lint(CP) 6 January 1993 lint(CP) Name lint - a C program checker Syntax lint [ option ] ... file ... Description The lint command attempts to detect features of the 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 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, func- tions called with varying numbers or types of arguments, and functions whose values are not used or whose values are used but none returned. lint is based on the Microsoft compiler cc. It is capable of understand- ing both ANSI and Microsoft syntax. To check programs written for the AT&T compiler rcc, use the rlint command (see the rlint(CP) manual page). Arguments whose names end with .c are taken to be C source files. Argu- ments 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(CP) 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. 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 compa- tibility. 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, intermixed 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 com- plaints.) -u Suppress 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 Suppress complaints about unused arguments in functions. -x Do not report variables referred to by external declarations but never used. The following arguments alter lint's behavior: -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. -lx Include 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 Do not check compatibility against either the standard or the port- able lint library. -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 pro- duced 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 llib-lc is written). These option settings are also available through the use of ``lint comments'' (see below). -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. The -D, -U, and -I options of cpp(CP) and the -g and -O options of cc(CP) 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(CP) command. Other options are warned about and ignored. The symbols ``__lint'' and ``lint'' should be thought of as reserved words for all code that you plan to check with lint. The default prepro- cessor symbol ``__lint'' is defined to allow certain questionable code to be altered or removed for lint. The preprocessor symbol ``lint'' is also currently defined to allow backward compatibility. Certain conventional comments in the C source will change the behavior of lint: /*ARGSUSED*/ Turns on the -v option for the next function. /*LINTLIBRARY*/ Placed at the beginning of a file turns off complaints about unused functions and function arguments in this file. This is equivalent to using the -v and -x options. /*NOTREACHED*/ Placed at appropriate points stops comments about unreachable code. (This comment is typically placed just after calls to functions like exit(S).) /*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. The lint command 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 will be 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 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(CP); it allows make to be used to lint only the source files that have been modi- fied since the last time the set of source files were linted. 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 for- mat; 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 functions (binary format; source is in LLIBDIR/llib-lm). TMPDIR/*lint* Temporary files. TMPDIR Usually /usr/tmp but can be redefined by setting the environment variable TMPDIR (see tempnam() in tmpnam(S)). Notes exit(S), setjmp(S), and other functions that do not return are not under- stood; this causes various incorrect warnings. See also cc(CP), cpp(CP), make(CP) Standards conformance lint is conformant with: AT&T SVID Issue 2; and X/Open Portability Guide, Issue 3, 1989.