This should decrease the number of allocations before main is entered
significantly, but complicates the code somewhat in return.
Assuming I used `massif` right, doing just `SelfTest --list-tests`
went from 929 allocations at "Remove gcc-4.9 from the travis builds"
(2 commits up), to 614 allocations with this commit.
Now a `TEST_CASE` macro should create a single TestCaseInfo and then
it should never be copied around. This, together with latter changes,
should significantly decrease the number of allocations made before
`main` is even entered.
In the future, we will also want to introduce our own
`uniform_int_distribution` and `uniform_real_distribution` to get
repeatable test runs across different platforms.
This way it is explicit when there is a `StringRef` -> `std::string`
conversion and makes it easier to look for allocations that could
be avoided.
Doing this has already removed one allocation per registered test
case, as there was a completely pointless `StringRef` -> `std::string`
conversion when parsing tags of a test case.
This PR ultimately does 3 things
* Separately tracks matched tests per each filter part (that is, a set of filters separated by an OR (`,`)), which allows Catch2 to report each of the alternative filters that don't match any tests.
* Fixes `-w NoTests` to return non-zero in the process
* Adds tests for `-w NoTests`.
ReusableStringStream holds a std::ostringstream internally, but only exposes the ostream interface.
It caches a pool of ostringstreams in a vector which is currently global, but will be made thread-local.
Altogether this should enable both runtime and compile-time benefits. although more work is needed to realise the compile time opportunities.
