CTAGS(7)

NAME
ctags - Incompatibilities between Universal-ctags and Exuberant-ctags

SYNOPSIS
ctags [options] [file(s)]
etags [options] [file(s)]

DESCRIPTION

This page describes major incompatible changes introduced to Universal-ctags forked from Exuberant-ctags.

INCOMPATIBILITIES IN COMMAND LINE INTERFACE

  The order of application of patterns and extensions in --langmap

When applying mappings for a name of given source file, Exuberant-ctags tests file name patterns AFTER file extensions (e-map-order). Universal-ctags does this differently; it tests file name patterns BEFORE file extensions (u-map-order).

This incompatible change is introduced to deal with the following situation:

•   "build.xml" as a source file,

•   The "Ant" parser declares it handles a file name pattern "build.xml", and

•   The "XML" parser declares it handles a file extension "xml".

    Which parser should be used for parsing "build.xml"? The assumption of Universal-ctags is the user may want to use the "Ant" parser; the file name pattern it declares is more specific than the file extension that the "XML" parser declares. However, e-map-order chooses the "XML" parser.

    So Universal-ctags uses the u-map-order even though it introduces an incompatibility.

    --list-map-extensions=language and --list-map-patterns=language options are helpful to verify and the file extensions and the file name patterns of given language.

  Unexpected synchronization between --file-scope option and F/fileScope extra

Universal-ctags introduces "F/fileScope" extra as the alternative to --file-scope option.

Providing the two way to control the same thing in Universal-ctags internal can cause a trouble.

A user, expecting "--file-scope=yes" is enabled by default, gives "--extras=q". The intention of the user may be just enabling "q/qualified". However, "--extras=q" is evaluated as "disabling all extras including F/fileScope, then enabling only q/qualified". Unexpectedly the command line becomes as if "--file-scope=no" is set.

In this case, the user should set "--extras=+q" instead of "--extras=q".

  Language and kind definitions

  Language name defined with --langdef=name option

The characters you can use are more restricted than Exuberant-ctags. For more details, see the description of --langdef=name in ctags-optlib(7).

  Obsoleting --<LANG>-kinds option

Some options have <LANG> as parameterized parts in their name like --foo-<LANG>=... or --<LANG>-foo=.... The most of all such options in Exuberant-ctags have the former form, --foo-<LANG>=.... The exception is --<LANG>-kinds.

Universal-ctags uses the former form for all <LANG> parameterized option. Use --kinds-<LANG> instead of --<LANG>-kinds in Universal-ctags. --<LANG>-kinds still works but it will be removed in the future.

The former form may be friendly to shell completion engines.

  Disallowing to define a kind with file as name

The kind name "file" is reserved. Using it as part of kind spec in --regex-<LANG> option is now disallowed.

  Disallowing to define a kind with F as letter

The kind letter "F" is reserved. Using it as part of a kind spec in --regex-<LANG> option is now disallowed.

  Disallowing to use other than alphabetical character as kind letter

Exuberant-ctags accepts a character other than alphabetical character as kind letter in --regex-<LANG>=... option. Universal-ctags accepts only an alphabetical character.

  Acceptable characters as parts of a kind name

Exuberant-ctags accepts any character as a part of a kind name defined with --regex-<LANG>=/regex/replacement/kind-spec/.

Universal-ctags accepts only an alphabetical character as the initial letter of a kind name. Universal-ctags accepts only an alphabetical character or numerical character as the rest letters.

An example:

--regex-Foo=/abstract +class +([a-z]+)/\1/a,abstract class/i

Universal-ctags rejects this because the kind name, "abstract class", includes a whitespace character.

This requirement is for making the output of Universal-ctags follow the tags file format.

  A combination of a kind letter and a kind name

In Universal-ctags, the combination of a kind letter and a kind name must be unique in a language.

You cannot define more than one kind reusing a kind letter with different kind names. You cannot define more than one kind reusing a kind name with different kind letters.

An example:

--regex-Foo=/abstract +class +([a-z]+)/\1/a,abstractClass/i
--regex-Foo=/attribute +([a-z]+)/\1/a,attribute/i

Universal-ctags rejects this because the kind letter, "a", used twice for defining a kind "abstractClass" and "attribute".

INCOMPATIBILITIES IN TAGS FILE FORMAT

  Using numerical character in the name part of tag tagfield

The version 2 tags file format, the default output format of Exuberant-ctags, accepts only alphabetical characters in the name part of tag tagfield.

Universal-ctags introduces an exception to this specification; it may use numerical characters in addition to alphabetical characters as the letters other than initial letter of the name part.

The kinds "heading1", "heading2", and "heading3" in the HTML parser are the examples.

OPTION FILES LOADING AT STARTING UP TIME (PRELOAD FILES)

File paths for preload files are changed. Universal-ctags doesn't load "~/.ctags" at starting up time. See "FILES" section of ctags(1).

KIND LETTERS AND NAMES

A kind letter "F" and a kind name "file" are reserved in the main part. A parser cannot have a kind conflicting with these reserved ones. Some incompatible changes are introduced to follow the above rule.

•   Cobol's "file" kind is renamed to "fileDesc" because the kind name "file" is reserved.

•   Ruby's "F" (singletonMethod) is changed to "S".

•   SQL's "F" (field) is changed to "E".

SEE ALSO

ctags(1), ctags-optlib(7), and tags(5).