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.Dd May 26, 2021
.Dt CSTYLE 1
.Os
.
.Sh NAME
.Nm cstyle
.Nd check for some common stylistic errors in C source files
.Sh SYNOPSIS
.Nm
.Op Fl chpvCP
.Oo Ar file Oc Ns …
.Sh DESCRIPTION
.Nm
inspects C source files (*.c and *.h) for common stylistic errors.
It attempts to check for the cstyle documented in
.Lk http://www.cis.upenn.edu/~lee/06cse480/data/cstyle.ms.pdf .
Note that there is much in that document that
.Em cannot
be checked for; just because your code is
.Nm Ns -clean
does not mean that you've followed Sun's C style.
.Em Caveat emptor .
.
.Sh OPTIONS
.Bl -tag -width "-c"
.It Fl c
Check continuation line indentation inside of functions.
Sun's C style
states that all statements must be indented to an appropriate tab stop,
and any continuation lines after them must be indented
.Em exactly
four spaces from the start line.
This option enables a series of checks designed to find
continuation line problems within functions only.
The checks have some limitations; see
.Sy CONTINUATION CHECKING ,
below.
.It Fl p
Performs some of the more picky checks.
Includes ANSI
.Sy #else
and
.Sy #endif
rules, and tries to detect spaces after casts.
Used as part of the putback checks.
.It Fl v
Verbose output; includes the text of the line of error, and, for
.Fl c ,
the first statement in the current continuation block.
.It Fl P
Check for use of non-POSIX types.
Historically, types like
.Sy u_int
and
.Sy u_long
were used, but they are now deprecated in favor of the POSIX
types
.Sy uint_t ,
.Sy ulong_t ,
etc.
This detects any use of the deprecated types.
Used as part of the putback checks.
.It Fl g
Also print GitHub-Actions-style
.Li ::error
output.
.El
.
.Sh ENVIRONMENT
.Bl -tag -compact -width ".Ev CI"
.It Ev CI
If set and nonempty, equivalent to
.Fl g .
.El
.
.Sh CONTINUATION CHECKING
The continuation checker is a reasonably simple state machine that knows
something about how C is laid out, and can match parenthesis, etc. over
multiple lines.
It does have some limitations:
.Bl -enum
.It
Preprocessor macros which cause unmatched parenthesis will confuse the
checker for that line.
To fix this, you'll need to make sure that each branch of the
.Sy #if
statement has balanced parenthesis.
.It
Some
.Xr cpp 1
macros do not require
.Sy ;\& Ns s after them.
Any such macros
.Em must
be ALL_CAPS; any lower case letters will cause bad output.
.Pp
The bad output will generally be corrected after the next
.Sy ;\& , { , No or Sy } .
.El
Some continuation error messages deserve some additional explanation:
.Bl -tag -width Ds
.It Sy multiple statements continued over multiple lines
A multi-line statement which is not broken at statement boundaries.
For example:
.Bd -literal -compact -offset Ds
if (this_is_a_long_variable == another_variable) a =
    b + c;
.Ed
.Pp
Will trigger this error.
Instead, do:
.Bd -literal -compact -offset Ds
if (this_is_a_long_variable == another_variable)
    a = b + c;
.Ed
.It Sy empty if/for/while body not on its own line
For visibility, empty bodies for if, for, and while statements should be
on their own line.
For example:
.Bd -literal -compact -offset Ds
while (do_something(&x) == 0);
.Ed
.Pp
Will trigger this error.
Instead, do:
.Bd -literal -compact -offset Ds
while (do_something(&x) == 0)
    ;
.Ed
.El