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

[Stefan Monnier <monnier@iro.umontreal.ca>]

> unqualified names in separate entries, "could potentially more than double
> the size of the tag file". Which increases the time it takes to load one,
> and might (if we make more progress on Stefan's suggestion not to pre-build
> tags completion table) also make completion slower, in projects of
> certain size.

FWIW, doubling the size of the TAGS file will also double the size of
the obarray and hence increase the completion time similarly regardless
of whether we keep using an obarray or if we switch to searching the
TAGS buffers.

Yet another alternative is to build a trie, which would speed up
prefix (and partial) completion (but not substring completion).


        Stefan