Previously, the `catch_discover_tests` would prepare the entire CTest
command (e.g. `add_test(...)` or `set_tests_properties(...)`) first, and
then escape it when finished. However, this caused lot of the command args
to be escaped over and over again (e.g. executable name or Catch2's reporter
args), for no reason, as they were always the same, and thus their escaping
was always the same.
Until recently, the performance overhead didn't matter as there were many
spots which had quadratic runtime in number of tests. However, the recent
refactorings fixed these, and this commit now improves the throughput by
10-20%.
Also extended the benchmarked COUNTS in `benchmark_discovery.py`,
because the performance is now good enough that it is reasonable
to benchmark 16k tests.
This was another place where the script triggered the quadratic runtime
from calling `string(APPEND` (or `list(APPEND`) repeatedly. As in
60c8b87, we avoid this by flushing the test list into a file every
50kB of text input.
As the string with the test list never grew quite as much as the
string that contains all the test definitions, this only provides
significant savings for high number of tests. It starts being
properly measurable around 4k tests at ~100ms, but grows to ~4s at
32k tests.
There were 2 separate bugs, one recently added and one ancient
(since roughly the first version of the registration script).
1) The recent refactoring of how the JSON output from Catch2 is
parsed caused shadowing between the variable containing the
per-test JSON fragments and the accumulator of test names for
<target>_TESTS variable. This led to the variable containing
both the names and the JSON fragments, and thus being completely
wrong.
2) The test name accumulation has never accounted for characters
that need escaping to be present in a CMake list. This means
that e.g. test names with semicolon in them would end up with
two elements in the test list.
Both of these are now fixed, at the cost of extra complexity and
my sanity as I had to learn more about CMake escaping rules.
(CMake escaping rules are dumb)
* Quiet verbosity provides just the test names
* Normal verbosity adds tags
* High verbosity add the source location of the tests
Listing tests with the quiet verbosity results in about 1/4 of the
previous output, which leads to measurably faster execution of
`catch_discover_tests` when it does not need tags for labels.
(If it does need tags, the output is about 1/2 of previous).
Using CMake's `string(JSON` to parse JSON array leads to quadratic
running time in number of tests, see https://gitlab.kitware.com/cmake/cmake/-/work_items/27985
This leads to _terrible_ runtime for `catch_discover_tests` when called
on binaries with lot of tests (1k+). To get reasonable runtimes, we have
to avoid using `string(JSON` to parse out the individual test objects
from the array with all tests.
This commit replaces the sane approach of using real JSON parser with
a set of terrible hacks, where we use CMake's string APIs to split the
JSON array on what looks like object boundary (`}<ws>*,<ws>*{`), and then
checking whether the resulting thing can be parsed as JSON object. If not,
we append the next piece and check again. And again, and again, until we
get a proper JSON object.
This is all around a hilariously terrible idea, however:
1) It works in practice for all tested inputs.
2) It improves the time it takes to run `catch_discover_tests` on binary
with 1k tests from 4.2s to 1.1s and 2k tests from 16s to 3.9s.
Repeatedly calling `string(APPEND` on the same destination string
leads to quadratic running time. We avoid this by flushing the CTest
script into a file periodically, currently every 50kB of text.
This can cause _slight_ slowdown just around the flush boundary (each
file write is quite expensive, so if we flush just before the last test
is written, it hurts), but it avoids terrible performance for large
test suites.
The performance is roughly equal at 500 tests to discover, and clearly
wins at more; for 1/2/4/8 k tests, the improvements are 0.3/1.6/6.4/27 s.
The previous approach was for `add_command` to behave as append function
via concatenating the command string internally and then saving it into
`PARENT_SCOPE`. Because this in practice ended up meaning concatenating
a copy of the string inside the function and then overwriting the string
outside the function, the performance was lacking.
The new approach is for `prepare_command` to only escape & return the
command from single call, and the caller is responsible for concatenating
the result. Since the actual concatenation no longer crosses function
scope boundaries, the performance is much better, even though the scaling
is still quadratic.
The new approach only takes 1/4-1/5 of the time, saving ~1s at 1k tests,
4.5s at 2k tests and 19s at 4k tests.
When using catch_discover_tests() with DISCOVERY_MODE PRE_TEST and a
multi-config generator (e.g. Ninja Multi-Config), if a test target has
zero discoverable tests (e.g. all tests tagged with [.]), ctest fails:
CMake Error: include could not find requested file:
.../test-hidden-b12d07c_tests-Release.cmake
The early return added in #2962 (76f70b14) correctly prevented a JSON
parsing crash for zero tests, but skipped writing the ctest file. The
PRE_TEST include script unconditionally includes this file, so the
missing file causes a hard error that aborts all test discovery.
Write an empty file before returning early so the include always
succeeds.
Classes will automatically inherit the virtual-ness of their base
class destructors. If the base class already has a virtual
destructor and the derived class needs default destructor semantics
then the derived class can omit defining the destructor in favor of
the compiler automatically defining it.
This has an additional benefit of reenabling move semantics. The
presence of a user-specified destructor automatically disables move
operations.
Martin Hořeňovský
Phil Nash
Manuel Knörle
Nikolay Baklicharov
Sung, Po Han
Chris Thrasher
Holger Kaelberer
Chien-Yu Lin
Andy Phillips
Cristian Le
Holger KaelbererandHolger Kaelberer
Ilya Arzhannikov