malloc

    OpenVMS usage: function_value
    type:          procedure
    access:        read
    mechanism:     by value

    A procedure value for a user callback routine that allocates
    memory. This is an optional argument. The default is to use an
    implementation of the C RTL routine malloc. If specified, this
    routine is used to allocate the invocation context block and is
    also placed in the LIBICB$PH_UO_MALLOC invocation context block
    field for use during the stack walk.

 free

    OpenVMS usage: function_value
    type:          procedure
    access:        read
    mechanism:     by value

    A procedure value for a user callback routine that deallocates
    memory. This value is placed in the invocation context block
    field LIBICB$PH_UO_FREE. This is an optional argument, however,
    it must be specified if malloc is set. The default is to use an
    implementation of the C RTL routine free.

 ident

    OpenVMS usage: user_value
    type:          quadword
    access:        read
    mechanism:     by value

    Specifies a user ident value to be placed in the invocation
    context block LIBICB$IH_UO_IDENT field. In turn, this value is
    passed to the malloc and free routines. This is an optional
    argument; the default value is zero.