Currently there is no testing for ClangTypeParser even though it's used in
production. This is because adding integration tests is very hard: they require
testing the build time behaviour at runtime, or else they'd be build failures
intead of test failures. There's a PR available for integration tests but it's
incomplete.
In contrast ClangTypeParser can be sort of unit tested. This follows the
structure of `test/test_drgn_parser.cpp` with some differences. There is a
tonne of boilerplate for setting up the Clang tool, and this set of testing
operates on type names instead of OID functions. The new tests are also
incredibly slow as they compile the entire `integration_test_target.cpp` (which
is huge) for every test case. I don't think this is avoidable without
compromising the separation of the tests somewhat due to the way Clang tooling
forces the code to be structured.
Currently I can't run these tests locally on a Meta devserver due to some
weirdness with the internal build and the `compile_commands.json` file. They
run in the CI and on any other open source machine though so I'm happy to merge
it - it's still useful. I'm going to close the PR to change the devserver build
given I'll be unable to follow up if it ends up being bad.
Test plan:
- CI
This extracts the compatibility logic from AddPadding, which allows for it to be
simplified and will make it easier to extend and eventually remove in the
future. No functional changes.
This lets us remove fields from types when they are no longer needed,
speeding up later passes.
A secondary benefit of pruning unused types means that we sometimes
remove types for which we can't generate correct C++ code. This can
allow us to CodeGen for complex types which reference these broken types
without actually requiring them (e.g. as template parameters).
Add a new feature flag "prune-type-graph" to control this pass. It makes
sense to prune most of the time, but for testing CodeGen functionality
on a wider range of types, it will be useful to have the option to not
prune.
Also reshuffle CodeGen's passes to fix an alignment bug with removed
members.
Change RemoveMembers to actually remove members instead of replacing
them with padding. AddPadding must be run afterwards to fill in the
gaps.
TypeGraphParser parses a textual type graph, as emitted by Printer.
It also doubles as a way of ensuring that Printer displays all
information about a type graph, to aid with debugging.
Convert Flattener unit tests over to this new framework as a first step.
Use fully qualified names to determine if a class is really the child of
our type. It may be that it is the child of another type with an
identical name in another namespace.
