Differential D25312 Diff 74521 head/share/man/man9/style.9

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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT		.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY		.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF		.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.		.\" SUCH DAMAGE.
.\"		.\"
.\" From: @(#)style 1.14 (Berkeley) 4/28/95		.\" From: @(#)style 1.14 (Berkeley) 4/28/95
.\" $FreeBSD$		.\" $FreeBSD$
.\"		.\"
.Dd June 30, 2020		.Dd July 16, 2020
.Dt STYLE 9		.Dt STYLE 9
.Os		.Os
.Sh NAME		.Sh NAME
.Nm style		.Nm style
.Nd "kernel source file style guide"		.Nd "kernel source file style guide"
.Sh DESCRIPTION		.Sh DESCRIPTION
This file specifies the preferred style for kernel source files in the		This file specifies the preferred style for kernel source files in the
.Fx		.Fx
▲ Show 20 Lines • Show All 550 Lines • ▼ Show 20 Lines	.Bd -literal
}		}
if (val != NULL)		if (val != NULL)
val = realloc(val, newsize);		val = realloc(val, newsize);
.Ed		.Ed
.Pp		.Pp
Parts of a		Parts of a
.Ic for		.Ic for
loop may be left empty.		loop may be left empty.
Do not put declarations
inside blocks unless the routine is unusually complicated.
.Bd -literal		.Bd -literal
for (; cnt < 15; cnt++) {		for (; cnt < 15; cnt++) {
stmt1;		stmt1;
stmt2;		stmt2;
}		}
.Ed		.Ed
.Pp		.Pp
		A
		.Ic for
		loop may declare and initialize its counting variable.
		.Bd -literal
		for (int i = 0; i < 15; i++) {
		stmt1;
		}
		.Ed
		.Pp
Indentation is an 8 character tab.		Indentation is an 8 character tab.
Second level indents are four spaces.		Second level indents are four spaces.
If you have to wrap a long statement, put the operator at the end of the		If you have to wrap a long statement, put the operator at the end of the
line.		line.
.Bd -literal		.Bd -literal
while (cnt < 20 && this_variable_name_is_too_long &&		while (cnt < 20 && this_variable_name_is_too_long &&
ep != NULL)		ep != NULL)
z = a + really + long + statement + that + needs +		z = a + really + long + statement + that + needs +
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.Ed		.Ed
.Pp		.Pp
The function type should be on a line by itself		The function type should be on a line by itself
preceding the function.		preceding the function.
The opening brace of the function body should be		The opening brace of the function body should be
on a line by itself.		on a line by itself.
.Bd -literal		.Bd -literal
static char *		static char *
function(int a1, int a2, float fl, int a4)		function(int a1, int a2, float fl, int a4, struct bar *bar)
{		{
.Ed		.Ed
.Pp		.Pp
When declaring variables in functions declare them sorted by size,		When declaring variables in functions declare them sorted by size,
then in alphabetical order; multiple ones per line are okay.		then in alphabetical order; multiple ones per line are okay.
If a line overflows reuse the type keyword.		If a line overflows reuse the type keyword.
.Pp		Variables may be initialized where declared especially when they
Be careful to not obfuscate the code by initializing variables in		are constant for the rest of the scope.
the declarations.		Declarations may be placed before executable lines at the start
Use this feature only thoughtfully.		of any block.
DO NOT use function calls in initializers.		Calls to complicated functions should be avoided when initializing variables.
.Bd -literal		.Bd -literal
struct foo one, *two;		struct foo one, *two;
double three;		struct baz *three = bar_get_baz(bar);
int *four, five;		double four;
char *six, seven, eight, nine, ten, eleven, twelve;		int *five, six;
		char *seven, eight, nine, ten, eleven, twelve;

four = myfunction();		four = my_complicated_function(a1, f1, a4);
.Ed		.Ed
.Pp		.Pp
Do not declare functions inside other functions; ANSI C says that		Do not declare functions inside other functions; ANSI C says that
such declarations have file scope regardless of the nesting of the		such declarations have file scope regardless of the nesting of the
declaration.		declaration.
Hiding file declarations in what appears to be a local		Hiding file declarations in what appears to be a local
scope is undesirable and will elicit complaints from a good compiler.		scope is undesirable and will elicit complaints from a good compiler.
.Pp		.Pp
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