I actually installed everything manually -- downloaded source
  packages of gnu make 3.80, autoconf 2.59, automake 1.9.6, libtool
  1.5.8, readline 5.1, m4 1.4. did the usual ./configure;make;make
  install routine for well-behaved programs. everything built fine
  with no errors & i've used the tools to build other software
  packages e.g. SSH, BIND, Apache

Not really relevant to coda, but I'm baffled as to why you don't use
pkgsrc.  It automates all of this.

  (gdb) up
  #1  0x0008f2a8 in coda_assert (
      pred=0xf9e <Error reading address 0xf9e: Invalid argument>,
      file=0x94518 "srv.cc", line=302) at coda_assert.c:46
  46                   sleep(1);
  Current language:  auto; currently c

Sorry, I meant to move up until you found the frame with the real
problem.  But if you aren't used to debugging with gdb this isn't
going to work over email.

  (gdb) bt
  #0  0x403bc3a0 in sleep () from /usr/local/lib/libc.so.12
  #1  0x0008f2a8 in coda_assert (
      pred=0xf9e <Error reading address 0xf9e: Invalid argument>,
      file=0x94518 "srv.cc", line=302) at coda_assert.c:46
  #2  0x00013c64 in zombie(int) (sig=3998) at srv.cc:302
  #3  <signal handler called>

Ah, the trace ends at the signal handler, but the real question is why
the signal happened.  Perhaps you can run the server under gdb to
start with, so it breaks when the signal hits.

  Never ran into any make errors using gmake. I think using BSD make
  instead gives "missing seperator" errors or some other syntax-y thing.

Sorry, I thought you used BSD make since your example said "make" and
GNU make is built as gmake by pkgsrc.

  I just ln -s /usr/lib /usr/local/lib; ln -s /usr/include
  /usr/local/include to put any silliness about lost libs or includes
  to rest; besides, didn't get any of the usual errors associated with
  bad libs or headers such as compilation errors or successful build
  but undefined symbol on run...

That is in my view asking for trouble.  Using pkgsrc for dependencies
and my build script will get you aligned with how most people on
NetBSD do things.

-- 
        Greg Troxel <gdt_at_ir.bbn.com>