Deprecated language features are not expected to appear in future Common Lisp tandards, but are required to be implemented for conformance with this standard; see Section 184.108.40.206 (Required Language Features).
Conforming programs can use deprecated features; however, it is considered good programming style to avoid them. It is permissible for the compiler to produce style warnings about the use of such features at compile time, but there should be no such warnings at program execution time.
1.8.1 Deprecated Functions
1.8.2 Deprecated Argument Conventions
1.8.3 Deprecated Variables
1.8.4 Deprecated Reader Syntax