I'm getting these warnings from gcc 4.6.1. Some of these look like bugs (e.g. src/libthread/iorw.c:167).
* Building everything (be patient)...
>>> cd /usr/local/plan9/src/libhtml; mk all
9c build.c
build.c:4536:14: warning: variable ‘c’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/libmach; mk all
9c -I. manglegcc2.c
manglegcc2.c:364:30: warning: variable ‘p1’ set but not used [-Wunused-but-set-variable]
manglegcc2.c:364:25: warning: variable ‘p0’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/libmach; mk all
9c -I. symstabs.c
symstabs.c:128:6: warning: variable ‘locals’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/libsunrpc; mk all
9c udp.c
udp.c:85:9: warning: variable ‘buf’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/libsunrpc; mk all
9c nfs3.c
nfs3.c:123:21: warning: comparison between ‘SunStatus’ and ‘Nfs3Status’ [-Wenum-compare]
>>> cd /usr/local/plan9/src/libthread; mk all
9c -o iorw.o -I. iorw.c
iorw.c:167:6: warning: variable ‘r’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd; mk all
9c 9p.c
9p.c:500:6: warning: variable ‘nf’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd; mk all
9c join.c
join.c:308:15: warning: array subscript is above array bounds [-Warray-bounds]
>>> cd /usr/local/plan9/src/cmd; mk all
9c ramfs.c
ramfs.c:141:8: warning: variable ‘defmnt’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/acid; mk all
9c main.c
main.c:58:6: warning: variable ‘pid’ set but not used [-Wunused-but-set-variable]
main.c:193:15: warning: variable ‘pid’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/acidtypes; mk all
9c -I../../libmach stabs.c
stabs.c:315:39: warning: variable ‘bits’ set but not used [-Wunused-but-set-variable]
stabs.c:315:6: warning: variable ‘ischar’ set but not used [-Wunused-but-set-variable]
stabs.c:606:11: warning: variable ‘file’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/acme; mk all
9c rows.c
rows.c:105:13: warning: variable ‘odx’ set but not used [-Wunused-but-set-variable]
rows.c:105:9: warning: variable ‘dx’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/acme; mk all
9c wind.c
wind.c:145:38: warning: variable ‘tagresized’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/auth; mk all
9c dsagen.c
dsagen.c:17:6: warning: variable ‘bits’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/auth; mk all
9c rsa2any.c
rsa2any.c:167:6: warning: variable ‘regen’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/auth; mk all
9c ssh-agent.c
ssh-agent.c:932:6: warning: variable ‘n’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/auth/factotum; mk all
9c p9cr.c
p9cr.c:58:6: warning: variable ‘astype’ set but not used [-Wunused-but-set-variable]
>>> cd lib; mk
9c -DPLAN9 compress.c
compress.c:289:19: warning: variable ‘nBytes’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/db; mk all
9c print.c
print.c:96:8: warning: variable ‘r’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/devdraw; mk all
9c -I/usr/include x11-get.c
x11-get.c:59:6: warning: variable ‘offset’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/ndb; mk all
9c dn.c
dn.c:465:15: warning: variable ‘lastclean’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/page; mk all
9c rotate.c
rotate.c:88:16: warning: variable ‘r1’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/pic; mk all
9c linegen.c
linegen.c:23:13: warning: variable ‘chop_ap’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/pic; mk all
9c textgen.c
textgen.c:11:16: warning: variable ‘prevw’ set but not used [-Wunused-but-set-variable]
textgen.c:10:16: warning: variable ‘prevh’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/postscript/tr2post; mk all
9c -c -DPROGRAMVERSION="0.1" -DDOROUND=1 -I../common chartab.c
chartab.c:133:37: warning: variable ‘endchar’ set but not used [-Wunused-but-set-variable]
chartab.c:133:26: warning: variable ‘startchar’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/postscript/tr2post; mk all
9c -c -DPROGRAMVERSION="0.1" -DDOROUND=1 -I../common utils.c
utils.c:245:6: warning: variable ‘i’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/tpic; mk all
9c textgen.c
textgen.c:12:16: warning: variable ‘prevw’ set but not used [-Wunused-but-set-variable]
textgen.c:11:16: warning: variable ‘prevh’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/troff; mk all
9c -DUNICODE t6.c
t6.c:220:6: warning: variable ‘j’ set but not used [-Wunused-but-set-variable]
t6.c:714:37: warning: variable ‘sl’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/troff; mk all
9c -DUNICODE n6.c
n6.c:166:25: warning: operation on ‘(numtabp + 176u)->val’ may be undefined [-Wsequence-point]
>>> cd /usr/local/plan9/src/cmd/vac; mk all
9c vacfs.c
vacfs.c:647:6: warning: variable ‘n’ set but not used [-Wunused-but-set-variable]
>>> cd /usr/local/plan9/src/cmd/venti/srv; mk all
9c mirrorarenas.c
mirrorarenas.c:66:29: warning: variable ‘endindx’ set but not used [-Wunused-but-set-variable]
* Installing everything in /usr/local/plan9/bin...
