Add optional standalone CMake component libraries

[wasphin]

What problem does this PR solve?

Issue Number: N/A

Problem Summary:

CMake currently packages the production modules into the brpc bundle. Applications
that only need butil, bvar, bthread, json2pb or mcpack2pb cannot consume an installed
component target independently, which also prevents packaging these modules for
standalone use through vcpkg.

What is changed and the side effects?

Changed:

Merge preference: Please use Rebase and merge rather than Squash and merge
to preserve the four focused commits and the step-by-step migration history.

The four commits separate directory ownership, target ownership, component
packaging and mcpack IDL ownership so each stage can be reviewed independently:

1. Move production source definitions into their module directories.
2. Define module-owned object targets, scope feature/dependency handling to the
   owning modules and reuse those targets for the legacy bundles and tests.
3. Add optional component libraries and exported CMake package targets.
4. Make mcpack2pb own the IDL option schema, generated public header and symbols,
   updating CMake, Make and Bazel rules without changing public import names.

• BRPC_BUILD_COMPONENT_LIBS is OFF by default. Enabling it builds all six
  components alongside the existing bundle; BUILD_SHARED_LIBS controls the
  standalone libraries' linkage.
• Export brpc::butil, brpc::bvar, brpc::bthread, brpc::json2pb,
  brpc::mcpack2pb and brpc::brpc with their transitive dependencies.
  The RPC-only library is named libbrpc-rpc to avoid conflicting with the
  existing libbrpc bundle.
• Install headers directly from module source/build directories and use target
  build/install interfaces instead of staging copies in output/include.
• Keep generated IDL definitions in mcpack2pb and obtain them transitively from
  the RPC component. Preserve import "idl_options.proto" and
  #include "idl_options.pb.h".
• Do not distribute producer-side custom Find modules in the installed package.
• Add six standalone consumer checks, including custom-option consumption and a
  complete RPC client/server exchange using an ephemeral server port.
• Export UMDK headers for URMA mock consumers without requiring liburma;
  exercise static and shared mock packages in existing all-options CI jobs.
• Configure CMake examples through an explicit installation prefix instead of
  searching for the removed output/include staging directory.
• Update both English and Chinese getting-started documentation, including an
  independent vcpkg consumer example. The documented components feature is
  provided by an overlay port, not the current registry port.

Side effects:

• Performance effects: Production objects are compiled once and reused by the
  bundle and standalone libraries. Enabling components adds library linking and
  packaging work; it does not duplicate production source compilation.

• Breaking backward compatibility: Existing bundle names and linkage remain
  unchanged, and standalone components are opt-in. CMake builds no longer stage
  headers in output/include; users relying on that directory should run
  cmake --install build --prefix build/output. Do not link the bundle and
  standalone components into the same application because they share symbols.

---

Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[Copilot]

🟡 Changes recommended

Shared component objects lack required PIC settings, URMA mock packages omit public headers, and consumer checks are not automated.

3 open findings

• Enable PIC for PROTO_LIB object files · New
• Enable PIC for IDL_OPTIONS_LIB object files · New
• Add CI coverage for component library consumer checks · New

What changed in this PR

Adds opt-in standalone CMake libraries for bRPC modules while preserving the legacy bundle.

Changes:

• Introduces six exported component targets with transitive dependencies.
• Moves CMake ownership into module directories and relocates mcpack IDL ownership.
• Adds consumer checks, packaging support, and updated documentation.

File	Description
CMakeLists.txt	Adds component option and delegates module builds.
Makefile	Updates mcpack IDL generation and installation.
BUILD.bazel	Relocates the mcpack IDL schema.
cmake/​bRPCComponents.cmake	Defines component and export helpers.
cmake/​bRPCHeaders.cmake	Installs module-owned headers.
cmake/​brpc-config.cmake.in	Configures component discovery and dependencies.
cmake/​CompileProto.cmake	Removes staged protobuf-header copies.
cmake/​SetupGtest.cmake	Uses module-relative template lookup.
src/​CMakeLists.txt	Aggregates module objects into legacy bundles.
src/​brpc/​CMakeLists.txt	Defines RPC objects, dependencies, and component.
src/​bthread/​CMakeLists.txt	Defines the bthread component.
src/​butil/​CMakeLists.txt	Defines butil sources and dependencies.
src/​butil/​config.h.in	Adds generated butil feature configuration.
src/​bvar/​CMakeLists.txt	Defines the bvar component.
src/​json2pb/​CMakeLists.txt	Defines the json2pb component.
src/​mcpack2pb/​CMakeLists.txt	Defines mcpack2pb and IDL targets.
src/​mcpack2pb/​idl_options.proto	Moves the public IDL option schema.
test/​CMakeLists.txt	Adapts tests to module-owned targets.
test/​Makefile	Adds the relocated schema import path.
test/​cmake_components/​CMakeLists.txt	Defines standalone consumer checks.
test/​cmake_components/​consumer.cpp	Exercises all component targets.
test/​cmake_components/​echo.proto	Supplies the RPC consumer schema.
test/​cmake_components/​mcpack.proto	Exercises custom mcpack options.
tools/​rpc_press/​CMakeLists.txt	Uses directory-local source discovery.
tools/​rpc_replay/​CMakeLists.txt	Uses directory-local source discovery.
example/​cmake/​BrpcExample.cmake	Makes example discovery directory-relative.
example/​dynamic_partition_echo_c++/​CMakeLists.txt	Fixes local resource copying.
example/​http_c++/​CMakeLists.txt	Fixes certificate copying.
example/​multi_threaded_echo_c++/​CMakeLists.txt	Fixes certificate copying.
example/​partition_echo_c++/​CMakeLists.txt	Fixes server-list copying.
example/​ubring_performance/​CMakeLists.txt	Makes output discovery directory-relative.
docs/​en/​getting_started.md	Documents components and vcpkg consumption.
docs/​cn/​getting_started.md	Adds equivalent Chinese documentation.

🧠 Review effort: Balanced

---

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[Copilot]

🟡 Changes recommended

Optional-feature and macOS component package paths lack consumer-level CI coverage.

2 open findings

• Add consumer coverage for optional components and macOS builds · New
• Add CI coverage for component library consumer checks

2 resolved since last review

• Enable PIC for IDL_OPTIONS_LIB object files
• Enable PIC for PROTO_LIB object files

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

The Zvbc CMake scoping omits several RVV callers and implementations, disabling paths and potentially leaving missing symbols.

2 open findings

• Apply RISC-V vector flags to all RVV-dependent sources · New
• Apply RISC-V vector flags consistently in debug builds · New

2 resolved since last review

• Add consumer coverage for optional components and macOS builds
• Add CI coverage for component library consumer checks

🧠 Review effort: Balanced

[wasphin]

The fix restores the previous target-wide ISA setting for GNU RISC-V builds. With WITH_RISCV_ZVBC=ON, brpc_common_config supplies -march=rv64gcv_zbc_zvbc to the internal module build configurations, covering the CRC32C and base64 implementations as well as modp_b64.cc, iobuf.cpp, string_piece.cc, and string_compare_rvv.cc. This setting is not conditional on the build type.

I checked the generated compile commands for the Zvbc, Zbc-only, and baseline configurations, including the test debug-object targets. This was configure-only validation, not a RISC-V compile or runtime test. I am leaving this thread open pending a real GNU RISC-V build with WITH_RISCV_ZVBC=ON, including Debug/test objects, followed by the affected tests.

[wasphin]

The test debug-object targets now inherit the same ISA options as production through brpc_test_config -> brpc_build_config -> the module configurations -> brpc_common_config. The partial per-source RISC-V assignments have been removed, so BUTIL_DEBUG_LIB gets the architecture setting for the complete source list, including the RVV callers and implementations.

Generated compile-command checks confirmed the option reaches these debug objects. However, I have not performed a real RISC-V build, and those checks were not a completed Debug build. I am leaving this thread open; the remaining validation is an actual GNU RISC-V Debug build with WITH_RISCV_ZVBC=ON and the affected tests.

[Copilot]

🟡 Changes recommended

The build-tree mcpack2pb export does not expose the relocated public IDL schema.

3 open findings

• Apply RISC-V vector flags consistently in debug builds
• Apply RISC-V vector flags to all RVV-dependent sources
• Build-tree consumers cannot resolve idl_options.proto · New

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

The generated butil configuration header is shared through the source tree, allowing different build directories to overwrite each other’s configuration.

3 open findings

• Apply RISC-V vector flags consistently in debug builds
• Apply RISC-V vector flags to all RVV-dependent sources
• Generate config.h in build tree to prevent cross-build conflicts · New

1 resolved since last review

• Build-tree consumers cannot resolve idl_options.proto

🧠 Review effort: Balanced

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[Copilot]

🔵 Needs a closer look

Cross-build-system packaging needs human validation, and URMA header exports and example builds remain unresolved.

4 open findings

• Export URMA headers for mock builds without requiring liburma · New
• Apply RISC-V vector flags consistently in debug builds
• Apply RISC-V vector flags to all RVV-dependent sources
• Update examples for removed output/include build path · New

1 resolved since last review

• Generate config.h in build tree to prevent cross-build conflicts

🧠 Review effort: Lite

[wwbmmm]

[replied by brpc-oncall robot] The latest revision resolves the examples and URMA findings and looks functionally sound; the remaining concern is the hand-maintained optional-dependency discovery in the installed config, which will keep drifting from the module CMakeLists.

[wwbmmm]

[replied by brpc-oncall robot] brpc-config.cmake.in still hand-reimplements discovery for gflags/leveldb/OpenSSL/BoringSSL/glog/thrift/rdma/snappy/urma/unwind with bespoke find_library/find_path blocks, duplicating the logic that now lives in the per-module CMakeLists (src/butil, src/brpc, src/bthread). Each optional dependency must be kept in sync across the module files, this template and the pkg-config strings, and the URMA mock/real split shows how quickly this grows. Consider deriving the exported dependency list from the component targets, or at least documenting the sync points next to these loops, so a new WITH_* feature cannot silently be handled in only some of them.