lint(1) lint(1)
NAME
lint - a C program checker
SYNOPSIS
lint [options] file . . .
DESCRIPTION
lint detects features of C program files which are likely to
be bugs, non-portable, or wasteful. It also checks type usage
more strictly than the compiler. lint issues error and
warning messages. Among the things it detects are unreachable
statements, loops not entered at the top, automatic variables
declared and not used, and logical expressions whose value is
constant. lint checks for functions that return values in
some places and not in others, functions called with varying
numbers or types of arguments, and functions whose values are
not used or whose values are used but not returned.
Arguments that end with .c are taken to be C source files.
Arguments whose names end with .ln are taken to be the result
of an earlier invocation of lint with either the -c or the -o
option used. The .ln files are analogous to .o (object) files
that are produced by the cc(1) command when given a .c file as
input. Files with other suffixes are warned about and
ignored.
lint takes all the .c, .ln, and llib-lx.ln (specified by -lx)
files and processes them in their command line order. By
default, lint appends the standard C lint library (llib-lc.ln)
to the end of the list of files. When the -c option is used,
the .ln and the llib-lx.ln files are ignored. When the -c
option is not used, the second pass of lint checks the .ln and
the llib-lx.ln list of files for mutual compatibility.
The following options are used to suppress certain kinds of
complaints:
-a Suppress complaints about assignments of long values to
variables that are not long.
-b Suppress complaints about break statements that cannot
be reached.
-h Do not apply heuristic tests that attempt to intuit
bugs, improve style, and reduce waste.
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-m Suppress complaints about external symbols that could be
declared static.
-u Suppress complaints about functions and external
variables used and not defined, or defined and not used.
(This option is suitable for running lint on a subset of
files of a larger program).
-v Suppress complaints about unused arguments in functions.
-x Do not report variables referred to by external
declarations but never used.
The following arguments alter lint's behavior:
-Idir Search for included header files in the directory dir
before searching the current directory and/or the
standard place.
-lx Include the lint library llib-lx.ln. For example, you
can include a lint version of the math library llib-
lm.ln by inserting -lm on the command line. This
argument does not suppress the default use of llib-
lc.ln. These lint libraries must be in the assumed
directory. This option can be used to reference local
lint libraries and is useful in the development of
multi-file projects.
-Ldir Search for lint libraries in dir before searching the
standard place.
-n Do not check compatibility against the standard C lint
library.
-p Attempt to check portability to other machines. Along
with stricter checking, this option causes all non-
external names to be truncated to eight characters and
all external names to be truncated to six characters and
one case.
-s Produce one-line diagnostics only. lint occasionally
buffers messages to produce a compound report.
-k Alter the behavior of /*LINTED [message]*/ directives.
Normally, lint will suppress warning messages for the
code following these directives. Instead of suppressing
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the messages, lint prints an additional message
containing the comment inside the directive.
-y Specify that the file being linted will be treated as if
the /*LINTLIBRARY*/ directive had been used. A lint
library is normally created by using the /*LINTLIBRARY*/
directive.
-F Print pathnames of files. lint normally prints the
filename without the path.
-c Cause lint to produce a .ln file for every .c file on
the command line. These .ln files are the product of
lint's first pass only, and are not checked for inter-
function compatibility.
-ox Cause lint to create a lint library with the name llib-
lx.ln. The -c option nullifies any use of the -o
option. The lint library produced is the input that is
given to lint's second pass. The -o option simply
causes this file to be saved in the named lint library.
To produce a llib-lx.ln without extraneous messages, use
of the -x option is suggested. The -v option is useful
if the source file(s) for the lint library are just
external interfaces.
Some of the above settings are also available through
the use of ``lint comments'' (see below).
-V Write to standard error the product name and release.
-Wfile
Write a .ln file to file, for use by cflow(1).
-Rfile
Write a .ln file to file, for use by cxref(1).
lint recognizes many cc(1) command line options, including -D,
-U, -g, -O, -Xt, -Xa, and -Xc, although -g and -O are ignored.
Unrecognized options are warned about and ignored. The
predefined macro lint is defined to allow certain
questionable code to be altered or removed for lint. Thus,
the symbol lint should be thought of as a reserved word for
all code that is planned to be checked by lint.
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Certain conventional comments in the C source will change the
behavior of lint:
/*ARGSUSEDn*/
makes lint check only the first n arguments for usage; a
missing n is taken to be 0 (this option acts like the -v
option for the next function).
/*CONSTCOND*/ or /*CONSTANTCOND*/ or /*CONSTANTCONDITION*/
suppresses complaints about constant operands for the
next expression.
/*EMPTY*/
suppresses complaints about a null statement consequent
on an if statement. This directive should be placed
after the test expression, and before the semicolon.
This directive is supplied to support empty if
statements when a valid else statement follows. It
suppresses messages on an empty else consequent.
/*FALLTHRU*/ or /*FALLTHROUGH*/
suppresses complaints about fall through to a case or
default labeled statement. This directive should be
placed immediately preceding the label.
/*LINTLIBRARY*/
at the beginning of a file shuts off complaints about
unused functions and function arguments in this file.
This is equivalent to using the -v and -x options.
/*LINTED [message]*/
suppresses any intra-file warning except those dealing
with unused variables or functions. This directive
should be placed on the line immediately preceding where
the lint warning occurred. The -k option alters the way
in which lint handles this directive. Instead of
suppressing messages, lint will print an additional
message, if any, contained in the comment. This
directive is useful in conjunction with the -s option
for post-lint filtering.
/*NOTREACHED*/
at appropriate points stops comments about unreachable
code. [This comment is typically placed just after
calls to functions like exit(2)].
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/*PRINTFLIKEn*/
makes lint check the first (n-1) arguments as usual.
The nth argument is interpreted as a printf format
string that is used to check the remaining arguments.
/*PROTOLIBn*/
causes lint to treat function declaration prototypes as
function definitions if n is non-zero. This directive
can only be used in conjunction with the /* LINTLIBRARY
*/ directive. If n is zero, function prototypes will be
treated normally.
/*SCANFLIKEn*/
makes lint check the first (n-1) arguments as usual.
The nth argument is interpreted as a scanf format string
that is used to check the remaining arguments.
/*VARARGSn*/
suppresses the usual checking for variable numbers of
arguments in the following function declaration. The
data types of the first n arguments are checked; a
missing n is taken to be 0. The use of the ellipsis
terminator (. . .) in the definition is suggested in new
or updated code.
lint produces its first output on a per-source-file basis.
Complaints regarding included files are collected and printed
after all source files have been processed, if -s is not
specified. Finally, if the -c option is not used, information
gathered from all input files is collected and checked for
consistency. At this point, if it is not clear whether a
complaint stems from a given source file or from one of its
included files, the source filename will be printed followed
by a question mark.
The behavior of the -c and the -o options allows for
incremental use of lint on a set of C source files.
Generally, one invokes lint once for each source file with the
-c option. Each of these invocations produces a .ln file that
corresponds to the .c file, and prints all messages that are
about just that source file. After all the source files have
been separately run through lint, it is invoked once more
(without the -c option), listing all the .ln files with the
needed -lx options. This will print all the inter-file
inconsistencies. This scheme works well with make; it allows
make to be used to lint only the source files that have been
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modified since the last time the set of source files were
linted.
FILES
LIBDIR the directory where the lint libraries
specified by the -lx option must exist
LIBDIR/lint[12] first and second passes
LIBDIR/llib-lc.ln declarations for C Library functions
(binary format; source is in
LIBDIR/llib-lc)
LIBPATH/llib-lm.ln declarations for Math Library
functions (binary format; source is in
LIBDIR/llib-lm)
TMPDIR/*lint* temporaries
TMPDIR usually /var/tmp but can be redefined
by setting the environment variable
TMPDIR [see tempnam in tmpnam(3S)].
LIBDIR usually /ccs/lib
LIBPATH usually /usr/ccs/lib:/usr/lib
REFERENCES
cc(1), make(1)
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