The goal of the `names.h` convention is to have a single canonical place where a code generator can define the set of symbols it exports to other code generators, and a canonical place where the name mangling logic is implemented.
Each upb code generator now has its own `names.h` file defining the symbols that it owns & exports:
* `third_party/upb/upb_generator/c/names.h` (for `foo.upb.h` files)
* `third_party/upb/upb_generator/minitable/names.h` (for `foo.upb_minitable.h` files)
* `third_party/upb/upb_generator/reflection/names.h` (for `foo.upbdefs.h` files)
This is a significant improvement over the previous situation where the name mangling functions were co-mingled in `common.h`/`mangle.h`, or sprinkled throughout the generators, with no clear structure for which code generator owns which symbols.
With this structure in place, the visibility lists for the various `names.h` files provide a clear dependency graph for how different generators depend on each other. In general, we want to keep dependencies on the "C" code generator to a minimum, since it is the largest and most complicated of upb's generated APIs, and is also the most prone to symbol name clashes.
Note that upb's `names.h` headers are somewhat unusual, in that we do not want them to depend on C++'s reflection or upb's reflection. Most `names.h` headers in protobuf would use types like `proto2::Descriptor`, but we don't want upb to depend on C++ reflection, especially during its bootstrapping process. We also don't want to force users to build upb defs just to use these name mangling functions. So we use only plain string types like `absl::string_view` and `std::string`.
PiperOrigin-RevId: 672397247
Our bootstrapping setup compiles multiple versions of the generated code for `descriptor.proto` and `plugin.proto`, one for each stage of the bootstrap. For source files (`.c`), we can always select the correct version of the file in the BUILD rules, but for header files we need to make sure the correct stage's file is always selected via `#include`.
Previously we used `cc_library(includes=[])` to make it appear as though our bootstrapped headers had the same names as the "real" headers. This allowed a lot of the code to be agnostic to whether a bootstrap header was being used, which simplified things because we did not have to change the code performing the `#include`.
Unfortunately, due to build system limitations, this sometimes led to the incorrect header getting included. This should not have been possible, because we had a clean BUILD graph that should have removed all ambiguity about which header should be available. But in non-sandboxed builds, the compiler was able to find headers that were not actually in `deps=[]`, and worse it preferred those headers over the headers that actually were in `deps=[]`. This led to unintended results and errors about layering check violations.
This CL fixes the problem by removing all use of `includes=[]`. We now spell a full pathname to all bootstrap headers, so this class of errors is no longer possible. Unfortunately this adds some complexity, as we have to hard-code these full paths in several places.
A nice improvement in this CL is that `bootstrap_upb_proto_library()` can now only be used for bootstrapping; it only exposes the `descriptor_bootstrap.h` / `plugin_bootstrap.h` files. Anyone wanting to use the normal `net/proto2/proto/descriptor.upb.h` file should depend on `//net/proto2/proto:descriptor_upb_c_proto` target instead.
PiperOrigin-RevId: 664953196
The functionality is enabled when the proto_one_output_per_message option used by C++ Lite is enabled.
This mirrors the behavior of C++ lite protos.
PiperOrigin-RevId: 642327960
The functionality is enabled when the `proto_one_output_per_message` option used by C++ Lite is enabled.
This mirrors the behavior of C++ lite protos.
PiperOrigin-RevId: 640592937
Joshua Haberman
Mike Kruskal
Protobuf Team Bot