# HG changeset patch
# User David Demelier <markand@malikania.fr>
# Date 1506065547 -7200
# Node ID 841e39c8aba481c0c93589b73ffd168403d04346
# Parent  8a5d022aa6d570ece4bb2d33e0fb1efcee08b50a
Misc: add STYLE_CPP.md

diff -r 8a5d022aa6d5 -r 841e39c8aba4 STYLE_CPP.md
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/STYLE_CPP.md	Fri Sep 22 09:32:27 2017 +0200
@@ -0,0 +1,367 @@
+Malikania Engine C++ CODING STYLE
+=================================
+
+Style
+-----
+
+  - Always use 4 spaces as indentation,
+  - Use UTF-8 charset,
+  - Use Unix line endings,
+  - Do not exceed 120 characters for lines of code,
+  - Do not exceed 80 characters for comments,
+  - Never write two blank consecutives blank lines,
+  - Do not use bad words.
+
+### Braces
+
+Braces follow the K&R style, they are never placed on their own lines except for
+function definitions.
+
+Do not put braces for single line statements except for clarity.
+
+    if (condition) {
+        apply();
+        add();
+    } else
+        ok();
+
+    if (condition)
+        validate();
+
+    if (foo) {
+        state = long + conditional + that + requires + several + lines +
+            to + complete;
+    }
+
+Functions require braces on their own lines.
+
+    void function()
+    {
+    }
+
+And a lambda has its braces on the same lines too:
+
+    sort([&] (auto&) {
+        return true;
+    });
+
+### Spaces
+
+Each reserved keyword (e.g. `if`, `for`, `while`) requires a single space before
+its argument.
+
+Normal function calls do not require it.
+
+    if (foo)
+        destroy(sizeof (int));
+
+### References and pointers
+
+References and pointers are always next to the type name and not the variable.
+
+    T& get(const std::string& name);
+
+    int* p = &x;
+
+### Naming
+
+  - English names,
+  - Member variables have trailing underscore (e.g foo\_bar\_),
+  - No hungarian notation.
+
+Everything is in `underscore_case` except template parameters and macros.
+
+    #if defined(FOO)
+    #   include <foo.hpp>
+    #endif
+
+    namespace baz {
+
+    class object {
+    private:
+        std::string name_;
+
+    public:
+        inline const std::string& name() const noexcept
+        {
+            return name_;
+        }
+    };
+
+    template <typename Archive>
+    void open(const Archive& ar)
+    {
+        bool is_valid = false;
+    }
+
+    } // !baz
+
+### Header guards
+
+Do not use `#pragma once`.
+
+Header guards are usually named **PROJECT_COMPONENT_FILENAME_HPP**.
+
+    #ifndef FOO_COMMON_UTIL_HPP
+    #define FOO_COMMON_UTIL_HPP
+
+    #endif // !FOO_COMMON_UTIL_HPP
+
+### Enums
+
+Enumerations constants are always defined in separate line to allow commenting
+them as doxygen.
+
+Enum class are encouraged.
+
+    enum class color {
+        blue,
+        red,
+        green
+    };
+
+### Files
+
+  - Use `.cpp` and `.hpp` as file extensions,
+  - Filenames are all lowercase.
+
+### Comments
+
+Avoid useless comments in source files. Comment complex things or why it is done
+like this. However any public function in the .hpp **must** be documented as
+doxygen without exception.
+
+    /*
+     * Multi line comments look like
+     * this.
+     */
+
+    // Short comment
+
+Use `#if 0` to comment blocks of code.
+
+#if 0
+    broken_stuff();
+#endif
+
+### Includes
+
+The includes should always come in the following order.
+
+  1. C++ headers
+  2. C header
+  3. Third party libraries
+  4. Application headers in ""
+
+    #include <cstring>
+    #include <cerrno>
+
+    #include <sys/stat.h>
+
+    #include <libircclient.h>
+
+    #include "foo.h"
+
+**Note**: always use C++ headers for C equivalent, stdio.h -> cstdio, etc.
+
+### Commit messages
+
+Commit messages are written using the following syntax:
+
+    Topic: short message less than 80 characters
+
+    Optional additional description if needed.
+
+Replace `Topic` with one of the following:
+
+  - **Client**: client library and executable,
+  - **CMake**: for the build system,
+  - **Common**: common library,
+  - **Docs**: for the documentation,
+  - **Misc**: for miscellaneous files,
+  - **Server**: server library and executable,
+  - **Tests**: for the unit tests.
+
+Programming
+-----------
+
+### C language
+
+Do not use old C stuff like `void *`, `srand/rand`, `printf` or anything that
+can be rewritten in modern C++.
+
+### RTTI
+
+Usage of `dynamic_cast` and `typeid` are completely disallowed in any shape of
+form.
+
+### Arguments
+
+It is recommended to pass parameters by value or const reference. Usage of
+non-const reference as output parameter is **discouraged** and should be avoided
+in many case because it does not allow chaining of expressions like:
+
+    std::cout << reverse(upper(clean("  hello world!  "))) << std::endl;
+
+If your function is designed to return a modified value passed as argument, it
+is better to take it by value and modify it directly.
+
+    std::string clean(std::string input)
+    {
+        if (!input.empty() && input.back() == '\r')
+            input.pop_back();
+
+        return input;
+    }
+
+Never pass primitive types as const value.
+
+### Assertions
+
+Use the `assert` macro from the cassert header file to verify programming
+errors.
+
+For example, you may use `assert` to verify that the developer access the data
+between the bounds of an array:
+
+    T& operator[](unsigned index)
+    {
+        assert(index < length_);
+
+        return data_[index];
+    }
+
+The `assert` macro is not meant to check that a function succeeded, this code
+must not be written that way:
+
+    assert(listen(10));
+
+### Exceptions
+
+You must use exceptions to indicate an error that was unexpected such as:
+
+  - Failing to open a file,
+  - I/O unexpected errors,
+  - Parsing errors,
+  - User errors.
+
+You may use the C++ standard exceptions defined in the stdexcept header but if
+you need to carry more data within your exception, you should derive from
+`std::exception`.
+
+### Error code
+
+You should not use error codes to indicate errors, instead use exceptions.
+Error codes are allowed in Boost.Asio though.
+
+### Free functions
+
+Basic utility functions should be defined in a namespace as a free function not
+as a static member function, we're doing C++ not Java.
+
+Example:
+
+    namespace util {
+
+    std::string clean(std::string input);
+
+    } // !util
+
+### Variables initialization
+
+Use parentheses to initialize non primitive types:
+
+    throw std::runtime_error("foo");
+
+    my_class obj("bar");
+
+Use brace initialization when you want to use an initializer list, type
+elision:
+
+    std::vector<int> v{1, 2, 3};
+
+    foo({1, 2});                    // type deduced
+
+    return { "true", false };       // std::pair returned
+
+Use the assignment for primitive types:
+
+    int x = 123;
+    bool is_valid = true;
+
+### Classes
+
+Classes are usually defined in the following order:
+
+  1. Public inner types (enums, classes),
+  2. Protected/private members
+  3. Public functions
+
+    class foo {
+    public:
+        enum class type {
+            a,
+            b
+        };
+
+    private:
+        int member_{0};
+
+    public:
+        void some_function();
+    };
+
+### Structs
+
+Do not use C structs unless you have very good reason to do so. If you want to
+pack some data, just use `class` and make all fields public.
+
+    class point {
+    public:
+        int x{0};
+        int y{0};
+    };
+
+### Return
+
+The preferred style is to return early in case of errors. That makes the code
+more linear and not highly indented.
+
+This code is preferred:
+
+    if (a_condition_is_not_valid)
+        return nullptr;
+    if (an_other_condition)
+        return nullptr;
+
+    auto x = std::make_shared<object>();
+
+    x->start();
+    x->save();
+
+    return x;
+
+Additional rules:
+
+  - Do never put parentheses between the returned value,
+  - Do not put a else branch after a return.
+
+### Auto
+
+We encorage usage of `auto`, it reduces code maintainance as you don't need to
+change your code when your rename types.
+
+````cpp
+auto it = std::find_if(v.begin(), v.end(), [&] (const auto& obj) {
+    return obj.key() == "foo";
+});
+
+for (const auto& pair : a_map)
+    std::cout << pair.first << " = " << pair.second << std::endl;
+````
+
+But do not use `auto` to write code like in python, this is not acceptable:
+
+````cpp
+    auto o = my_object("foo");
+````