__has_cpp_attribute (The C Preprocessor)

#### 4.2.7 `__has_cpp_attribute` ¶

The special operator `__has_cpp_attribute (operand)` may be used in ‘`#if`’ and ‘`#elif`’ expressions in C++ code to test whether the attribute referenced by its operand is recognized by GCC. `__has_cpp_attribute (operand)` is equivalent to `__has_attribute (operand)` except that when operand designates a supported standard attribute it evaluates to an integer constant of the form `YYYYMM` indicating the year and month when the attribute was first introduced into the C++ standard. For additional information including the dates of the introduction of current standard attributes, see SD-6: SG10 Feature Test Recommendations.