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LINT(1) General Commands Manual LINT(1)

lint — a C program verifier

lint [-ceFfgHhprsVvxz] [-i | -nu] [-Dname[=def]] [-Idirectory] [-Ldirectory] [-llibrary] [-MD] [-ooutputfile] [-Uname] file ...

lint [-ceFfgHhprsVvz] -Clibrary [-Dname[=def]] [-Idirectory] [-MD] [-Uname] file ...

lint attempts to detect features of the named C program files that are likely to be bugs, non-portable, or wasteful. It also performs stricter type checking than the C compiler. lint runs the C preprocessor as its first phase, with the preprocessor symbol defined to allow certain questionable code to be altered or skipped by lint. Therefore, this symbol should be thought of as a reserved word 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 returning 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), if it exists, 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 the second pass of lint checks this list of files for mutual compatibility. 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 options are as follows:

library
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.
Complain about casts which have questionable portability.
name[=def]
Define name for cpp(1), as if by a #define directive. If no definition is given, name is defined as 1.
Complain about unusual operations on enum-Types and combinations of enum- and -Types.
Print pathnames of files. lint normally prints the filename without the path.
For each warning or error, print the offending line of the corresponding source code file.
Don't print warnings for some extensions of gcc(1) to the C language. Currently these are nonconstant initializers in automatic aggregate initializations, arithmetic on pointer to void, zero sized structures, subscripting of non-lvalue arrays, prototypes overriding old style function declarations and long long integer types. The -g flag also turns on the keywords asm and inline (alternate keywords with leading underscores for both asm and inline are always available).
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.
Apply a number of heuristic tests to attempt to intuit bugs, improve style, and reduce waste.
directory
Add directory to the list of directories in which to search for include files.
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 compatibility between functions.
directory
Search for lint libraries in directory and directory/lint before searching the standard place.
library
Include the lint library llib-llibrary.ln.
Ignored, so the same flags can be passed to lint and cpp(1).
Do not check compatibility against the standard library.
outputfile
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 extraneous 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.
Attempt to check portability of code to other dialects of C.
In case of redeclarations report the position of the previous declaration.
Strict ANSI C mode. Issue warnings and errors required by ANSI C. Also do not produce warnings for constructs which behave differently in traditional C and ANSI C. With the -s flag, __STRICT_ANSI__ is a predefined preprocessor macro.
name
Remove any initial definition of name for the preprocessor.
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).
Print the command lines constructed by the controller program to run the C preprocessor and lint's first and second pass.
Suppress complaints about unused arguments in functions.
Report variables referred to by declarations, but never used.
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 as commands.

n */
Make 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).
or /* CONSTANTCOND */ or /* CONSTANTCONDITION */
Suppress complaints about constant operands for the next expression.
or /* FALLTHROUGH */
Suppress complaints about fall through to a or labelled statement. This directive should be placed immediately preceding the label.
At the beginning of a file, mark all functions and variables defined in this file as . Also shut off complaints about unused function arguments.
[comment] */ or /* NOSTRICT [comment] */
Suppress 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.
Suppress complaints about use of long long integer types.
Tell lint that the function will never return, which means any code following a call to this function is unreachable. This directive should be placed immediately preceding the function.
At appropriate points, inhibit complaints about unreachable code. This comment is typically placed just after calls to functions like exit(3).
n */
Make lint check the first (n-1) arguments as usual. The n-th argument is interpreted as a format string that is used to check the remaining arguments.
n */
Cause 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.
n */
Make lint check the first (n-1) arguments as usual. The n-th argument is interpreted as a format string that is used to check the remaining arguments.
n */
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 inconsistencies. 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 linted.

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.
usually the path for temporary files can be redefined by setting this environment variable.

/usr/libexec/lint[12]
programs
/usr/libdata/lint/llib-lposix.ln
prebuilt POSIX C lint library
/usr/libdata/lint/llib-lstdc.ln
prebuilt ANSI/ISO C lint library
/tmp/lint*
temporaries

cc(1), cpp(1), make(1)

Jochen Pohl

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 unused.

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 numbers 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 libraries.

June 9, 2011 OpenBSD-5.1