Node and Host Name Sizes on HP-UX: Using the Expanded Capabilities of HP-UX

In this case, the last two options will require explicit version attributes.

Explicit Version Attributes

Because interfaces that re-export constants do not inherit a version identifier, it is important to add one

explicitly. The version attribute macro defined in sys/stdsyms.h can be used for this purpose.

For example:

#include <sys/stdsyms.h>

#if _INCLUDE_HPUX_API_LEVEL >= 20040821

# if MAXHOSTNAMELEN != 256

error MAXHOSTNAMELEN and API level mismatch /* sanity check */

# endif

#define UVW_ATTR _HPUX_API_VERS_20040821_ATTR /* version attribute */

#else

#define UVW_ATTR /* no version attribute */

# if MAXHOSTNAMELEN != 64

error MAXHOSTNAMELEN and API level mismatch /* sanity check */

# endif

#endif

struct UVW_ATTR uvw {

int uvw_field1;

char uvw_host[MAXHOSTNAMELEN];

}

extern int get_uvw(struct uvw *) UVW_ATTR;

Note that the function get_uvw(), because it has a versioned type as a parameter, automatically

inherits the version identifier from struct uvw. An explicit attribute is not required but is added for

clarity.

The sanity checks provide some compile-time checking that the declarations have been laid out

consistently with the OS headers.

Constants: Providing Multiple Versions

The manner in which multiple versions are provided depends on the design of the code that provides

the get_uvw() interface. Either a parallel implementation approach or a thin converter might be

practical. See “Providing Multiple Versions in a Library”.

With re-export of constants, it might be necessary to add explicit version attributes in the supporting

code.