Coding Standard - PLLUG/CPPQT-2019-1-FileServer GitHub Wiki

Coding Standard

1. Identation, Code Formatting, Editor Settings

1.1 Identation Rules

Ident.1 Spaces should be used everywhere as indentation symbol. Spaces not tabs!
Ident.2 Use 4 spaces to indent code.
{
    // code line 1
    // code line 2
    {
        // inner block
        // 
    }
}
Ident.3 One indent should be placed before new line.
if (longExpression
    + otherLongExpression
    + otherOtherLongExpression)
{
}

1.2 Line breaks

Breaks.1 Keep lines shorter than 100 characters; insert line breaks if necessary.
Breaks.2 Operators start at the beginning of the new line.
if (longExpression
    + otherLongExpression
    + otherOtherLongExpression)
{
}

1.3 Whitespaces

Spaces.1 Always use blank lines to group statements together where suited. Always use only one blank line.
Spaces.2 Always use a single space after a keyword, and before a curly brace.
if (foo)
{
}
Spaces.3 For pointers or references, always use a single space between the type and * or &, but no space between the * or & and the variable name.
Spaces.4 No space is allowed between return type and * or & in function/method definitions/declarations.
Spaces.5 No space is allowed between function/method name and braces in function/method definitions/declarations/call.
const char* ch;
const void *const someConstant;
std::string &str = someString;
char* func1();
Spaces.6 No space after a cast.
char *blockOfMemory = reinterpret_cast<char*>(malloc(data.size()));

1.4 Braces

Braces.1 Always use a new line for open/closed curly brace
if (foo)
{
}
Braces.2 Always use curly braces with conditional statements, even if it contains only one line.
// Wrong
if (address.isEmpty())
return false;
 
// Wrong
for (int i = 0; i < 10; ++i) qDebug("%i", i);
 
// Correct
if (address.isEmpty())
{
    return false;
}

1.5 IDE Editor Settings

IDE.1 Make Qt Creator follow identation rules. Use editor settings. Recommended settings see below.
[%General]
DefaultFileEncoding=@ByteArray(UTF-8)
 
[textMarginSettings]
MarginColumn=100
ShowMargin=true
 
[textStorageSettings]
addFinalNewLine=true
cleanIndentation=true
cleanWhitespace=true
inEntireDocument=true
 
[textTabPreferences]
AutoSpacesForTabs=false
IndentSize=4
PaddingMode=1
SpacesForTabs=true
TabSize=4
 
[textTypingSettings]
AutoIndent=true
SmartBackspaceBehavior=1
TabKeyBehavior=0

2. Statements, Expressions, Operations

2.1 Expressions

Expr.1 Use parentheses to group expressions.
// Wrong
if (a && b || c)
 
// Wrong
a + b & c
 
// Correct
if ((a && b) || c)
 
// Correct
(a + b) & c

2.2 Statements

Stat.1 The case labels are on the same column as the switch.
Stat.2 Every case block has identation. break or return should have same identation as case block.
Stat.3 Every case must have a break (or return) statement at the end or a comment to indicate that there’s intentionally no break.
switch (myEnum)
{
case Value1:
 doSomething();
 break;

case Value2:
 // nothing
 break;

default:
 defaultHandling();
 break;
}

3 Types, Variables, Declatation and Initialization

3.1 Variable and Type Naming Conventions

Name.1 Use camel case style for names (e. g. each consecive word in a name starts with a capital letter)
Name.2 Variables, functions and methods names must start with a small letter.
Name.3 Add 'g' prefix to global variables.
Name.4 Add 'm' prefix to class and structure members.
Name.5 Add 'pr' prefix to function or method parameters used to return value.
Name.6 Add 'r' prefix to variables that will be returned from function or method.
Name.7 Add 'c' prefix to constants.
Name.8 Add 's' prefix to static variables and class/structure members.
Name.9 Local variables and function/method parameters that are not static or constant and do not return value from function/method - has no prefix.
Name.9 Class and structure names always start with big letters.
Name.10 Namespace names always start with big letters.
Name.11 Enum names starts with big letters. Start every enum with a big letter.
Name.12 Use only upper case letters and _ symbol as a word separator for macros names.

3.2 Variable Declarations and Initialization

Var.1 Declare each variable on a separate line.
Var.2 Avoid abbraviations, short, unclear or hard to understand/remember variable names whenever possible.
Var.3 Single character variable names are only okay for counters, where the purpose of the variable is obvious or in math calculation (only when meaning of variable is obvious).
// Wrong
int a, b;
char *c, *d;
int foo;
int bar, baz;
void *scsdSgPtr;
char *Var, VAR;
 
// Correct
int height;
int width;
char *userName;
QHash<int, QString> mNameByIndex;
QWidget *mTimeDisplayWidget;
QTimer mRequestTimeoutTimer;
for (int i = 0; i < count; ++i) {.....}
while (k < count) {++k}
Var.4 Use initializer lists wherever possible. Skip = when using {}-initializer.
Var.5 Use auto only for local variables where precision or range should not be specified explicitly.
// Not desirable 
int i = 1.02; // Narrowing
int i = {1} ;
 
// Right
int i {1}; // Also saves from narrowing
QList<QString> vegetables{"potato", "tomato", "cabbage"};
 
auto i = 0;
Var.6. Wait with declaring a variable until it is needed.
Var.7. Make variable lifetime and visibility scope as short as possible.

3.3 Type Declarations

Type.1 Use strongly typed enums (enum classes) as much as possible.
enum class TrafficLightColors {Red, Green, Blue}

4. Coding Documentation

4.1 Comments

Comment.1 Use Doxygen style of code documentation.

5. Coding Guidelines

Here will be rules in addition to CPP Core Guidelines.

6. Project Structure

6.1 File Naming

File.1 All headers and source files should be named in lowercase.
File.2 In general: no underscore sumbols “_” as separators between words.
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