Re: [gpsd-dev] Warnings from 32 bit FreeBSD

[Greg Troxel]

I wonder how much of this feature test macro stuff can be avoided by
just *not defining* _XOPEN_SOURCE in the first place.

Generally, my impression is that most systems make available all of
their definitions if no feature macros are defined.  And if some are,
such as one that specifies a standard, then definitionss not specified
in that standard are hidden.  This is useful when writing strictly to a
standard, so that non-standard calls can be removed.

It may be that some systems (this seems more solarisy, from my very hazy
memory), hide things that we expect unless something like _XOPEN_SOURCE
is defined.

Overall, your approach  to centralize this and to define _NETBSD_SOURCE
and other similar things, per system, to get back the normal visibility
sounds reasonable.