1. What version of distcc are you using (e.g. "2.7.1")?
svn revision 618

2. What platform are you running on (e.g. "Red Hat 8.0", "HP-UX 11.11")?
Gentoo, x86-64, gcc-4.1.2, glibc-2.6.1, python-2.5.2

3. What were you trying to do (e.g. "install distcc", "build Mozilla")?
$ svn co distcc; ./autogen.sh; ./configure; make

4. What went wrong?
(snip)
x86_64-pc-linux-gnu-gcc -pthread -fno-strict-aliasing -g -O2 -MD -W -Wall
-Wimplicit -Wuninitialized -Wshadow -Wpointer-arith -Wcast-align
-Wwrite-strings -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes
-Wnested-externs -Wmissing-declarations -pthread -DHAVE_CONFIG_H
-D_GNU_SOURCE -DSYSCONFDIR=/usr/local/etc
-DPKGDATADIR=/usr/local/share/distcc -Isrc -I./src -I./lzo -fPIC
-D_GNU_SOURCE=1 -Isrc -I./src -I./lzo -I/usr/include/python2.5 -c
-D_GNU_SOURCE=1 -Isrc -I./src -I./lzo -I/usr/include/python2.5 -c
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c
-o
./_include_server/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.o
-W -Wall -Wimplicit -Wuninitialized -Wshadow -Wpointer-arith -Wcast-align
-Waggregate-return -Wstrict-prototypes -Wnested-externs -Werror
-Wp,-U_FORTIFY_SOURCE
cc1: warnings being treated as errors
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c:26:
warning: initialization discards qualifiers from pointer target type
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c:31:
warning: initialization discards qualifiers from pointer target type
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c:384:
warning: no previous prototype for 'initdistcc_pump_c_extensions'
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c:
In function 'initdistcc_pump_c_extensions':
/tmp/distcc-read-only/include_server/c_extensions/distcc_pump_c_extensions_module.c:388:
warning: passing argument 1 of 'PyErr_NewException' discards qualifiers
from pointer target type
error: command 'x86_64-pc-linux-gnu-gcc' failed with exit status 1
make: *** [include-server] Error 1

following patch solved them.
http://sources.gentoo.org/viewcvs.py/*checkout*/gentoo-x86/sys-devel/distcc/files/distcc-3.0-gentoo.patch?rev=1.1