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Clean up some docs

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* Consistent line endings in rippled-example.cfg
* Rewrite CodingStyle.md. Get down to top priorities
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Edward Hennis
2014-08-07 16:17:09 -04:00
committed by Vinnie Falco
parent af75b55ef7
commit a86f0a743c
2 changed files with 907 additions and 1038 deletions
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doc/CodingStyle.md
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@@ -2,14 +2,38 @@
# Coding Standards
Coding standards used here are extreme strict and consistent. The style
evolved gradually over the years, incorporating generally acknowledged
best-practice C++ advice, experience, and personal preference.
Coding standards used here gradually evolve and propagate through
code reviews. Some aspects are enforced more strictly than others.
## Don't Repeat Yourself!
## Rules
The [Don't Repeat Yourself][1] principle summarises the essence of what it
means to write good code, in all languages, at all levels.
These rules only apply to our own code. We can't enforce any sort of
style on the external repositories and libraries we include. The best
guideline is to maintain the standards that are used in those libraries.
* Tab inserts 4 spaces. No tab characters.
* Braces are indented in the [Allman style][1].
* Modern C++ principles. No naked ```new``` or ```delete```.
* Line lengths limited to 80 characters. Exceptions limited to data and tables.
## Guidelines
If you want to do something contrary to these guidelines, understand
why you're doing it. Think, use common sense, and consider that this
your changes will probably need to be maintained long after you've
moved on to other projects.
* Use white space and blank lines to guide the eye and keep your intent clear.
* Put private data members at the top of a class, and the 6 public special
members immediately after, in the following order:
* Destructor
* Default constructor
* Copy constructor
* Copy assignment
* Move constructor
* Move assignment
* Don't over-inline by defining large functions within the class
declaration, not even for template classes.
## Formatting
@@ -17,9 +41,6 @@ The goal of source code formatting should always be to make things as easy to
read as possible. White space is used to guide the eye so that details are not
overlooked. Blank lines are used to separate code into "paragraphs."
* No tab characters please.
* Tab stops are set to 4 spaces.
* Braces are indented in the [Allman style][2].
* Always place a space before and after all binary operators,
especially assignments (`operator=`).
* The `!` operator should always be followed by a space.
@@ -62,156 +83,4 @@ overlooked. Blank lines are used to separate code into "paragraphs."
* Always place a space in between the template angle brackets and the type
name. Template code is already hard enough to read!
## Naming conventions
* Member variables and method names are written with camel-case, and never
begin with a capital letter.
* Class names are also written in camel-case, but always begin with a capital
letter.
* For global variables... well, you shouldn't have any, so it doesn't matter.
* Class data members begin with `m_`, static data members begin with `s_`.
Global variables begin with `g_`. This is so the scope of the corresponding
declaration can be easily determined.
* Avoid underscores in your names, especially leading or trailing underscores.
In particular, leading underscores should be avoided, as these are often used
in standard library code, so to use them in your own code looks quite jarring.
* If you really have to write a macro for some reason, then make it all caps,
with underscores to separate the words. And obviously make sure that its name
is unlikely to clash with symbols used in other libraries or 3rd party code.
## Types, const-correctness
* If a method can (and should!) be const, make it const!
* If a method definitely doesn't throw an exception (be careful!), mark it as
`noexcept`
* When returning a temporary object, e.g. a String, the returned object should
be non-const, so that if the class has a C++11 move operator, it can be used.
* If a local variable can be const, then make it const!
* Remember that pointers can be const as well as primitives; For example, if
you have a `char*` whose contents are going to be altered, you may still be
able to make the pointer itself const, e.g. `char* const foobar = getFoobar();`.
* Do not declare all your local variables at the top of a function or method
(i.e. in the old-fashioned C-style). Declare them at the last possible moment,
and give them as small a scope as possible.
* Object parameters should be passed as `const&` wherever possible. Only
pass a parameter as a copy-by-value object if you really need to mutate
a local copy inside the method, and if making a local copy inside the method
would be difficult.
* Use portable `for()` loop variable scoping (i.e. do not have multiple for
loops in the same scope that each re-declare the same variable name, as
this fails on older compilers)
* When you're testing a pointer to see if it's null, never write
`if (myPointer)`. Always avoid that implicit cast-to-bool by writing it more
fully: `if (myPointer != nullptr)`. And likewise, never ever write
`if (! myPointer)`, instead always write `if (myPointer == nullptr)`.
It is more readable that way.
* Avoid C-style casts except when converting between primitive numeric types.
Some people would say "avoid C-style casts altogether", but `static_cast` is
a bit unreadable when you just want to cast an `int` to a `float`. But
whenever a pointer is involved, or a non-primitive object, always use
`static_cast`. And when you're reinterpreting data, always use
`reinterpret_cast`.
* Until C++ gets a universal 64-bit primitive type (part of the C++11
standard), it's best to stick to the `int64` and `uint64` typedefs.
## Object lifetime and ownership
* Absolutely do NOT use `delete`, `deleteAndZero`, etc. There are very very few
situations where you can't use a `ScopedPointer` or some other automatic
lifetime management class.
* Do not use `new` unless there's no alternative. Whenever you type `new`, always
treat it as a failure to find a better solution. If a local variable can be
allocated on the stack rather than the heap, then always do so.
* Do not ever use `new` or `malloc` to allocate a C++ array. Always use a
`HeapBlock` instead.
* And just to make it doubly clear: Never use `malloc` or `calloc`.
* If a parent object needs to create and own some kind of child object, always
use composition as your first choice. If that's not possible (e.g. if the
child needs a pointer to the parent for its constructor), then use a
`ScopedPointer`.
* If possible, pass an object as a reference rather than a pointer. If possible,
make it a `const` reference.
* Obviously avoid static and global values. Sometimes there's no alternative,
but if there is an alternative, then use it, no matter how much effort it
involves.
* If allocating a local POD structure (e.g. an operating-system structure in
native code), and you need to initialise it with zeros, use the `= { 0 };`
syntax as your first choice for doing this. If for some reason that's not
appropriate, use the `zerostruct()` function, or in case that isn't suitable,
use `zeromem()`. Don't use `memset()`.
## Classes
* Declare a class's public section first, and put its constructors and
destructor first. Any protected items come next, and then private ones.
* Use the most restrictive access-specifier possible for each member. Prefer
`private` over `protected`, and `protected` over `public`. Don't expose
things unnecessarily.
* Preferred positioning for any inherited classes is to put them to the right
of the class name, vertically aligned, e.g.:
class Thing : public Foo,
private Bar
{
}
* Put a class's member variables (which should almost always be private, of course),
after all the public and protected method declarations.
* Any private methods can go towards the end of the class, after the member
variables.
* If your class does not have copy-by-value semantics, derive the class from
`Uncopyable`.
* If your class is likely to be leaked, then derive your class from
`LeakChecked<>`.
* Constructors that take a single parameter should be default be marked
`explicit`. Obviously there are cases where you do want implicit conversion,
but always think about it carefully before writing a non-explicit constructor.
* Do not use `NULL`, `null`, or 0 for a null-pointer. And especially never use
'0L', which is particulary burdensome. Use `nullptr` instead - this is the
C++2011 standard, so get used to it. There's a fallback definition for `nullptr`
in Beast, so it's always possible to use it even if your compiler isn't yet
C++2011 compliant.
* All the C++ 'guru' books and articles are full of excellent and detailed advice
on when it's best to use inheritance vs composition. If you're not already
familiar with the received wisdom in these matters, then do some reading!
## Miscellaneous
* `goto` statements should not be used at all, even if the alternative is
more verbose code. The only exception is when implementing an algorithm in
a function as a state machine.
* Don't use macros! OK, obviously there are many situations where they're the
right tool for the job, but treat them as a last resort. Certainly don't ever
use a macro just to hold a constant value or to perform any kind of function
that could have been done as a real inline function. And it goes without saying
that you should give them names which aren't going to clash with other code.
And `#undef` them after you've used them, if possible.
* When using the `++` or `--` operators, never use post-increment if
pre-increment could be used instead. Although it doesn't matter for
primitive types, it's good practice to pre-increment since this can be
much more efficient for more complex objects. In particular, if you're
writing a for loop, always use pre-increment,
e.g. `for (int = 0; i < 10; ++i)`
* Never put an "else" statement after a "return"! This is well-explained in the
LLVM coding standards...and a couple of other very good pieces of advice from
the LLVM standards are in there as well.
* When getting a possibly-null pointer and using it only if it's non-null, limit
the scope of the pointer as much as possible - e.g. Do NOT do this:
Foo* f = getFoo ();
if (f != nullptr)
f->doSomething ();
// other code
f->doSomething (); // oops! f may be null!
..instead, prefer to write it like this, which reduces the scope of the
pointer, making it impossible to write code that accidentally uses a null
pointer:
if (Foo* f = getFoo ())
f->doSomethingElse ();
// f is out-of-scope here, so impossible to use it if it's null
(This also results in smaller, cleaner code)
[1]: http://en.wikipedia.org/wiki/Don%27t_repeat_yourself
[2]: http://en.wikipedia.org/wiki/Indent_style#Allman_style
[1]: http://en.wikipedia.org/wiki/Indent_style#Allman_style