/EXTERN_MODEL
       /EXTERN_MODEL=option
       /EXTERN_MODEL=RELAXED_REFDEF (D)

    In conjunction with the /SHARE_GLOBALS qualifier, controls the
    initial extern model of the compiler. Conceptually, the compiler
    behaves as if the first line of the program being compiled was a
    #pragma extern_model directive with the model and psect name, if
    any, specified by the /EXTERN_MODEL qualifier and with the SHR or
    NOSHR keyword specified by the /SHARE_GLOBALS qualifier.

    For example, assume the command line contains the following
    qualifier:

    /EXTERN_MODEL=STRICT_REFDEF="MYDATA"/NOSHARE

    The compiler acts as if the program began with the following
    line:

          #pragma extern_model strict_refdef "MYDATA" noshr

    For more information on the various models, see "C++
    Implementation" in the HP C++ User's Guide for OpenVMS Systems.

    The /EXTERN_MODEL qualifier takes the following options, which
    have the same meaning as for the #pragma extern_model directive:

       COMMON_BLOCK
       RELAXED_REFDEF
       STRICT_REFDEF=["NAME"]
       GLOBALVALUE

    The default is RELAXED_REFDEF.

    Use of an /EXTERN_MODEL value other than RELAXED_REFDEF should
    be limited to compilations that either declare only POD (Plain
    Old Data) objects, or that carefully use the extern_model (and/or
    environment) #pragma directives to ensure that declarations of
    non-POD objects appear only in source that is subject to the
    default extern_model of relaxed_refdef.