Like
.Fl Wshadow ,
but only warn if the shadowed declaration is not global, e.g. a local variable shadows a parameter or another local variable.
+.It Fl Wsystem
+Show warnings in system headers.
+By default, no warnings in system headers are shown.
.It Fl Wunreachable-code
Warn when the compiler determines that a statement (or in some cases a part thereof) will never be executed.
.It Fl Wunused