linux内核编程风格.pdf

Linuxkernelcodingstyle

Thisisashortdocumentdescribingthepreferredcodingstylefor
the
linuxkernel.Codingstyleisverypersonal,andIwon't_force_my
viewsonanybody,butthisiswhatgoesforanythingthatIhaveto
be
abletomaintain,andI'dpreferitformostotherthingstoo.
Please
atleastconsiderthepointsmadehere.

Firstoff,I'dsuggestprintingoutacopyoftheGNUcoding
standards,
andNOTreadit.Burnthem,it'sagreatsymbolicgesture.

Anyway,heregoes:

Chapter1:Indentation

Tabsare8characters,andthusindentationsarealso8characters.
Therearehereticmovementsthattrytomakeindentations4(oreven
2!)
charactersdeep,andthatisakintotryingtodefinethevalueofPI
to
be3.

Rationale:Thewholeideabehindindentationistoclearlydefine
where
ablockofcontrolstartsandends.Especiallywhenyou'vebeen
looking
atyourscreenfor20straighthours,you'llfinditaloteasierto
see
howtheindentationworksifyouhavelargeindentations.

Now,somepeoplewillclaimthathaving8-characterindentations
makes
thecodemovetoofartotheright,andmakesithardtoreadona
80-characterterminalscreen.Theanswertothatisthatifyouneed
morethan3levelsofindentation,you'rescrewedanyway,andshould
fix
yourprogram.

Inshort,8-charindentsmakethingseasiertoread,andhavethe
added
benefitofwarningyouwhenyou'renestingyourfunctionstoodeep.
Heedthatwarning.

Thepreferredwaytoeasemultipleindentationlevelsinaswitch
statementis
toalignthe"switch"anditssubordinate"case"labelsinthesame
column
insteadof"double-indenting"the"case"labels.E.g.:

switch(suffix){
case'G':
case'g':
mem<<=30;
break;
case'M':
case'm':
mem<<=20;
break;
case'K':
case'k':
mem<<=10;
/*fallthrough*/
default:
break;
}

Don'tputmultiplestatementsonasinglelineunlessyouhave
somethingtohide:

if(condition)do_this;
do_something_everytime;

Don'tputmultipleassignmentsonasinglelineeither.Kernel
codingstyle
issupersimple.Avoidtrickyexpressions.

Outsideofcomments,documentationandexceptinKconfig,spacesare
never
usedforindentation,andtheaboveexampleisdeliberatelybroken.

Getadecenteditoranddon'tleavewhitespaceattheendoflines.

Chapter2