C++ Coding Standards

References

Naming

General Naming Rules

int num_errors; // Good.

int num_completed_connections; // Good.

int n; // Bad - meaningless.

int nerr; // Bad - ambiguous abbreviation.

int n_comp_conns; // Bad - ambiguous abbreviation.

// Good

// These show proper names with no abbreviations.

int num_dns_connections; // Most people know what "DNS" stands for.

int price_count_reader; // OK, price count. Makes sense.

// Bad!

// Abbreviations can be confusing or ambiguous outside a small group.

int wgc_connections; // Only your group knows what this stands for.

int pc_reader; // Lots of things can be abbreviated "pc".

File Names

my_useful_class.cpp

my-useful-class.cpp

myusefulclass.cpp

myusefulclass_test.cpp // _unittest and _regtest are deprecated.

url_table.h // The class declaration.

url_table.cpp // The class definition.

url_table-inl.h // Inline functions that include lots of code.

Type Names

// classes and structs

class UrlTable { ...

class UrlTableTester { ...

struct UrlTableProperties { ...

// typedefs

typedef hash_map<UrlTableProperties *, string> PropertiesMap;

// enums

enum UrlTableErrors { ...

Variable Names

// Common Variable names

string table_name; // OK - uses underscore.

string tablename; // OK - all lowercase.

string tableName; // Bad - mixed case.

// Class Data Members

string _table_name; // OK - underscore at first.

string _tablename; // OK.

Constant Names

const int DAYSINWEEK = 7; // OK - all uppercase.

Function Names

// Regular Functions

AddTableEntry()

DeleteUrl()

OpenFileOrDie()

// Accessors and Mutators

class MyClass

{

public:

MyClass()

{

}

~MyClass()

{

}

int get_num_entries() const

{

return _num_entries;

}

void set_num_entries(int num_entries)

{

_num_entries = num_entries;

}

private:

int _num_entries;

};

Macro Names

#define ROUND(x) ...

#define PI_ROUNDED 3.0

Formatting

Line Length

Each line of text in your code should be at most 80 characters long.

Non-ASCII Characters
Spaces vs. Tabs

Indent 4 spaces at a time.

Function Declarations and Definitions

Return type on the same line as function name, parameters on the same line if they fit.

// Functions look like this:

ReturnType ClassName::FunctionName(Type par_name1, Type par_name2)

{

DoSomething();

...

}

// If you have too much text to fit on one line:

ReturnType ClassName::ReallyLongFunctionName(Type par_name1, Type par_name2,

Type par_name3)

{

DoSomething();

...

}

// or if you cannot fit even the first parameter:

ReturnType LongClassName::ReallyReallyReallyLongFunctionName(

Type par_name1, // 4 space indent

Type par_name2,

Type par_name3)

{

DoSomething(); // 4 space indent

...

}

// Everything in this function signature fits on a single line

ReturnType FunctionName(Type par) const

{

...

}

// This function signature requires multiple lines, but

// the const keyword is on the line with the last parameter.

ReturnType ReallyLongFunctionName(Type par1,

Type par2) const

{

...

}

// Always have named parameters in interfaces.

class Shape

{

public:

virtual void Rotate(double radians) = 0;

}

// Always have named parameters in the declaration.

class Circle : public Shape

{

public:

virtual void Rotate(double radians);

}

// Comment out unused named parameters in definitions.

void Circle::Rotate(double /*radians*/) {}

// Bad - if someone wants to implement later, it's not clear what the

// variable means.

void Circle::Rotate(double) {}

Function Calls

On one line if it fits; otherwise, wrap arguments at the parenthesis.

//Function calls have the following format:

bool retval = DoSomething(argument1, argument2, argument3);

// If the arguments do not all fit on one line, they should be broken up onto multiple lines,

// with each subsequent line aligned with the first argument.

// Do not add spaces after the open paren or before the close paren:

bool retval = DoSomething(averyveryveryverylongargument1,

argument2, argument3);

// If the function has many arguments, consider having one per line

bool retval = DoSomething(argument1,

argument2,

argument3,

argument4);

// If the function signature is so long that it cannot fit within the maximum line length

if (...)

{

...

if (...)

{

DoSomethingThatRequiresALongFunctionName(

very_long_argument1, // 4 space indent

argument2,

argument3,

argument4);

}

Conditionals

if (condition) // no spaces inside parentheses

{

... // 4 space indent.

}

else if (...) // The else goes on the new line

{

...

}

else

{

...

}

if(condition) // Bad - space missing after IF.

if(condition){ // Doubly bad.

// Short conditional statements still need the parentheses

if (x == kFoo)

{

return new Foo();

}

// Not allowed - if statement on one line when there is an else clause

if (x) DoThis();

else DoThat();

Loops and Switch Statements

switch (var)

{

case 0:

{

... // 4 space indent

break;

}

case 1:

{

...

break;

}

default:

{

assert(false);

}

// Empty loop bodies should use {}, but not a single semicolon.

while (condition)

{

// Repeat test until it returns false.

}

for (int i = 0; i < kSomeNumber; ++i)

{

} // Good - empty body.

while (condition); // Bad - looks like part of do/while loop.

Pointer and Reference Expressions

// No spaces around period or arrow. Pointer operators do not have trailing spaces.

x = *p;

p = &x;

x = r.y;

x = r->y;

// These are fine, space preceding.

char *c;

const string &str;

// These are fine, space following.

char* c; // but remember to do "char* c, *d, *e, ...;"!

const string& str;

char * c; // Bad - spaces on both sides of *

const string & str; // Bad - spaces on both sides of &

Boolean Expressions

if (this_one_thing > this_other_thing &&

a_third_thing == a_fourth_thing &&

yet_another && last_one)

{

...

}

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C++ Coding Standards

References

Naming

Formatting

Header Files

Classes

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