CDECL

Section: User Commands (1)
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NAME

cdecl - Compose C declarations

SYNOPSIS

cdecl

DESCRIPTION

Cdecl is a program for encoding and decoding C type-declarations. It reads standard input for statements in the language described below. The results are written on standard output.

Cdecl's scope is intentionally small. It doesn't help you figure out storage classes or initializations.

COMMAND LANGUAGE

There are four statements in the language. The "declare" statement composes a C type-declaration from a verbose description. The "cast" statement composes a C type-cast as might appear in an expression. The "explain" statement decodes a C type-declaration, producing a verbose description. The "help" statement describes the others.

The following grammar describes the language. In the grammar, words in "<>" are non-terminals, bare lower-case words are terminals that stand for themselves. Bare upper-case words are other lexical tokens: NOTHING means the empty string; NAME means a C identifier; NUMBER means a string of decimal digits; and NL means the new-line character.

<program>    ::= NOTHING
               | <program> <stat> NL
<stat>       ::= NOTHING
               | declare NAME as <decl>
               | cast NAME into <decl>
               | explain <cdecl>
               | help
<decl>       ::= array of <decl>
               | array NUMBER of <decl>
               | function returning <decl>
               | function ( NAME ) returning <decl>
               | pointer to <decl>
               | <type>
<cdecl>      ::= <cdecl1>
               | * <cdecl>
<cdecl1>     ::= <cdecl1> ( )
               | <cdecl1> [ ]
               | <cdecl1> [ NUMBER ]
               | ( <cdecl> )
               | NAME
<type>       ::= <typename> | <modlist>
               | <modlist> <typename>
               | struct NAME | union NAME | enum NAME
<typename>   ::= int | char | double | float
<modlist>    ::= <modifier> | <modlist> <modifier>
<modifier>   ::= short | long | unsigned

EXAMPLES

To declare an array of pointers to functions like malloc(3), do declare fptab as array of pointer to function returning pointer to char The result of this command is char *(*fptab[])() When you see this declaration in someone else's code, you can make sense out of it by doing explain char *(*fptab[])() The proper declaration for signal(2) cannot be described in cdecl's language (it can't be described in C either). An adequate declaration for most purposes is given by declare signal as function returning pointer to function returning int The function declaration that results has two sets of empty parentheses. The author of such a function might wonder where the parameters go. declare signal as function (args) returning pointer to function returning int provides the solution: int (*signal(args))()

DIAGNOSTICS

The declare statement tries to point out constructions that are not supported in C. Also, certain non-portable constructs are flagged.

Syntax errors cause the parser to play dead until a newline is read.

BUGS

The pseudo-English syntax is excessively verbose.

This document was created by man2html, using the manual pages.
Time: 00:30:51 GMT, January 03, 2023