子。
因此，無論本文推薦的是什么，如果已經(jīng)編寫了代碼并且您正在對其進行修補，請保持其當前的樣式一致，即使它不是您最喜歡的樣式。
這里列出了最明顯和最重要的一般規(guī)則。在你繼續(xù)閱讀其他章節(jié)之前，請仔細檢查它們。
int32_t a = sum(4, 3); /* OK */int32_t a = sum (4, 3); /* Wrong */size_t i;for (i = 0; i < 5; ++i) { /* OK */}for (i = 0; i < 5; ++i){ /* Wrong */}for (i = 0; i < 5; ++i) /* Wrong */{}// 微信公眾號：嵌入式大雜燴int32_t a;a = 3 + 4; /* OK */for (a = 0; a < 5; ++a) /* OK */a=3+4; /* Wrong */a = 3+4; /* Wrong */for (a=0;a<5;++a) /* Wrong */// 微信公眾號：嵌入式大雜燴func_name(5, 4); /* OK */func_name(4,3); /* Wrong */static int32_t a; /* OK */static int32_t b = 4; /* OK */static int32_t a = 0; /* Wrong */voidmy_func(void) { static int32_t* ptr;/* OK */ static char abc = 0;/* Wrong */}voidmy_func(void) { char a; /* OK */ char b; /* Wrong, variable with char type already exists */ char a, b; /* OK */}i.自定義結(jié)構(gòu)和枚舉
ii.整數(shù)類型，更寬的無符號類型優(yōu)先
iii.單/雙浮點
intmy_func(void) { /* 1 */ my_struct_t my; /* First custom structures */ my_struct_ptr_t* p; /* Pointers too */ /* 2 */ uint32_t a; int32_t b; uint16_t c; int16_t g; char h; /* ... */ /* 3 */ double d; float f;}/* OK */for (size_t i = 0; i < 10; ++i)/* OK, if you need counter variable later */size_t i;for (i = 0; i < 10; ++i) { if (...) { break; }}if (i == 10) {}/* Wrong */size_t i;for (i = 0; i < 10; ++i) ...voida(void) { /* Avoid function calls when declaring variable */ int32_t a, b = sum(1, 2); /* Use this */ int32_t a, b; b = sum(1, 2); /* This is ok */ uint8_t a = 3, b = 4;}/* OK */uint8_t status;status = 0;/* Wrong */#include <stdbool.h>bool status = true;void* ptr;/* ... *//* OK, compare against NULL */if (ptr == NULL || ptr != NULL) {}/* Wrong */if (ptr || !ptr) {}int32_t a = 0;...a++; /* Wrong */++a; /* OK */for (size_t j = 0; j < 10; ++j) {} /* OK *//* When d could be modified, data pointed to by d could not be modified */voidmy_func(const void* d) {}/* When d and data pointed to by d both could not be modified */voidmy_func(const void* const d) {}/* Not required, it is advised */voidmy_func(const size_t len) {}/* When d should not be modified inside function, only data pointed to by d could be modified */voidmy_func(void* const d) {}/* * 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 */voidsend_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 */}voidsend_data(const void* data, int len) { /* Wrong, not not use int */}/* OK */#include <stdlib.h>voidmy_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 */voidmy_func(size_t size) { int32_t arr[size]; /* Wrong, do not use VLA */}size_t length = 5; /* Counter variable */uint8_t is_ok = 0; /* Boolean-treated variable */if (length) /* Wrong, length is not treated as boolean */if (length > 0) /* OK, length is treated as counter variable containing multi values, not only 0 or 1 */if (length == 0) /* OK, length is treated as counter variable containing multi values, not only 0 or 1 */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 *///This is comment (wrong)/* This is comment (ok) *//* * This is multi-line comments, * written in 2 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) *//* Single line comment (ok) */voidmy_func(void) { char a, b; a = call_func_returning_char_a(a); /* This is comment with 12*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 */}/* OK */void my_func(void);void myfunc(void);/* Wrong */void MYFunc(void);void myFunc();/* OK */const char* my_func(void);my_struct_t* my_func(int32_t a, int32_t b);/* Wrong */const char *my_func(void);my_struct_t * my_func(void);/* OK, function names aligned */void set(int32_t a);my_type_t get(void);my_ptr_t* get_ptr(void);/* Wrong */void set(int32_t a);const char * get(void);/* OK */int32_tfoo(void) { return 0;}/* OK */static const char*get_string(void) { return 'Hello world!\r\n';}/* Wrong */int32_t foo(void) { return 0;}/* OK */int32_t a;int32_t my_var;int32_t myvar;/* Wrong */int32_t A;int32_t myVar;int32_t MYVar;voidfoo(void) { int32_t a, b; /* OK */ char a; char b; /* Wrong, char type already exists */}voidfoo(void) { int32_t a; a = bar(); int32_t b; /* Wrong, there is already executable statement */}int32_t a, b;a = foo();if (a) { int32_t c, d; /* OK, c and d are in if-statement scope */ c = foo(); int32_t e; /* Wrong, there was already executable statement inside block */}/* OK */char* a;/* Wrong */char *a;char * a;/* OK */char *p, *n;在聲明結(jié)構(gòu)體時，它可以使用以下三種不同的選項之一:
1、當結(jié)構(gòu)體僅用名稱聲明時，它的名稱后不能包含_t后綴。
struct struct_name { char* a; char b;};2、當只使用typedef聲明結(jié)構(gòu)時，它的名稱后面必須包含_t后綴。
typedef struct { char* a; char b;} struct_name_t;3、當結(jié)構(gòu)用name和typedef聲明時，它不能包含t作為基本名稱，它必須在它的名稱后面包含t后綴作為typedef部分。
typedef struct struct_name { char* a; char b; char c;} struct_name_t;錯誤聲明的例子及其建議的糾正：
/* a and b must be separated to 2 lines *//* Name of structure with typedef must include _t suffix */typedef struct { int32_t a, b;} a;/* Corrected version */typedef struct { int32_t a; int32_t b;} a_t;/* 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;/* OK */a_t a = { .a = 4, .b = 5,};/* Wrong */a_t a = {1, 2};/* 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);/* OK */if (c) { do_a();} else { do_b();}/* Wrong */if (c) do_a();else do_b();/* Wrong */if (c) do_a();else do_b();/* OK */if (a) {} else if (b) {} else {}/* Wrong */if (a) {}else {}/* Wrong */if (a) {}else{}/* OK */do { int32_t a; a = do_a(); do_b(a);} while (check());/* Wrong */do{/* ... */} while (check());/* Wrong */do {/* ... */}while (check());if (a) { do_a();} else { do_b(); if (c) { do_c(); }}if (a) do_b();else do_c();if (a) do_a(); else do_b();/* 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 unituint32_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 *//* 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; }}/* 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;}/* OK */switch (var) { case 0: do_job(); break; default: break;}/* Wrong, default is missing */switch (var) { case 0: do_job(); break;}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;}/* OK */#define MY_MACRO(x) ((x) * (x))/* Wrong */#define square(x) ((x) * (x))/* OK */#define MIN(x, y) ((x) < (y) ? (x) : (y))/* Wrong */#define MIN(x, y) x < y ? x : y/* 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))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 */ }}/* 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) */文檔化的代碼允許doxygen解析和通用的html/pdf/latex輸出，因此正確地執(zhí)行是非常重要的。
/** * \brief Holds pointer to first entry in linked list * Beginning of this text is 5 tabs (20 spaces) from beginning of line */statictype_t* list;/** * \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;/** * \brief Sum `2` numbers * \param[in] a: First number * \param[in] b: Second number * \return Sum of input values */int32_tsum(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 */voidvoid_sum(int32_t a, int32_t b, int32_t* result) { *result = a + b;}/** * \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_tcheck_value(void) { return MY_OK;}/** * \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;}/** * \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))/** * \file template.h * \brief Template include file */ /* Here is empty line *//** * \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> *//* 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 *//* License comes here */#ifndef TEMPLATE_HDR_H#define TEMPLATE_HDR_H/* Include headers */#ifdef __cplusplusextern 'C' {#endif /* __cplusplus *//* File content here */#ifdef __cplusplus}#endif /* __cplusplus */#endif /* TEMPLATE_HDR_H */