C++ coding style guide
Naming conventions
Class names
Use camel caps for class names:
class FooBar
{
...
};
Function names
Use lower-case for function names and underscore to separate words:
foo();
bar();
foo_bar(...);
Functions returning a value should be given the name of that value, for example:
class Array:
{
public:
/// Return size of array (number of entries)
std::size_t size() const;
};
In the above example, the function should be named size
rather
than get_size
. On the other hand, a function not returning a value
but rather taking a variable (by reference) and assigning a value to
it, should use the get_foo
naming scheme, for example:
class Parameters:
{
public:
/// Retrieve all parameter keys
void get_parameter_keys(std::vector<std::string>& parameter_keys) const;
};
Variable names
Use lower-case for variable names and underscore to separate words:
Foo foo;
Bar bar;
FooBar foo_bar;
Enum variables and constants
Enum variables should be lower-case with underscore to separate words:
enum Type {foo, bar, foo_bar};
We try to avoid using #define
to define constants, but when
necessary constants should be capitalized:
#define FOO 3.14159265358979
File names
Use camel caps for file names if they contain the
declaration/definition of a class. Header files should have the suffix
.h
and implementation files should have the suffix .cpp
:
FooBar.h
FooBar.cpp
Use lower-case for file names that contain utilities/functions (not classes).
Miscellaneous
Indentation
Indentation should be two spaces and it should be spaces. Do not use tab(s).
Integers and reals
Use std::size_t
instead of int
(unless you really want to use
negative integers or memory usage is critical).
std::size_t i = 0;
double x = 0.0;
Placement of brackets and indent style
Use the BSD/Allman style when formatting blocks of code, i.e., curly brackets following multiline control statements should appear on the next line and should not be indented:
for (std::size_t i = 0; i < 10; i++)
{
...
}
For one line statements, omit the brackets:
for (std::size_t i = 0; i < 10; i++)
foo(i);
Header file layout
Header files should follow the below template:
// Copyright (C) 2008 Foo Bar
//
// This file is part of DOLFIN.
//
// DOLFIN is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// DOLFIN is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with DOLFIN. If not, see <http://www.gnu.org/licenses/>.
//
// Modified by Bar Foo 2008
#ifndef __FOO_H
#define __FOO_H
namespace dolfin
{
class Bar; // Forward declarations here
/// Documentation of class
class Foo
{
public:
...
private:
...
};
}
#endif
Implementation file layout
Implementation files should follow the below template:
// Copyright (C) 2008 Foo Bar
//
// This file is part of DOLFIN.
//
// DOLFIN is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// DOLFIN is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with DOLFIN. If not, see <http://www.gnu.org/licenses/>.
//
// Modified by Bar Foo 2008
#include <dolfin/Foo.h>
using namespace dolfin;
//-----------------------------------------------------------------------------
Foo::Foo() : // variable initialization here
{
...
}
//-----------------------------------------------------------------------------
Foo::~Foo()
{
// Do nothing
}
//-----------------------------------------------------------------------------
The horizontal lines above (including the slashes) should be exactly 79 characters wide.
Including header files and using forward declarations
Do not use #include <dolfin.h>
or #include
<dolfin/dolfin_foo.h>
inside the DOLFIN source tree. Only include
the portions of DOLFIN you are actually using.
Include as few header files as possible and use forward declarations
whenever possible (in header files). Put the #include
in the
implementation file. This reduces compilation time and minimizes the
risk of cyclic dependencies.
Explicit constructors
Make all one argument constructors (except copy constructors) explicit:
class Foo
{
explicit Foo(std::size_t i);
};
Virtual functions
Always declare inherited virtual functions as virtual in the subclasses. This makes it easier to spot which functions are virtual.
class Foo
{
virtual void foo();
virtual void bar() = 0;
};
class Bar : public Foo
{
virtual void foo();
virtual void bar();
};
Use of libraries
Prefer C++ strings and streams over old C-style char*
Use std::string
instead of const char*
and use
std::istream
and std::ostream
instead of FILE
. Avoid
printf
, sprintf
and other C functions.
There are some exceptions to this rule where we need to use old
C-style function calls. One such exception is handling of command-line
arguments (char* argv[]
).
Prefer smart pointers over plain pointers
Use std::shared_ptr
and std::unique_ptr
in favour of plain
pointers. Smart pointers reduce the likelihood of memory leaks and
make ownership clear. Use unique_ptr
for a pointer that is not
shared and shared_ptr
when multiple pointers point to the same
object.
Comments
Comment your code, and do it often. Capitalize the first letter and don’t use punctuation (unless the comment runs over several sentences). Here’s a good example from
TopologyComputation.cpp
:Always use
//
for comments and///
for documentation. Never use/* foo */
, not even for comments that runs over multiple lines.