C++
int32_t a = sum(4, 3);              /* OK /int32_t a = sum (4, 3);             / Wrong */

Plain Text
size_t i;
for (i = 0; i < 5; ++i) {           /* OK /
}
for (i = 0; i < 5; ++i){            / Wrong /
}
for (i = 0; i < 5; ++i)             / Wrong */
{
}

C++
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 */

Plain Text
func_name(5, 4);        /* OK /func_name(4,3);         / Wrong */

C++
static int32_t a;       /* OK /static int32_t b = 4;   / OK /static int32_t a = 0;   / Wrong /void my_func(void) {
    static int32_t ptr;/* OK /static char abc = 0;/ Wrong */
}

C++
void my_func(void) {
    char a;             /* OK /char b;             / Wrong, variable with char type already exists /char a, b;          / OK */
}

C++
int my_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;
}

Plain Text
/* 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) ...

C++
void a(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;
}

C++
/* OK /uint8_t status;
status = 0;

/ Wrong */#include <stdbool.h>bool status = true;

YAML
void* ptr;/* ... // OK, compare against NULL /if (ptr * NULL || ptr != NULL) {}/* Wrong */if (ptr || !ptr) {}

C++
int32_t a = 0;
...

a++;            /* Wrong /
++a;            / OK /for (size_t j = 0; j < 10; ++j) {}  / OK */

C++
/* 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) {

}

C++
/*
* 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, not not use int */
}

C++
/* 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 */
}

C++
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 */

Markdown
/*
* 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) */

C++
void my_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 */
}

C++
/* OK /void my_func(void);
void myfunc(void);

/ Wrong */void MYFunc(void);
void myFunc();

C++
/* 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);

C++
/* 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);

C++
/* OK /int32_t
foo(void) {
    return 0;
}

/ OK */static const char*
get_string(void) {
    return "Hello world!\r\n";
}

/* Wrong */int32_t foo(void) {
    return 0;
}

C++
/* OK /int32_t a;
int32_t my_var;
int32_t myvar;

/ Wrong */int32_t A;
int32_t myVar;
int32_t MYVar;

C++
void foo(void) {
    int32_t a, b;   /* OK /char a;
    char b;         / Wrong, char type already exists */
}

C++
void foo(void) {
    int32_t a;
    a = bar();
    int32_t b;      /* Wrong, there is already executable statement */
}

C++
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 */
}

C++
/* OK /char a;

/* Wrong */char *a;
char * a;

C++
/* OK */char *p, *n;

C++
struct struct_name {char* a;
    char b;
};

C++
typedef struct {char* a;
    char b;
} struct_name_t;

C++
typedef struct struct_name {char* a;
    char b;
    char c;
} struct_name_t;

C++
/* 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;

C++
/* OK /a_t a = {
    .a = 4,
    .b = 5,
};

/ Wrong */a_t a = {1, 2};

C++
/* 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);

Plain Text
/* OK /if (c) {
    do_a();
} else {
    do_b();
}

/ Wrong /if (c)
    do_a();
elsedo_b();

/ Wrong */if (c) do_a();
else do_b();

CSS
/* OK /if (a) {

} else if (b) {

} else {

}

/ Wrong /if (a) {

}
else {

}

/ Wrong */if (a) {

}
else
{

}

C++
/* OK /do {
    int32_t a;
    a = do_a();
    do_b(a);
} while (check());

/ Wrong /do
{
/ ... /
} while (check());

/ Wrong /do {
/ ... */
}
while (check());

Plain Text
if (a) {
    do_a();
} else {
    do_b();
    if (c) {
        do_c();
    }
}

Plain Text
if (a) do_b();
else do_c();

if (a) do_a(); else do_b();

C++
/* OK /while (is_register_bit_set()) {}

/ Wrong */while (is_register_bit_set());
while (is_register_bit_set()) { }
while (is_register_bit_set()) {
}

C++
/* 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 */

C++
/* 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;
    }
}

C++
/* 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;
}

C#
/* OK /switch (var) {
    case 0:
        do_job();
        break;
    default: break;
}

/ Wrong, default is missing */switch (var) {
    case 0:
        do_job();
        break;
}

C++
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;
}

Plain Text
/* OK /#define MY_MACRO(x)         ((x)  (x))

/* Wrong /#define square(x)           ((x)  (x))

C++
/* OK /#define MIN(x, y)           ((x) < (y) ? (x) : (y))/ Wrong */#define MIN(x, y)           x < y ? x : y

C++
/* 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))

Rust
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);
    elsedo { (&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 */
    }
}

C++
/* 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

C++
/**
* \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;

C++
/**
* \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;

C++
/**
* \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
/voidvoid_sum(int32_t a, int32_t b, int32_t* result) {
    *result = a + b;
}

C++
/**
* \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;
}

C++
/**
* \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;
}

Markdown
/**
* \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))

C++
/**
* \file            template.h
* \brief           Template include file
// Here is empty line */

Markdown
/**
* \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>
*/

C++
/* 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 */

C++
/* 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 */