* [C++17] Add compile-time reflection for fields.
Included in this commit is the following:
- The C++ generator has been modified so that,
when in C++17 mode, it will emit Table and
Struct field traits that can be used at com-
pile time as a form of static reflection. This
includes field types, field names, and a tuple
of field getter results.
- Diffs to the cpp17 generated files. No other
generated files are affected.
- A unit test that also serves as an example. It
demonstrates how to use the full power of this
reflection to implement a full recursive
JSON-like stringifier for Flatbuffers types,
but without needing any runtime access to the
*.fbs definition files; the computation is
done using only static reflection.
Tested on Linux with gcc 10.2.0.
Fixes#6285.
* Fix int-conversion warning on MSVC.
* Try to fix std::to_string ambiguity on MSVC.
* Fix clang-format diffs.
* Fix more clang-format diffs.
* Fix last clang-format diff.
* Enable C++17 build/test for VC 19 platform in CI.
* Forgot to add value to cmake command line variable.
* Various fixes/changes in response to @vglavnyy's feedback.
* Replace "fields pack" with index-based getters.
* Fix MSVC error.
* Fix clang-format diffs.
* getter_for method returns result instead of address-of-getter.
* Next round of reviewer suggestions.
* Use type instead of hardcoded struct name.
* Fix clang-format diff.
* Add test for FieldType since it is not used in the stringify test.
* Add fields_number field to Traits struct.
* Add --cpp-static-reflection flag and put those features behind it.
* Fix clang-format diffs.
* Remove <tuple> include.
* [C++] Use strong enum type for vectors when scoped-enums is on.
These changes only apply when scoped-enums is on, and thus only
the C++17 tests show diffs.
This may break users who use 1) use scoped-enums and 2) use
vectors of enums. However, it seems that this change should
have been made originally when scoped-enums were added.
Fixes#5285
* [C++] Put strong enum change also behind C++17 flag.
It actually only needs C++11 technically, but this is being done
to avoid breaking any existing users.
Tests were rerun, but produced no additional diffs, as expected.
* [C++] Forgot one location in which C++17 guard needs to go.
This commit produces no additional diffs in generated code.
* Use g_only_fixed_enums instead of scoped_enums.
* Include flattests_cpp17 in unit tests when C++17 build is enabled.
* [C++17] Generate generic table factory function.
1. For each table, generate a convenient free-standing factory
function that allows creating the table in a generic way by
specifying only the type. This is the first change in a series
of changes to make Flatbuffers generated C++ code more friendly
to code bases that make use of C++ template metaprogramming
techniques to manage the serialization process. Example:
Before :(
// The name of the Flatbuffers type (and namespace) must
// be hard-coded when writing the factory function.
auto monster = MyGame::Example::CreateMonster(fbb, ...);
After :)
using type_to_create = MyGame::Example::Monster;
// No namespace needed on CreateByTagType.
auto monster = CreateByTagType((type_to_create*)nullptr,
fbb, ...);
This feature requires building with C++14 or greater, and thus
it is guarded behind --cpp-std >= c++17 in the flatbuffers C++
generator.
2. Fix a CMake bug to include C++17 unit tests in test suite.
* [C++17] Replace standalone variadic factory function with type_traits.
Add a `type_traits` to each table class. This `type_traits` can be
populated with various compile-time info about the table. Initially,
we have the Create* function and type, but is extensible in the future.
* Remove empty line and fix stale comments.
* Rename type_traits to Traits and move fwd declaration.
* Fix parameter evaluation order issue and use lambda for scope.
dpacbach