intro(3attr) intro(3attr) intro - C/C++ [[attr]] [[vendor::attr]] . vendor . C C++ . __attribute__((attr)) GNU . GCC Clang. __declspec(attr) MSVC . Clang. C23, C++23. [[attr]] [[vendor::attr]] C23, C++11. [[attr]] [[gnu::attr]] gcc 10, g++ 9, clang 9, clang++ 9. __attribute__((attr)) gcc, g++, clang, clang++. __declspec(attr) clang, clang++. 3 . . : . 6.18 28 2025 intro(3attr)