bug#20629: 25.0.50; Regression: TAGS broken, can't find anything in C++ files.

["Francesco Potortì" <pot@gnu.org>]

Two point that are maybe useful for clarifying something.


Explicit vs implicit tag:

As far as etags.c is concerned, there is no *logical* difference between
an explicit tag and an implicit tag.  Both are tags and should be viewed
and interpreted as such.  The fact that a tag is explicit or implicit is
*only* an optimization, intended to reduce the size of the TAGS file and
the time needed to load it from disk.  There should be *no* difference
between the treatment of implicit and explicit tags when parsing TAGS
file entries.  Given that in the 15+ years since implicit tags where
introduced the trade-offs between disk space and CPU time have changed,
it could maybe make sense to remove the implicit tag concept altogether,
and only have explicit tags, should this make things easier.


Tagged vs non-tagged entries:

An entry is tagged only when necessary, that is, when it would be
ambiguous or difficult to match without a tags.  Again, this is only an
optimization, but this one has logical consequences.  For example, for a
function declaration it can be useful to make it clear what is the
identifier to be matched, so there is a tag.  In class-based programs,
like C++, it can be useful to provide a fully-qualified name for an
identifier, so there is a class::id tag.  Here again, it may make sense
to tag all entries, if it makes TAGS parsing easier or more accurate.