This removes about 200 pointless copies from printing the help
message (the original motivation for the change), and also nicely
improves performance of the various reporters that depend on
TextFlow.
The code is now even worse mess than before, due to the ad-hoc
implementation of Result-ish type based on virtual functions in
Clara, but it has dropped the allocations for empty binary down
to 151.
Because TokenStream is copied around a lot, moving it to use
`StringRef` removes _a lot_ of allocations per `Opt` in the parser.
Args are not copied around much, but changing them as well makes it
obvious that they do not participate in the ownership.
The changes add up to removing ~180 allocations for "empty"
invocation of the test binary.
(`./tests/ExtraTests/NoTests --allow-running-no-tests -o /dev/null`
is down to 317 allocs)
* Clara::Opt::getHelpColumns returns single item
It could never return multiple items, but for some reason it
was wrapping that single item in a vector.
* Use ReusableStringStream in Clara
* Reserve HelpColumns ahead of time
* Use StringRef for descriptions in HelpColumn type
The combination of these changes ends up removing about 7% (~200)
of allocations when Catch2 has to prepare output for `-h`.
There is no good reason for these to be std::strings, as these
are just (optional) constants for nice user output. This ends up
reducing the allocations significantly.
When measuring allocations when running no tests, the changes are
`tests/SelfTest` 9213 -> 7705
`tests/ExtraTests/NoTests` 3723 -> 2215
Most of the changes are completely pointless renaming of constructor
arguments so that they do not use the same name as the type members,
but 🤷Closes#2015
Anchoring the vtables does 2 things
1) Fixes some instances of `-Wweak-vtables`
2) Decreases code size and linker pressure
However, there are still some unanchored ones, and thus we have
to keep suppressing `-Wweak-vtables` warning for Clang.
* Clara is now split between a header and a cpp file.
* Removed the deprecated `+` and `+=` operators for composing
a parser.
* Renamed `clara` and `detail` namespaces to be inline with the
rest of Catch2 (they are now `Clara` and `Detail` respectively).
* Taken most of user-exposed types out of the `Detail` namespace
completely (instead of using `using` directives to bring them into
the outer namespace).
