Lint, or a linter, is a static code analysis tool used to flag programming errors, bugs, stylistic errors and suspicious constructs. The term originates from a

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

utility As a topic of economics, utility is used to model worth or value. Its usage has evolved significantly over time. The term was introduced initially as a measure of pleasure or happiness as part of the theory of utilitarianism by moral philosophe ...

that examined

C language C (''pronounced like the letter c'') is a general-purpose computer programming language. It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential. By design, C's features cleanly reflect the capabilities ...

source code.

History

Stephen C. Johnson, a computer scientist at

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mul ...

, came up with lint in 1978 while debugging the

yacc Yacc (Yet Another Compiler-Compiler) is a computer program for the Unix operating system developed by Stephen C. Johnson. It is a Look Ahead Left-to-Right Rightmost Derivation (LALR) parser generator, generating a LALR parser (the part of a co ...

grammar he was writing for C and dealing with portability issues stemming from porting

to a

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32- bit units. Compared to smaller bit widths, 32-bit computers can perform large calculati ...

machine. The term "lint" was derived from lint, the name for the tiny bits of fiber and fluff shed by clothing, as the command should act like the lint trap in a clothes dryer, detecting small errors to great effect. In 1979, lint was used outside of Bell Labs for the first time, in the seventh version ( V7) of Unix. Over the years, different versions of lint have been developed for many C and

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...

s, and while modern-day compilers have lint-like functions, lint-like tools have also advanced their capabilities. For example, Gimpel's PC-Lint, introduced in 1985 and used to analyze C++ source code, is still for sale.

Overview

The analysis performed by lint-like tools can also be performed by an optimizing compiler, which aims to generate faster code. In his original 1978 paper, Johnson addressed this issue, concluding that "the general notion of having two programs is a good one" because they concentrate on different things, thereby allowing the programmer to "concentrate at one stage of the programming process solely on the

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, ...

s, and correctness of the program, and then later retrofit, with the aid of lint, the desirable properties of universality and portability". Even though modern

s have evolved to include many of lint's historical functions, lint-like tools have also evolved to detect an even wider variety of suspicious constructs. These include "warnings about syntax errors, uses of undeclared variables, calls to deprecated functions, spacing and formatting conventions, misuse of scope, implicit fallthrough in switch statements, missing license headers, nd..dangerous language features". Lint-like tools are especially useful for dynamically typed languages like

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

and Python. Because the compilers of such languages typically do not enforce as many and as strict rules prior to

execution Capital punishment, also known as the death penalty, is the state-sanctioned practice of deliberately killing a person as a punishment for an actual or supposed crime, usually following an authorized, rule-governed process to conclude that ...

, linter tools can also be used as simple debuggers for finding common errors (e.g. syntactic discrepancies) as well as hard-to-find errors such as heisenbugs (drawing attention to suspicious code as "possible errors"). Lint-like tools generally perform static analysis of source code. Lint-like tools have also been developed for other aspects of language, including grammar and style guides.

Specialization

Fortran

Fortran compilers using space-squeezing techniques (e.g.

IBM 1130 The IBM 1130 Computing System, introduced in 1965, was IBM's least expensive computer at that time. A binary 16-bit machine, it was marketed to price-sensitive, computing-intensive technical markets, like education and engineering, succeeding th ...

) made it impossible for the compiler to see the problem with lines like: ::::: .... DO 120 J=1.256 ... 120 CONTINUE which is why programs like ''Lint for Fortran'' can be helpful.

History

Overview

Specialization

Fortran

See also

Notes

References

Further reading