Fix GCC 16 compile Error

[pynj2026]

What problem does this PR solve?

Issue Number: No

Problem Summary:

What is changed and the side effects?

Changed:

• The -D__STRICT_ANSI__ in CMakeLists.txt conflicts with libstdc++ 16's __int128 specialization

• H2StreamContext is incomplete, so sizeof throws an error, causing unique_ptr to fail

Side effects:

• Performance effects:
  No
• Breaking backward compatibility:
  No

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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]

Copilot review overview

🔵 Needs a closer look

GCC 16 build compatibility remains unverified and needs target-toolchain validation before approval.

Review effort: Balanced
Findings: None

What changed in this PR

Addresses GCC 16 compilation issues in bRPC’s CMake configuration and HTTP/2 request handling.

Changes:

• Adds a compile probe before defining __STRICT_ANSI__.
• Moves H2UnsentRequest construction and destruction out of the header to resolve incomplete-type errors.

File	Description
src/​brpc/​policy/​http2_rpc_protocol.h	Replaces inline constructor and destructor definitions with declarations.
src/​brpc/​policy/​http2_rpc_protocol.cpp	Defines the constructor and destructor where the stream type is complete.
CMakeLists.txt	Conditionally enables __STRICT_ANSI__ based on compilation support.

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[wwbmmm]

LGTM

[wasphin]

Could we simply remove the explicit __STRICT_ANSI__ definition instead of adding a configure-time probe?

We should let the compiler define this macro according to the selected language mode. Neither the Make nor Bazel build explicitly defines it; their -std=c++14/-std=c++17 options let the compiler set it automatically. Manually defining it in GNU mode can make standard-library headers see a mode that does not match the compiler settings.

I traced the CMake definition to commit 9b6b004 (2017), whose main change was to avoid compiling sources twice. It did not document a specific requirement for this macro, and I found no brpc source code checking it directly. Removing the manual definition would avoid the reported libstdc++ 16 conflict without introducing another configuration check. If strict ISO mode is intended, it should be selected through CMake language-mode settings rather than by forcing the macro.

[Copilot]

Copilot review overview

🟢 Approval recommended

Static review found no blocking issues in these focused compatibility fixes, though GCC 16 compilation was not executed.

Review effort: Balanced
Findings: None

[wasphin]

LGTM