LINT(1)

LINT(1) | General Commands Manual | LINT(1)

# NAME

`lint` —
a C program verifier

# SYNOPSIS

`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`] [`-R` old=new] [`-U` name] [`-X` id[,id ...]] file ...

# DESCRIPTION

`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 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) 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 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 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 name.

Options

`-a`
  Report assignments of long values to variables that are not long.
`-aa`
  Additional to `-a`, report all assignments of integer values to other integer values which cause implicit narrowing conversion.
`-B` path
  Path to use when looking for the lint1 and lint2 binaries. Defaults to /usr/libexec.
`-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 such complaints.
`-C` 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.
`-c`
  Complain about casts which have questionable portability.
`-D` name[=def]
  Define name for cpp(1), as if by a `#define` directive. If no definition is given, name is defined as 1.
`-d` directory
  Use directory instead of /usr/include as the default place to find include files.
`-e`
  Complain about unusual operations on enum-Types and combinations of enum- and integer-Types.
`-F`
  Print pathnames of files. `lint` normally prints the filename without the path.
`-g`
  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, trailing commas in enum declarations, C++ -style “//” comments, 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 (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.
`-I` directory
  Add directory to the list of directories in which to search for include files.
`-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 compatibility between functions.
`-L` directory
  Search for lint libraries in directory and directory/lint before searching the standard place.
`-l` library
  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.
`-o` 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.
`-P`
  Enable more portability warnings: Enum comparisons, sign extension issues when assigning to wider integer types, overflow warnings when assigning to wider types.
`-p`
  Attempt to check portability of code to other dialects of C.
`-R` old=new
  Remap old directory prefixes to new for reproducible builds.
`-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 traditional C and ANSI C. With the `-s` flag, `__STRICT_ANSI__` is a predefined preprocessor macro.
`-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 suppressed. 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 underscores still are).
`-U` name
  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).

Input Grammar

`lint`'s first pass reads standard C source files. `lint` recognizes the following C comments as commands.

`/* ARGSUSED` n `*/`
  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` n [comment] `*/` or `/* NOSTRICT`n [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. The optional numeric argument suppresses the specific numbered message instead of every message. A list of messages and ids can be found in lint(7).
`/* 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)).
`/* PRINTFLIKE` n `*/`
  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 arguments.
`/* PROTOLIB` n `*/`
  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.
`/* SCANFLIKE` n `*/`
  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 arguments.
`/* VARARGS` 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 `-l`library 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 `lint`ed.

# ENVIRONMENT

`LIBDIR`
  The directory where the lint libraries specified by the `-l`library 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 environment variable.
`CC`
  Location of the C compiler program. Defaults to /usr/bin/cc.

# FILES

/usr/libexec/lint[12]
  programs
/usr/libdata/lint/llib-l*.ln
  various prebuilt lint libraries
/tmp/lint*
  temporaries

# SEE ALSO

cc(1), cpp(1), make(1), lint(7)

# AUTHORS

Jochen Pohl

# BUGS

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.

December 24, 2016 | NetBSD 9.3