csup and build question

[perryh at pluto.rain.com]

Bruce Cran <bruce at cran.org.uk> wrote:
> On Sat, 1 Jan 2011 20:44:01 +0100
> Polytropon <freebsd at edvax.de> wrote:
> > If programs or other components of the world do have to
> > be in sync with kernel or system files (sys/*.h), then
> > I conclude that world also has to be compiled. In this
> > regards, it means a change of the kernel, and if the
> > kernel did change, kernel and world are out of sync,
> > which implies that both have to be compiled.
> The ABI of the kernel sometimes changes, in which case despite
> there being no changes in world it still needs to be rebuilt
> against the newer header files. For example, recently:
>
> 20101228:
> 	The TCP stack has been modified to allow Khelp modules to
> interact with it via helper hook points and store per-connection
> data in the TCP control block. Bump __FreeBSD_version to 900029.
> User space tools that rely on the size of struct tcpcb in tcp_var.h
> (e.g. sockstat) need to be recompiled.

IIUC, things like that are supposed to happen only within -CURRENT,
not within a -STABLE or security branch.

I would surmise that, if a csup yielded changes only in /usr/src/sys
and none of those changes touched a .h file, it should not be necessary
to rebuild world.