Intel® C++ Compiler 19.0 Developer Guide and Reference
Attributes are a way to provide additional information about a declaration to the compiler.
The Intel® compiler supports three ways to add attributes to your program:
__attribute__((attribute_name(arguments)))
__declspec(attribute_name(argument))
[[attribute_name(arguments)]]
[[attribute-namespace :: attribute_name(arguments)]]
Some attributes are available for both Intel® and non-Intel microprocessors but they may perform additional optimizations for Intel® microprocessors than they perform for non-Intel microprocessors. Refer to the individual attribute name for a detailed description.