1# Coding Standard for the ANGLE Project 2 3## Google Style Guide 4 5We generally use the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) as a basis for 6our Coding Standard, however we will deviate from it in a few areas, as noted 7below. 8 9Items marked {DEV} indicate a deviation from the Google guidelines. Items marked 10{DO} are reiterating points from the Google guidelines. 11 12Before you upload code to Gerrit, use `git cl format` to auto-format your code. 13This will catch most of the trivial formatting errors and save you time. 14 15### [Header Files](https://google.github.io/styleguide/cppguide.html#Header_Files) 16 17* We use **`.h`** for C++ headers. 18* {DEV} #define guards should be of the form: `<PATH>_<FILE>_H_`. (Compiler 19 codebase is varied, including `<PROJECT>_` makes the names excessively 20 long). 21 22### [Scoping](https://google.github.io/styleguide/cppguide.html#Scoping) 23 24* {DO} avoid globally scoped variables, unless absolutely necessary. 25 26### [Classes](https://google.github.io/styleguide/cppguide.html#Classes) 27 28* {DEV} Inherit (privately) from angle::NonCopyable helper class (defined in 29 common/angleutils.h) to disable default copy and assignment operators. 30 31### [Other C++ Features](https://google.github.io/styleguide/cppguide.html#Other_C++_Features) 32 33* {DO} avoid use of default arguments. 34* {DONT} use C++ exceptions, they are disabled in the builds and not caught. 35* {DO} use nullptr (instead of 0 or NULL) for pointers. 36* {DO} use size\_t for loop iterators and size values. 37* {DO} use uint8\_t pointers instead of void pointers to denote binary data. 38* {DO} use C++11/14/17 according to the 39 [Chromium C++ features guide](https://chromium.googlesource.com/chromium/src/+/main/styleguide/c++/c++-features.md). 40 41### [Naming](https://google.github.io/styleguide/cppguide.html#Naming) 42 43#### File Names 44 45* {DEV} Filenames should be all lowercase and can include underscores (`_`). 46 If the file is an implementation of a class, the filename may be capitalized 47 the same as the major class. 48* {DEV} We use .cpp (instead of .cc), .h and .inl (inlined files) for C++ 49 files and headers. 50 51#### Directory Names 52* Directory names should be all lowercase, unless following an externally 53 imposed capitalization (eg include/EGL, or src/libGLESv2, etc) 54 55#### Variable Names 56 57Use the following guidelines, they do deviate somewhat from the [Google 58guidelines](https://google.github.io/styleguide/cppguide.html#Naming). 59 60* Class and type names: start with capital letter and use CamelCase. 61* {DEV} Class member variables: use an **`m`** prefix instead of trailing 62underscore and use CamelCase. 63* Global variables (if they must be used): use a **`g`** prefix. 64* {DEV} Variable names: start with lower case and use CamelCase (chosen for consistency) 65* {DEV} Function names: Member functions start with lower case and use CamelCase. Non-member and static member functions start with capital letter and 66use CamelCase (chosen for consistency) 67* {DO} Constants: start with a **`k`** and use CamelCase 68* Namespaces: short names. use all lower case 69* {DEV} Enum Names: use strongly typed class enums when possible. Use CamelCase for class enum members. See [official docs][EnumsOfficial]. 70* Macros: all uppercase with underscores 71* Exceptions to naming: use common sense! 72 73[EnumsOfficial]: https://google.github.io/styleguide/cppguide.html#Enumerator_Names 74 75### [Comments](https://google.github.io/styleguide/cppguide.html#Comments) 76 77* {DO} read and follow Google's recommendations. 78* Each file **must** start with the following boilerplate notice: 79 80``` 81// 82// Copyright $YEAR The ANGLE Project Authors. All rights reserved. 83// Use of this source code is governed by a BSD-style license that can be 84// found in the LICENSE file. 85// 86``` 87 88* $YEAR should be set to the current year at the time a file is created, and not changed thereafter. 89 90### [Formatting](https://google.github.io/styleguide/cppguide.html#Formatting) 91 92* {DEV} Avoid excessively long lines. Please keep lines under 100 columns 93 long. 94* Use unix-style newlines. 95* {DO} use only spaces. No tab characters. Configure your editor to emit 96 spaces when you hit the TAB-key. 97* {DEV} indent 4 spaces at a time. 98* conditionals: place space outside the parenthesis. No spaces inside. 99* switch statements: use the output of `git cl format`. 100* class format(eg private, public, protected): indent by 2 spaces. Regular 101 4-space indent from the outer scope for declarations/definitions. 102* pointers and references: **`*`** and **`&`** tight against the variable 103* namespaces: are not indented. 104* extern code blocks: are not indented. 105* {DEV} braces should go on a separate line, except for functions defined in a 106 header file where the whole function declaration and definition fit on one 107 line. 108 109Examples: 110 111``` 112if (conditional) 113{ 114 stuff(); 115} 116else 117{ 118 otherstuff() 119} 120``` 121 122``` 123switch (conditional) 124{ 125 case foo: 126 dostuff(); 127 break; 128 case bar: 129 otherstuff(); 130 break; 131 default: 132 WTFBBQ(); 133} 134``` 135 136``` 137class MyClass : public Foo 138{ 139 public: 140 MyClass(); 141 ~MyClass() {}; 142 private: 143 DISALLOW_COPY_AND_ASSIGN(MyClass); 144}; 145``` 146 147``` 148char *c; 149const string &str; 150``` 151 152### [Exceptions to the Rules](https://google.github.io/styleguide/cppguide.html#Exceptions_to_the_Rules) 153 154* If modifying pre-existing code that does not match the standard, the altered 155 portions of the code should be changed to match the standard. 156 157### Generated Source Files 158 159Prefer storing generated sources as baked files in the repository. Avoid using 160GN actions to run Python scripts. 161 162**Definition:** 163 164Sometimes helper scripts can create compilable sources more easily from XML or 165JSON data sources than maintaining source files by hand. These scripts are often 166written in Python and output generated sources. 167 168**Decision** 169 170Storing generated sources in the repository makes integration easier for non-GN 171users. Python scripts can be expensive and slow to run at compile-time. 172Generated sources can be a pain point for messing up builds. 173 174It could be possible to solve the build clobbering problem. And we could replace 175Python with something faster. But to allow for easier integration with our tools 176and customers we should bake generated files into the repository. 177