C++ Coding Standards

Last Update: 2024-08-09

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Preface

Rule of Thumb

Readability first (your code should be your documentation most of the time)
Crash/Assert early. Don't wait until the worst case happens to make the crash condition.
Follow IDE's auto formatted style unless you have really good reasons not to do so. (Ctrl + K + D in VC++)
Learn from existing code

References

This coding standards is inspired by these coding standards

I. Main Coding Standards

Use Pascal casing for class and structs

 class PlayerManager;
 struct AnimationInfo;

Use camel casing for local variable names and function parameters

 void SomeMethod(const int someParameter);
 {
     int someNumber;
     int id;
 }

Use verb-object pairs for method names

a. Use pascal casing for public methods
```
 public:
     void DoSomething();
```
b. Use camel casing for other methods
```
 private:
     void doSomething();
```

However, if a method simply returns a boolean state, the verb part of the name should be prefixed Is, Can, Has or Should. If the function name becomes not natural by doing so, use the 3rd-person singular form of another verb.

 public:
     bool IsAlive(const Person& person) const;
     bool HasChild(const Person& person) const;
     bool CanAccept(const Person& person) const;
     bool ShouldDelete(const Person& person) const;
     bool Exists(Person& person) const;

Use ALL_CAPS_SEPARATED_BY_UNDERSCORE for constants and defines
```
 constexpr int SOME_CONSTANT = 1;
```
Use all lowercase letters for namespaces
```
 namespace abc{};
```

prefix boolean variables with b

 bool bFired;	// for local and public member variable
 bool mbFired;	// for private class member variable

prefix interfaces with I
```
 class ISomeInterface;
```

prefix enums with e

 enum class eDirection
 {
     North,
     South
 }

prefix class member variables with m.

 class Employee
 {
 protected:
     int mDepartmentID;
 private:
     int mAge;
 }

Use ALL_CAPS_SEPARATED_BY_UNDERSCORE for goto labels.

 goto MY_LABEL;


 // ....

 MY_LABEL:
     std::cout << "Magic!" << std::endl;
     return 0;

Methods with return values must have a name describing the value returned
```
uint32_t GetAge() const;
```
Use descriptive variable names. e.g index or employee instead of i or e unless it is a trivial index variable used for loops.
Capitalize every characters in acronyms only if there is no extra word after them.
```
int OrderID;
int HttpCode;
```

Always use setter and getters for class member variables

Use:

class Employee
{
public:
    const string& GetName() const;
    void SetName(const string& name);
private:
    string mName;
}

Instead of:

class Employee
{
public:
    string Name;
}

Use only public member variables for a struct. No functions are allowed. Use pascal casing for the members of a struct.
```
struct MeshData
{
    int32_t VertexCount;
}
```
Use #include<> for external header files. Use #include "" for in-house header files
Put external header files first, followed by in-house header files in alphabetic order if possible.
```
#include <vector>
#include <unordered_map>

#include "AnimationInfo.h"
```
Use #pragma once at the beginning of every header file
Declare local variables as close as possible to the first line where it is being used.
Use precision specification for floating point values unless there is an explicit need for a double
```
float f = 0.5f;
```

Always have a default case for a switch statement.

switch (number)
{
case 0:
    ... 
    break;
default:
    break;
}

Always add predefined FALLTHROUGH for switch case fall through unless there is no code in the case statement. This will be replaced by [[fallthrough]] attribute coming in for C++17 later
```
switch (number)
{
case 0:
    DoSomething();
    FALLTHROUGH
case 1:
    DoFallthrough();
    break;
case 2:
case 3:
    DoNotFallthrough();
    break;
default:
    break;
}
```
If default case must not happen in a switch case, always add Assert(false). In our assert implementation, this will add optimization hint for release build.
```
switch (type)
{
case 1:
    ... 
    break;
default:
    Assert(false, "unknown type");
    break;
}
```
Use consts as much as possible even for local variable and function parameters.
Any member functions that doesn't modify the object must be const
```
int GetAge() const;
```
Do not return const value type. Const return is only for reference and pointers
Names of recursive functions end with Recursive.
```
void FibonacciRecursive();
```
Order of class variables and methods must be as follows:

a. list of friend classes b. public methods c. protected methods d. private methods e. protected variables f. private variables

Function overloading must be avoided in most cases

Use:

const Anim* GetAnimByIndex(const int index) const;
const Anim* GetAnimByName(const char* name) const;

Instead of:

const Anim* GetAnim(const int index) const;
const Anim* GetAnim(const char* name) const;

Overloading functions to add const accessible function is allowed.

Anim* GetAnimByIndex(const int index);
const Anim* GetAnimByIndex(const int index) const;

Avoid use of const_cast. Instead create a function that clearly returns an editable version of the object
Each class must be in a separate source file unless it makes sense to group several smaller classes.
The filename must be the same as the name of the class including upper and lower cases.
```
class PlayerAnimation;

PlayerAnimation.cpp
PlayerAnimation.h
```
When a class spans across multiple files, these files have a name that starts with the name of the class, followed by an underscore and the subsection name.
```
class RenderWorld;

RenderWorld_load.cpp
RenderWorld_demo.cpp
RenderWorld_portals.cpp
```

Platform specific class for reverse OOP pattern uses similar naming convention

class Renderer;

Renderer.h		// all renderer interfaces called by games
Renderer.cpp	// Renderer's Implementations which are
            // to all platforms
Renderer_gl.h	// RendererGL interfaces called by
            // Renderer
Renderer_gl.cpp	// RendererGL implementations

Use our own version of Assert instead of standard c assert
Use assert for any assertion you have. Assert is not recoverable. This can be replaced by compiler optimization hint keyword __assume for the release build.
Any memory allocation must be done through our own New and Delete keyword.
Memory operations such as memset, memcpy and memmove also must be done through our own MemSet, MemCpy and MemMove.
Generally prefer reference(&) over pointers unless you need nullptr for any reason. (exceptions are mentioned right below)

Use pointers for out parameters. Also prefix the function parameters with out.

function:

void GetScreenDimension(uint32_t* const outWidth, uint32_t* const  outHeight)
{
}

caller:

uint32_t width;
uint32_t height;
GetScreenDimension(&width, &height);

The above out parameters must not be null. (Use assert, not if statement)

void GetScreenDimension(uint32_t* const outWidth, uint32_t* const  outHeight)
{
    Assert(outWidth);
    Assert(outHeight);
}

Use pointers if the parameter will be saved internally.

void AddMesh(Mesh* const mesh)
{
    mMeshCollection.push_back(mesh);
}

Use pointers if the parameter should be generic void* parameter
```
void Update(void* const something)
{
}
```
The name of a bitflag enum must be suffixed by Flags
```
enum class eVisibilityFlags
{
}
```
Do not add size specifier for enum unless you need that specific size (e.g, for serialization of data members)
```
enum class eDirection : uint8_t
{
    North,
    South
}
```
Prefer overloading over default parameters
When default parameters are used, restrict them to natural immutable constants such as nullptr, false or 0.
Prefer fixed-size containers whenever possible.
reserve() dynamic containers whenever possible
Always put parentheses for defined numbers
```
#define NUM_CLASSES (1)
```
Prefer constants over defines
Always use forward declaration if possible instead of using includes
All compiler warnings must be addressed.

Shadowed variables are not allowed.

class SomeClass
{
public:
    int32_t Count;
public:
    void Func(const int32_t Count)
    {
        for (int32_t count = 0; count != 10; ++count)
        {
            // Use Count
        }
    }
}

Declare only one variable per line

BAD:

int counter, index;

GOOD:

int counter;
int index;

Take advantage of NRVO, when you are returning a local object. This means you need to have only one return statement inside your function. This applies only when you return an object by value.
Do not use const member variables in a struct or class simply to prevent modification after initialization. Same rule is applied to reference(&) member variables.
When initializing member variables, use initializer list over assignments, by default.
«<__restrict keyword

II. Code Formatting

There must be a blank line between includes and body.
Use Visual Studio default for tabs. If you are not using Visual Studio, use real tabs that are equal to 4 spaces.
Always place an opening curly brace ({) in a new line
Add curly braces even if there's only one line in the scope
```
 if (bSomething)
 {
     return;
 }
```
Put pointer or reference sign right next to the type
```
 int& number;
 int* number;
```

When initializing member variables via initializer list, initialize one member variable per line and follow below format.

BAD:

 MyClass::MyClass(const int var1, const int var2)
     :mVar1(var1), mVar2(var2), mVar3(0)
 {

GOOD:

 MyClass::MyClass(const int var1, const int var2)
     : mVar1(var1)
     , mVar2(var2)
     , mVar3(0)
     {

III. Modern Language Features

override and final keywords are mandatory

Use enum class always

 enum class eDirection
 {
     North,
     South
 }

Use static_assert over Assert, if possible.
Use nullptr over NULL
Use unique_ptr when a object lifetime is solely handled inside a class. (i.e. new in constructor delete in destructor)
Range-based for are recommended where applicable
Do not use auto unless it is for a iterator or new keyword is on the same line, showing which object is created clearly
Do not manually perform return value optimization using std::move. It breaks automatic NRVO optimization.
Move constructor and move assignment operator are allowed.

Use constexpr instead of const for simple constant variables

constexpr int DEFAULT_BUFFER_SIZE = 65536

Instead of

const int DEFAULT_BUFFER_SIZE = 65536

«<TBD: constexpr
«<TBD: Lambda
«<TBD: do not use shared_ptr

IV. Project Settings and Project Structure

Visual C++: Always use property sheets to change project settings
Do not disable compile warnings in project settings. Use #pragma in code instead.