LINT(1) SysV LINT(1)
NAME
lint - a C program checker
SYNOPSIS
lint [ option ] ... file ...
DESCRIPTION
lint attempts to detect features of C program files that are likely to be
bugs, non-portable, or wasteful. It also checks type usage more strictly
than the compilers. Among the things that are currently detected are:
o Unreachable statement
o Loops not entered at the top
o Automatic variables declared and not used
o Logical expressions whose value is constant
o Functions that return values in some places and not in others
o Functions called with varying numbers or types of arguments
o Functions whose values are not used or whose values are used but none
returned.
Arguments whose names 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.
However, if the -p option is used, the portable C lint library (llib-
port.ln) is appended instead. When the -c option is not used, the second
pass of lint checks this list of files for mutual compatibility. When
the -c option is used, the .ln and the llib-lx.ln files are ignored.
Any number of lint options can be used, in any order, intermixed with
file-name arguments.
OPTIONS
Options to Suppress Complaints
-a Suppresses complaints about assignments of long values to
variables that are not long.
-b Suppresses complaints about break statements that cannot be
reached. (Programs produced by lex or yacc often result in
many such complaints).
-h Does not apply heuristic tests that attempt to intuit bugs,
improve style, and reduce waste.
-u Suppresses 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 Suppresses complaints about unused arguments in functions.
-x Does not report variables referred to by external declarations
but never used.
Options That Alter lint's Behavior
-lx Includes additional 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.
-n Does not check compatibility against either the standard or the
portable lint library.
-p Attempts to check portability to other dialects (IBM and GCOS)
of C. 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 Makes stricter checks about pointer and structure alignments
that can prevent portability. Complains about a cast that
converts a pointer from a less restrictive alignment to a more
restrictive alignment. Complains about a structure member that
is not naturally aligned.
-c Causes 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.
-o lib Causes lint to create a lint library with the name llib-
llib.ln. The -c option nullifies any use of the -o option.
The lint library produced is the input 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-llib.ln without
extraneous messages, use the -x option. The -v option is
useful if the source file(s) for the lint library are just
external interfaces (for example, the way the file llib-lc is
written). These option settings are also available through the
use of "lint comments" (see below).
-Amode Specifies the compilation standard to be used by lint. The
mode can be one of the following letters:
xansi Extended ANSI mode. Uses the ANSI C
preprocessor; issues warnings for function calls
not in the scope of a function prototype; allows
Domain extensions; does not define the
preprocessor symbol lint. This mode is the
default.
ansi Strict ANSI mode. Uses the ANSI C preprocessor;
issues warnings for function calls not in the
scope of a function prototype; does not allow
Domain extensions; does not define the
preprocessor symbol lint.
nansi Non-ANSI mode. Uses the K&R C preprocessor;
does not issue warnings for function calls not
in the scope of a function prototype; allows
Domain extensions; defines the preprocessor
symbol lint.
The -D, -U, and -I options of cpp(1) and the -g and -O options of cc(1)
are also recognized as separate arguments. The -g and -O options are
ignored, but, by recognizing these options, lint's behavior is closer to
that of the cc(1) command. Other options are warned about and ignored.
The pre-processor symbols __lint and __LINT__ are defined to allow
certain questionable code to be altered or removed for lint. In
addition, the pre-processor symbol lint is defined when -A nansi is
specified.
Certain conventional comments in the C source change the behavior of
lint:
/*NOTREACHED*/
At appropriate points stops comments about unreachable
code. (This comment is typically placed just after calls
to functions like exit(2)).
/*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.
/*ARGSUSED*/
Turns on the -v option for the next function.
/*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.
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. 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 file name is
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 which 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
prints all the inter-file inconsistencies. This scheme works well with
make(1); it allows make to lint only the source files that have been
modified since the last time the set of source files were linted.
EXTERNAL INFLUENCES
Environment Variables
When set, the TMPDIR environment variable specifies a directory to be
used for temporary files, overriding the default directories /tmp and
/usr/tmp.
Long error messages are split across lines to make them easier to read.
The environment variable COLUMNS controls the maximum number of
characters on each line.
BUGS
exit(2), setjmp(3C), and other functions that do not return are not
understood; this causes various lies.
FILES
/usr/lib/lint[12]
First and second passes
/usr/bin/lint
Shell script that invokes lint[12]
/usr/lib/llib-lc.ln
Declarations for C Library functions (binary format; source is in
/usr/lib/llib-lc)
/usr/lib/llib-port.ln
Declarations for portable functions (binary format; source is in
/usr/lib/llib-port)
/usr/lib/llib-lm.ln
Declarations for Math Library functions (binary format; source is in
/usr/lib/llib-lm)
/usr/tmp/*lint*
Temporaries
SEE ALSO
cc(1), cpp(1), make(1).