protobuf

Commit Graph

Author	SHA1	Message	Date
Joshua Haberman	e41a2d7ba0	upb is self-hosting! This CL changes the upb compiler to no longer depend on C++ protobuf libraries. upb now uses its own reflection libraries to implement its code generator. # Key Benefits 1. upb can now use its own reflection libraries throughout the compiler. This makes upb more consistent and principled, and gives us more chances to dogfood our own C++ reflection API. This highlighted several parts of the C++ reflection API that were incomplete. 2. This CL removes code duplication that previously existed in the compiler. The upb reflection library has code to build MiniDescriptors and MiniTables out of descriptors, but prior to this CL the upb compiler could not use it. The upb compiler had a separate copy of this logic, and the compiler's copy of this logic was especially tricky and hard to maintain. This CL removes the separate copy of that logic. 3. This CL (mostly) removes upb's dependency on the C++ protobuf library. We still depend on `protoc` (the binary), but the runtime and compiler no longer link against C++'s libraries. This opens up the possibility of speeding up some builds significantly if we can use a prebuilt `protoc` binary. # Bootstrap Stages To bootstrap, we check in a copy of our generated code for `descriptor.proto` and `plugin.proto`. This allows the compiler to depend on the generated code for these two protos without creating a circular dependency. This code is checked in to the `stage0` directory. The bootstrapping process is divided into a few stages. All `cc_library()`, `upb_proto_library()`, and `cc_binary()` targets that would otherwise be circular participate in this staging process. That currently includes: * `//third_party/upb:descriptor_upb_proto` * `//third_party/upb:plugin_upb_proto` * `//third_party/upb:reflection` * `//third_party/upb:reflection_internal` * `//third_party/upbc:common` * `//third_party/upbc:file_layout` * `//third_party/upbc:plugin` * `//third_party/upbc:protoc-gen-upb` For each of these targets, we produce a rule for each stage (the logic for this is nicely encapsulated in Blaze/Bazel macros like `bootstrap_cc_library()` and `bootstrap_upb_proto_library()`, so the `BUILD` file remains readable). For example: * `//third_party/upb:descriptor_upb_proto_stage0` * `//third_party/upb:descriptor_upb_proto_stage1` * `//third_party/upb:descriptor_upb_proto` The stages are: 1. `stage0`: This uses the checked-in version of the generated code. The stage0 compiler is correct and outputs the same code as all other compilers, but it is unnecessarily slow because its protos were compiled in bootstrap mode. The stage0 compiler is used to generate protos for stage1. 2. `stage1`: The stage1 compiler is correct and fast, and therefore we use it in almost all cases (eg. `upb_proto_library()`). However its own protos were not generated using `upb_proto_library()`, so its `cc_library()` targets cannot be safely mixed with `upb_proto_library()`, as this would lead to duplicate symbols. 3. final (no stage): The final compiler is identical to the `stage1` compiler. The only difference is that its protos were built with `upb_proto_library()`. This doesn't matter very much for the compiler binary, but for the `cc_library()` targets like `//third_party/upb:reflection`, only the final targets can be safely linked in by other applications. # "Bootstrap Mode" Protos The checked-in generated code is generated in a special "bootstrap" mode that is a bit different than normal generated code. Bootstrap mode avoids depending on the internal representation of MiniTables or the messages, at the cost of slower runtime performance. Bootstrap mode only interacts with MiniTables and messages using public APIs such as `upb_MiniTable_Build()`, `upb_Message_GetInt32()`, etc. This is very important as it allows us to change the internal representation without needing to regenerate our bootstrap protos. This will make it far easier to write CLs that change the internal representation, because it avoids the awkward dance of trying to regenerate the bootstrap protos when the compiler itself is broken due to bootstrap protos being out of date. The bootstrap generated code does have two downsides: 1. The accessors are less efficient, because they look up MiniTable fields by number instead of hard-coding the MiniTableField into the generated code. 2. It requires runtime initialization of the MiniTables, which costs CPU cycles at startup, and also allocates memory which is never freed. Per google3 rules this is not really a leak, since this memory is still reachable via static variables, but it is undesirable in many contexts. We could fix this part by introducing the equivalent of `google::protobuf::ShutdownProtobufLibrary()`). These downsides are fine for the bootstrapping process, but they are reason enough not to enable bootstrap mode in general for all protos. # Bootstrapping Always Uses OSS Protos To enable smooth syncing between Google3 and OSS, we always use an OSS version of the checked in generated code for `stage0`, even in google3. This requires that the google3 code can be switched to reference the OSS proto names using a preprocessor define. We introduce the `UPB_DESC(xyz)` macro for this, which will expand into either `proto2_xyz` or `google_protobuf_xyz`. Any libraries used in `stage0` must use `UPB_DESC(xyz)` rather than refer to the symbol names directly. PiperOrigin-RevId: 501458451	2 years ago
Mike Kruskal	2b011bc759	Internal changes PiperOrigin-RevId: 487599716	2 years ago
Eric Salo	f6307877d3	move portability stuff into upb/port/ Also delete redundant system #includes that are already pulled in by port/def.inc PiperOrigin-RevId: 486398989	2 years ago
Eric Salo	44916d7d27	create reflection_internal library internal declarations are now physically removed from the public headers PiperOrigin-RevId: 478921131	2 years ago
Eric Salo	edecfd5eb0	upb: use the new reflection headers Reflection headers now live in upb/reflection/ so update our include statements to reflect this. (See what I did there?) PiperOrigin-RevId: 474596615	2 years ago
Samuel Benzaquen	8d755661aa	Update protoc-gen-upbdefs.cc	3 years ago
Joshua Haberman	1c955f37ce	Mass API rename and clang-reformat (#485 ) * Wave 1: upb_fielddef. * upb_fielddef itself. * upb_oneofdef. * upb_msgdef. * ExtensionRange. * upb_enumdef * upb_enumvaldef * upb_filedef * upb_methoddef * upb_servicedef * upb_symtab * upb_defpool_init * upb_wellknown and upb_syntax_t * Some constants. * upb_status * upb_strview * upb_arena * upb.h constants * reflection * encode * JSON decode. * json encode. * msg_internal. * Formatted with clang-format. * Some naming fixups and comment reformatting. * More refinements. * A few more stragglers. * Fixed PyObject_HEAD with semicolon. Removed TODO entries.	3 years ago
Joshua Haberman	ce012b7b55	Added support for extensions.	3 years ago
Joshua Haberman	823eb09694	Update all 2011 dates to 2021.	4 years ago
Joshua Haberman	e59d2c8fa7	Added license headers to all files.	4 years ago
Joshua Haberman	7a54a5f3d6	Split the code generators for .upb and .upbdefs. Before there was a single code generator that generated both .upb and .upbdefs, even though they are generated by different rules. This worked fine as long as the codegen steps were sandboxed, but if not it led to build errors. Fixes https://github.com/protocolbuffers/upb/issues/354.	4 years ago

11 Commits (7ebeb6006bff5ea7bedbea9769d03fff4286bdda)