LINT(1) BSD General Commands Manual LINT(1)
lint -- a C program verifier
lint [-abceFgHhPprVvwxz] [-i | -nu] [-S | -s | -t] [-B directory] [-D name[=def]]
[-d directory] [-I directory] [-L directory] [-MD] [-l library] [-o outputfile]
[-U name] [-X id[,id ...]] file ...
lint [-abceFgHhprVvwz] [-S | -s | -t] -C library [-B directory] [-D name[=def]]
[-d directory] [-I directory] [-MD] [-U name] [-X id[,id ...]] file ...
lint attempts to detect features of the named C program files that are likely to be bugs, to
be non-portable, or to be wasteful. It also performs stricter type checking than does the C
compiler. The list of errors lint produces are enumerated in lint(7).
lint runs the C preprocessor as its first phase, with the following preprocessor symbols
defined to allow certain questionable code to be altered or skipped: __LINT__, lint, __lint,
__lint__. These symbols should therefore be thought of as reserved words for all code that
is to be checked by lint.
Among the possible problems that are currently noted are unreachable statements, loops not
entered at the top, variables declared and not used, and logical expressions with constant
values. Function calls are checked for inconsistencies, such as calls to functions that
return values in some places and not in others, functions called with varying numbers of
arguments, function calls that pass arguments of a type other than the type the function
expects to receive, functions whose values are not used, and calls to functions not return-
ing values that use the non-existent return value of the function.
Filename arguments ending with .c are taken to be C source files. Filename arguments with
names ending with .ln are taken to be the result of an earlier invocation of lint, with
either the -i, -o or -C option in effect. The .ln files are analogous to the .o (object)
files produced by cc(1) from .c files. lint also accepts special libraries specified with
the -l option, which contain definitions of library routines and variables.
lint takes all the .c, .ln, and llib-llibrary.ln (lint library) files and processes them in
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 -i option is used, the .ln files are ignored. Also,
when the -o or -i options are used, the llib-llibrary.ln files are ignored. When the -i
option is omitted the second pass of lint checks this list of files for mutual compatibil-
ity. At this point, if a complaint stems not from a given source file, but from one of its
included files, the source filename will be printed followed by a question mark.
The special input file name ``-'' causes lint to take input from standard input (until end
of file) and process it as if it were a .c file. If the -i flag is given and ``-'' is named
as one of the input files, the -o flag must also be specified to provide an output file
-a Report assignments of long values to variables that are not long.
-aa Additional to -a, report all assignments of integer values to other inte-
ger values which cause implicit narrowing conversion.
-Bpath Path to use when looking for the lint1 and lint2 binaries. Defaults to
-b Report break statements that cannot be reached. This is not the default
because, unfortunately, most lex(1) and many yacc(1) outputs produce many
-Clibrary Create a lint library with the name llib-llibrary.ln. This library is
built from all .c and .ln input files. After all global definitions of
functions and variables in these files are written to the newly created
library, lint checks all input files, including libraries specified with
the -l option, for mutual compatibility.
-c Complain about casts which have questionable portability.
-Dname[=def] Define name for cpp(1), as if by a #define directive. If no definition is
given, name is defined as 1.
-ddirectory Use directory instead of /usr/include as the default place to find include
-e Complain about unusual operations on enum-Types and combinations of enum-
-F Print pathnames of files. lint normally prints the filename without the
-g Don't print warnings for some extensions of gcc(1) to the C language.
Currently these are nonconstant initializers in automatic aggregate ini-
tializations, arithmetic on pointer to void, trailing commas in enum dec-
larations, C++ -style ``//'' comments, zero sized structures, subscripting
of non-lvalue arrays, prototypes overriding old style function declara-
tions and long long integer types. The -g flag also turns on the keywords
asm and inline (alternative keywords with leading underscores for both asm
and inline are always available).
-H If a complaint stems from an included file lint prints the name of the
included file instead of the source file name followed by a question mark.
-h Apply a number of heuristic tests to attempt to intuit bugs, improve
style, and reduce waste.
-Idirectory Add directory to the list of directories in which to search for include
-i 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 compat-
ibility between functions.
-Ldirectory Search for lint libraries in directory and directory/lint before searching
the standard place.
-llibrary Include the lint library llib-llibrary.ln.
-MD Pass -MD to cpp(1) causing cpp to create files containing dependency
information for each source file.
-n Do not check compatibility against the standard library.
-ooutputfile Name the output file outputfile. The output file produced is the input
that is given to lint's second pass. The -o option simply saves this file
in the named output file. If the -i option is also used the files are not
checked for compatibility. To produce a llib-llibrary.ln without extrane-
ous messages, use of the -u option is suggested. The -v option is useful
if the source file(s) for the lint library are just external interfaces.
-P Enable more portability warnings: Enum comparisons, sign extension issues
when assigning to wider integer types, overflow warnings when assigning to
-p Attempt to check portability of code to other dialects of C.
-r In case of redeclarations report the position of the previous declaration.
-S C9X mode. Currently not fully implemented.
-s Strict ANSI C mode. Issue warnings and errors required by ANSI C. Also
do not produce warnings for constructs which behave differently in tradi-
tional C and ANSI C. With the -s flag, __STRICT_ANSI__ is a predefined
-t Traditional C mode. __STDC__ is not predefined in this mode. Warnings
are printed for constructs not allowed in traditional C. Warnings for
constructs which behave differently in traditional C and ANSI C are sup-
pressed. Preprocessor macros describing the machine type (e.g. sun3) and
machine architecture (e.g. m68k) are defined without leading and trailing
underscores. The keywords const, volatile and signed are not available in
traditional C mode (although the alternative keywords with leading under-
scores still are).
-Uname Remove any initial definition of name for the preprocessor.
-u Do not complain about functions and external variables used and not
defined, or defined and not used (this is suitable for running lint on a
subset of files comprising part of a larger program).
-V Print the command lines constructed by the controller program to run the C
preprocessor and lint's first and second pass.
-v Suppress complaints about unused arguments in functions.
-w Treat warnings as errors.
-X id[,id ...] Suppress error messages identified by the list of ids. A list of messages
and ids can be found in lint(7).
-x Report variables referred to by extern declarations, but never used.
-z Do not complain about structures that are never defined (for example,
using a structure pointer without knowing its contents).
lint's first pass reads standard C source files. lint recognizes the following C comments
/* 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).
/* BITFIELDTYPE */
Suppress error messages about illegal bitfield types if the type is an integer
type, and suppress non-portable bitfield type warnings.
/* CONSTCOND */ or /* CONSTANTCOND */ or /* CONSTANTCONDITION */
Suppress complaints about constant operands for the next expression.
/* FALLTHRU */ or /* FALLTHROUGH */
Suppress 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, mark all functions and variables defined in this
file as used. Also shut off complaints about unused function arguments.
/* LINTED [comment] */ or /* NOSTRICT [comment] */
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.
/* LONGLONG */
Suppress complaints about use of long long integer types.
/* NOTREACHED */
At appropriate points, inhibit complaints about unreachable code. (This comment
is typically placed just after calls to functions like exit(3)).
/* PRINTFLIKEn */
Makes lint check the first (n-1) arguments as usual. The n-th argument is
interpreted as a printf format string that is used to check the remaining argu-
/* 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
/* SCANFLIKEn */
Makes lint check the first (n-1) arguments as usual. The n-th argument is
interpreted as a scanf format string that is used to check the remaining argu-
/* VARARGSn */
Suppress 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 behavior of the -i 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 -i 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 -i option), listing all
the .ln files with the needed -llibrary options. This will print all the inter-file incon-
sistencies. This scheme works well with make(1); it allows make(1) to be used to lint only
the source files that have been modified since the last time the set of source files were
LIBDIR The directory where the lint libraries specified by the -llibrary option must
exist. If this environment variable is undefined, then the default path
/usr/libdata/lint will be used to search for the libraries.
TMPDIR Usually the path for temporary files can be redefined by setting this environ-
CC Location of the C compiler program. Defaults to /usr/bin/cc.
/usr/libdata/lint/llib-l*.ln various prebuilt lint libraries
cc(1), cpp(1), make(1), lint(7)
The routines exit(3), longjmp(3) and other functions that do not return are not understood;
this causes various incorrect diagnostics.
Static functions which are used only before their first extern declaration are reported as
Libraries created by the -o option will, when used in later lint runs, cause certain errors
that were reported when the libraries were created to be reported again, and cause line num-
bers and file names from the original source used to create those libraries to be reported
in error messages. For these reasons, it is recommended to use the -C option to create lint
BSD August 2, 2008 BSD