Coding Guidelines

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InspIRCd Coding Guidelines

The following are a set of guidelines for writing patches to InspIRCd, or for creating modules for distribution with the official package. These guidelines were written a time after InspIRCd development started, and so not all code yet follows these. This will be rectified with time.

Comments

Multi Line

Multiple line comments should follow the C-style comment, for example:

/*
 * This is a multiple line comment, huzzah..
 */

Single Line

Single line comments should also be in the C style, for example:

/* This is a boring one-line comment */

Doxygen commenting

If you wish your comment to show in doxygen, the comment should be directly above the item you are documenting (a class, function, enum, etc) and the first line should be "/**". For example:

/** This is a doxygen multiline comment.
 * Description of thingymebob here.
 */

The first line after the "**" is used as the short description of the item (up to the full stop) and everything afterwards as the detailed description.

Indentation

Tabs. Tabs. ONLY TABS. Use a single tab for each level of indentation, for example:

int main()
{
<tab>if (condition)
<tab>{
<tab><tab>code
<tab>}
}

Separation

Always put a space in between a keyword like if/while and the condition, for example:

if (foo == bar)

NOT

if(foo == bar)

Braces

Always put braces opening and closing blocks on separate lines, see the identation example. For example, place braces like this:

if (apples == "green")
{
        cout << "Apples are green" << endl;
}

and not:

if (apples == "green") {
        cout << "Apples are green" << endl;
}

The one exception to this is if you are declaring a class method which is only one line long, in that case the following is acceptable in most cases:

class foo : public bar
{
        foo() { }
        getrandomfoo() { return rand(); }
};

Templates

Where possible, use templates rather than #defines. Avoid use of RTTI.

Structs

Structs should be declared in the following fashion:

struct BodyPartBasket
{
        int arms;
        int legs;
        int scrotalsacs;
};

and not like this:

typedef struct
{
        int arms;
        int legs;
        int scrotalsacs;
} BodyPartBasket;

The second way is not required in C++ to be able to do this:

BodyPartBasket mybasket;

Plus, placing the name at the bottom of the declaration makes readability more difficult (as you have to scroll down to the bottom of the struct to find its name).

Variable naming

Class and struct names should be in camel case with a leading capital letter, for example "MyBagOfBones" and not "my_bag_of_bones" or "mybagofbones". Variable names can be in either camel case with a leading capital letter or alternatively all lower case, so long as the same naming convention is adhered to throughout the class. No classes or variables should be named in capitals unless this makes sense for the name (for example "class DNS"). Constants and enum values should always be completely in CAPITALS and underscores may be used, for example:

enum DecayState
{
        DECAYED_MOULDY  = 0,
        DECAYED_SMELLY  = 1,
        DECAYED_MAGGOTS = 2
};

All value names in an enum should be started with the same text which should be related in some way to the enum's use. For example "DNS_CNAME, DNS_A, DNS_AAAA".

Use of references

Wherever possible, when dealing with any class larger than the 4 bytes in size, pass a const reference rather than a copy of the class. For example:

MyThingy::MyThingy(const std::string &thingyvalue)
{
}

Of course, if you intended to change the string you can just omit the 'const'.

Use of char pointers

Whenever you use char pointers (char*, char**) try to use const equivalents. This is much safer and avoids ugly and dangerous casts. For example:

MyThingy::Thingify(const char* const* wotsits)
{
}

If it is possible without performance loss, consider avoiding char pointers altogether and using std::string or irc::string instead.

Use of STL

For more information on use of STL in InspIRCd, please see the separate STL FAQ.

Making copies of data

Never ever make a copy of a piece of data unless it is absolutely necessary. For example, don't use strlcpy() to make a copy of the const char* string returned by std::string::c_str(), if the change can be done to the std::string itself. The same goes for unnecessary variable assignments, especially those which assign large classes.

namespace std

Avoid the following:

using namespace std;

It might take a bit more typing, but things work better if you don't set (then later assume) the namespace -- specify it explicitly when you want to use it.

Linefeeds

Unix linefeeds only please. We do not like to see our screens covered in ^M. :-)

Portability

Always make sure your code is portable to all supported operating systems, remember of course that as of 1.1.8 this includes windows. Don't write code that only works on windows, or only works on Linux. Test your code on all platforms or ask for help from other developers who have the platforms you want to test on.

new() and delete(), malloc() and free()

Apart from the fact that using malloc() and free() is bad practice in C++ code, you must never use malloc() or free() in InspIRCd, within its modules or within the core. This is because if you use malloc() or free() in windows, the memory is claimed from the program's local heap. In windows, each shared object (module, dll) has its own heap, which is protected from other dlls and executables. To get around this issue and allow more posix-like memory access from other dlls in the program (other modules), InspIRCd overrides the operators new and delete to ensure that memory allocated by them comes from the windows global heap. If you use malloc() and free() for this, the ircd will segfault when another module tries to access the memory you have allocated!

strdup()

As with malloc(), above, strdup() should be avoided. Where strdup() is absolutely necessary, use strnewdup() which is our strdup() implementation that calls operator new instead of using malloc(). char arrays allocated by strnewdup() should be deleted with operator delete[].

CoreExport and DllImport

Prefix all types you want to import or export to other modules with CoreExport and DllImport macros. These do nothing in POSIX operating systems, however in windows these are expanded to the instructions __declspec(dllimport) and __declspec(dllexport) respectively depending on where they are used and how.

External Dependencies

If a module is compiled as standard, or the code is part of the core, you must not use any dependencies that are not available as standard on all supported operating systems beyond libstdc++, libc, and whatever else is currently required to build the core. Modules which use nonstandard dependencies belong in the modules/extra directory.

Profiling and Performance

It is one thing to assume that code performs bad, it is another thing to prove that it actually is. A lot of experienced programmers talk about 'premature optimisation', and here is what it means: if you have a piece of code called once on startup that takes 10 seconds instead of one second to run, and a piece of code that takes 0.05 seconds to run when it should take 0.01, and it is called once per second, the second piece of code is the priority.

In other words, make sure that what you think is slow, and a performance problem in Insp actually is.

To do this, use the callgrind tool from Valgrind (valgrind --tool=cachegrind bin/inspircd -nofork -debug), and kcachegrind (or similar) to view the output files.