Causes ftnchek to report whether any subprograms
invoked by the program are never defined.
Ordinarily, if ftnchek is being run on a complete program, each
subprogram other than the intrinsic functions should be defined
somewhere. Turn off this switch if you just want to
check a subset of files which form part of a larger complete program.
Subprogram arguments will still be
checked for correctness. Default = yes.
The -extern flag is now superseded by the
-usage=ext-undefined option. For the sake of convenience, the
-extern flag is retained, so that -noextern is
equivalent to -usage=no-ext-undefined option. The
-extern switch may be retired eventually.
See also: -library.