build(cxx): align all builds on a C++14 baseline

[darion-yaphet]

What problem does this PR solve?

Issue Number: N/A

Problem Summary:
bRPC’s CMake and Make-based build paths used inconsistent C++11/C++14 settings. This establishes C++14 as the common minimum language level.

What is changed and the side effects?

Changed:

• Updated CMake, Make, test, tool, and example build settings to require C++14.
• Raised compiler checks to GCC 5.0+ and Clang 3.5+.
• Updated configuration and user-facing documentation.
• Preserved C++17 for Protobuf 22+ and Bazel.

Side effects:

• Performance effects: None expected.
• Breaking backward compatibility: C++11-only toolchains and build invocations are no longer supported.

———

Check List:

• Changes compile: clean CMake brpc-static build with AppleClang 16 and -std=gnu++14.
• Verified config_brpc.sh generation, shell syntax, and diff formatting.
• Unit test suite not run.
• No new feature behavior requiring tests.
• Follows the Contributor Covenant.

[Copilot]

Pull request overview

This PR standardizes bRPC’s non-Bazel build paths (CMake/Make/tests/examples/tools) on a C++14 minimum, updates compiler version gating accordingly, and refreshes related documentation so the baseline is consistent across the project.

Changes:

• Bumped build flags and CMake compile features/standards from C++11/C++0x to C++14 across tools, tests, and examples.
• Updated compiler version checks to require GCC 5.0+ / Clang 3.5+ (and adjusted supporting scripts).
• Updated docs and internal notes to reflect the C++14 baseline.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tools/trackme_server/Makefile	Switch tool build to -std=c++14.
tools/rpc_view/Makefile	Switch tool build to -std=c++14.
tools/rpc_replay/Makefile	Switch tool build to -std=c++14.
tools/rpc_press/Makefile	Switch tool build to -std=c++14.
tools/parallel_http/Makefile	Switch tool build to -std=c++14.
tools/print_gcc_version.sh	Update compiler detection/version reporting for new minimums (contains a Clang macro parsing bug; see comment).
THREAT_MODEL.md	Update security scope to require C++14 toolchain.
test/Makefile	Build unit tests with -std=c++14.
src/butil/type_traits.h	Enforce C++14+ at compile time in type-traits helpers.
example/ubring_performance/CMakeLists.txt	Raise example CMake standard to C++14.
example/thrift_extension_c++/Makefile	Switch example build to -std=c++14.
example/redis_c++/Makefile	Switch example build to -std=c++14.
example/rdma_performance/Makefile	Switch example build to -std=c++14.
example/multi_threaded_echo_c++/Makefile	Switch example build to -std=c++14.
example/memcache_c++/Makefile	Switch example build to -std=c++14.
example/http_c++/Makefile	Switch example build to -std=c++14.
example/echo_c++/Makefile	Switch example build to -std=c++14.
example/cmake/BrpcExample.cmake	Require cxx_std_14 for example targets.
docs/en/getting_started.md	Update supported compiler baseline / build instructions to C++14.
docs/cn/getting_started.md	Update supported compiler baseline / build instructions to C++14.
config_brpc.sh	Enforce GCC 5.0+ / Clang 3.5+ gate and set default -std=c++14 for non-Protobuf-22+ paths.
CMakeLists.txt	Raise minimum compiler versions and set BRPC C++ standard to 14.
CLAUDE.md	Update repository guidance to reflect C++14 minimum.

---

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[Copilot]

Pull request overview

Copilot reviewed 24 out of 24 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (16)

tools/trackme_server/Makefile:21

• This Makefile hard-codes -std=c++14 and also overwrites CXXFLAGS coming from config.mk. That defeats config_brpc.sh selecting -std=c++17 for Protobuf>=22 and can reintroduce inconsistent language levels across Make-based builds.

include $(BRPC_PATH)/config.mk
CXXFLAGS = $(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer
HDRPATHS = -I$(BRPC_PATH)/output/include $(addprefix -I, $(HDRS))

tools/rpc_view/Makefile:22

• This Makefile hard-codes -std=c++14 and overwrites CXXFLAGS from config.mk, which can defeat config_brpc.sh selecting -std=c++17 for Protobuf>=22 and reintroduce inconsistent language levels across Make-based builds.

CXXFLAGS = $(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

tools/rpc_replay/Makefile:20

• This Makefile overwrites CXXFLAGS from config.mk and hard-codes -std=c++14, which can defeat config_brpc.sh selecting -std=c++17 for Protobuf>=22 and cause inconsistent language levels across Make-based builds.

CXXFLAGS = $(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer -Wno-unused-parameter

tools/rpc_press/Makefile:20

• This Makefile overwrites CXXFLAGS from config.mk and hard-codes -std=c++14. That can defeat config_brpc.sh selecting -std=c++17 for Protobuf>=22 and reintroduce inconsistent language levels across Make-based builds.

CXXFLAGS = $(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer -Wno-unused-parameter

tools/parallel_http/Makefile:20

• This Makefile overwrites CXXFLAGS from config.mk and hard-codes -std=c++14, which can defeat config_brpc.sh selecting -std=c++17 for Protobuf>=22 and cause inconsistent language levels across Make-based builds.

CXXFLAGS = $(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer -Wno-unused-parameter

example/echo_c++/Makefile:23

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

example/http_c++/Makefile:23

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

example/multi_threaded_echo_c++/Makefile:23

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

example/rdma_performance/Makefile:24

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -D__const__=__unused__ -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

example/thrift_extension_c++/Makefile:23

• This Makefile overwrites CXXFLAGS from config.mk and hard-codes -std=c++14, which can defeat config_brpc.sh selecting -std=c++17 for Protobuf>=22 and cause inconsistent language levels between brpc and the example build.

CXXFLAGS = $(CPPFLAGS) -std=c++14 -g -DNDEBUG -O2 -pipe -W -Wall -Wno-unused-parameter -fPIC -fno-omit-frame-pointer

example/redis_c++/Makefile:20

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer

example/memcache_c++/Makefile:20

• This example Makefile appends -std=c++14 after including config.mk, which can override config_brpc.sh selecting -std=c++17 for Protobuf>=22 and lead to inconsistent language levels between brpc and the example build.

CXXFLAGS+=$(CPPFLAGS) -std=c++14 -DNDEBUG -O2 -pipe -W -Wall -fPIC -fno-omit-frame-pointer

tools/print_gcc_version.sh:33

• The grep pattern relies on \| alternation without using grep -E. \| is a non-POSIX extension and can fail on BSD/macOS grep (a supported platform), causing compiler detection to return 0 and config_brpc.sh to reject otherwise-valid compilers.

done < <("${CXX:-c++}" -dM -E - < /dev/null | grep "__clang__\|__clang_major__\|__clang_minor__\|__GNUC__\|__GNUC_MINOR__\|__GNUC_PATCHLEVEL__")

example/ubring_performance/CMakeLists.txt:76

• On CMake < 3.1.3, this only matches CMAKE_CXX_COMPILER_ID == "Clang" and misses AppleClang, so the example may build without any -std= flag on macOS and fail to compile. The top-level CMake uses MATCHES "Clang" for this reason.

    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")

docs/en/getting_started.md:327

• This sentence's rationale looks outdated: switching from C++11 to C++14 doesn’t affect the boost(atomic) dependency claim (C++11 already provides std::atomic). Consider rewording to state the actual requirement (C++14 minimum) rather than the old motivation.

c++14 is turned on by default to remove dependencies on boost (atomic).

docs/cn/getting_started.md:331

• 这里的表述沿用了原先“去除对 boost 的依赖（比如 atomic）”的理由，但将最低标准提升到 C++14 后，这个理由已不准确（C++11 就已有 std::atomic）。建议改为直接说明 bRPC 需要 C++14+。

默认启用 c++14，以去除对 boost 的依赖（比如 atomic）。

[wwbmmm]

LGTM

[chenBright]

I don't think this needs to be modified.