LINT(1) INTERACTIVE UNIX System LINT(1)
NAME
lint - a C program checker
SYNOPSIS
lint [ option ] ... file ...
DESCRIPTION
The lint command attempts to detect features of the C pro-
gram 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
unreachable statements, loops not entered at the top,
automatic variables declared and not used, and logical
expressions whose value is constant. Moreover, the usage of
functions is checked to find 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 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.
The lint command will take all the .c, .ln, and llib-lx.ln
(specified by -lx) files and process 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. How-
ever, 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 may be used, in any order, inter-
mixed with file-name arguments. 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. (Programs produced by lex or yacc will
often result in many such complaints.)
-h Do not apply heuristic tests that attempt to intuit
bugs, improve style, and reduce waste.
-u Suppress complaints about functions and external vari-
ables used and not defined, or defined and not used.
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LINT(1) INTERACTIVE UNIX System LINT(1)
(This option is suitable for running lint on a subset
of files of a larger program.)
-v Suppress complaints about unused arguments in func-
tions.
-x Do not report variables referred to by external
declarations but never used.
The following arguments alter lint's behavior:
-lx Include additional lint library llib-lx.ln. For exam-
ple, 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 mul-
tifile projects.
-n Do not check compatibility against either the standard
or the portable lint library.
-p Attempt 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.
-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.
-o lib
Cause 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 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-llib.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 (for example, the way the file
llib-lc is written). These option settings are also
available through the use of ``lint comments'' (see
below).
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) com-
mand. Other options are warned about and ignored. The
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LINT(1) INTERACTIVE UNIX System LINT(1)
preprocessor symbol ``lint'' is defined to allow certain
questionable code to be altered or removed for lint. There-
fore, the symbol ``lint'' should be thought of as a reserved
word for all code that is planned to be checked by lint.
Certain conventional comments in the C source will 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 declara-
tion. 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.
The lint command produces its first output on a per-source-
file basis. Complaints regarding included files are col-
lected and printed after all source files have been pro-
cessed. 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 will be printed fol-
lowed by a question mark.
The behavior of the -c and the -o options allows for incre-
mental 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 for
each .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 interfile
inconsistencies. This scheme works well with make(1); it
allows make to be used to lint only the source files that
have been modified since the last time the set of source
files were linted.
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LINT(1) INTERACTIVE UNIX System LINT(1)
FILES
LLIBDIR the directory where the lint libraries
specified by the -lx option must
exist, usually /usr/lib
LLIBDIR/lint[12] first and second passes
LLIBDIR/llib-lc.ln declarations for C Library functions
(binary format; source is in
LLIBDIR/llib-lc)
LLIBDIR/llib-port.ln declarations for portable functions
(binary format; source is in
LLIBDIR/llib-port)
LLIBDIR/llib-lm.ln declarations for Math Library func-
tions (binary format; source is in
LLIBDIR/llib-lm)
TMPDIR/*lint* temporaries
TMPDIR usually /usr/tmp but can be redefined
by setting the environment variable
TMPDIR [see tempnam() in tmpnam(3S)].
SEE ALSO
cc(1), cpp(1), make(1).
BUGS
exit(2), setjmp(3C), and other functions that do not return
are not understood; this causes various lies.
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