Here is how tag syntax is defined for the most popular languages:
enumconstants are also tags, unless you specify ‘--no-defines’ when making the tags table. Similarly, global variables are tags, unless you specify ‘--no-globals’, and so are struct members, unless you specify ‘--no-members’. Use of ‘--no-globals’, ‘--no-defines’ and ‘--no-members’ can make the tags table file much smaller.
You can tag function declarations and external variables in addition
to function definitions by giving the ‘--declarations’ option to
operatordefinitions have tag names like ‘operator+’. If you specify the ‘--class-qualify’ option, tags for variables and functions in classes are named ‘class::variable’ and ‘class::function’. By default, class methods and members are not class-qualified, which allows to identify their names in the sources more accurately.
implementsconstructs. Tags for variables and functions in classes are named ‘class.variable’ and ‘class.function’.
Other commands can make tags as well, if you specify them in the
TEXTAGS before invoking
value of this environment variable should be a colon-separated list of
command names. For example,
TEXTAGS="mycommand:myothercommand" export TEXTAGS
specifies (using Bourne shell syntax) that the commands ‘\mycommand’ and ‘\myothercommand’ also define tags.
defun, any variable defined with
defconst, and in general the first argument of any expression that starts with ‘(def’ in column zero is a tag. As an exception, expressions of the form
(defvar foo)are treated as declarations, and are only tagged if the ‘--declarations’ option is given.
defor with a construct whose name starts with ‘def’. They also include variables set with
set!at top level in the file.
Several other languages are also supported:
In Ada, the same name can be used for different kinds of entity (e.g., for a procedure and for a function). Also, for things like packages, procedures and functions, there is the spec (i.e., the interface) and the body (i.e., the implementation). To make it easier to pick the definition you want, Ada tag names have suffixes indicating the type of entity:
Thus, M-x find-tag RET bidule/b RET will go
directly to the body of the package
bidule, while M-x
find-tag RET bidule RET will just search for any tag
h3headers. Also, tags are
name=in anchors and all occurrences of
localkeywords. Use ‘--globals’ if you want to tag global variables. Tags for subroutines are named ‘package::sub’. The name for subroutines defined in the default package is ‘main::sub’.
classat the beginning of a line generate a tag.
moduleat the beginning of a line generate a tag. Constants also generate tags.
You can also generate tags based on regexp matching (see Etags Regexps) to handle other formats and languages.