appending to CFLAGS

[David Fleck]

4.9-RELEASE-p1.

I'm trying to debug a kernel module (vpo.ko) that used to work, but now
doesn't.  As a first step, I'd like to build the module in
/usr/src/sys/modules/vpo with VPO_DEBUG set.

However, my attempts to add the VPO_DEBUG define to the build fail,
because my syntax results in VPO_DEBUG replacing CFLAGS, not appended to
it.  I'm trying:

make "CFLAGS+=VPO_DEBUG"

in pretty much every permutation I can think of - quoted, unquoted,
whitespace separating tokens, no whitespace.  Each time, all the CFLAGS
are blown away and replaced by VPO_DEBUG.  How do I append a variable to
CFLAGS?

I'm sure this is something blindingly simple, but I'm not seeing it in the
developer's handbook or the make manpages.


--
David Fleck
david.fleck at mchsi.com