Uninitialized struct variable in C causes warning which is treated as an error

nitay-joffes-macbook-pro:c nitay$ pwd
/Users/nitay/code/zookeeper/src/c

nitay-joffes-macbook-pro:c nitay$ make
make all-am
/bin/sh ./libtool --tag=CC --mode=compile gcc -DHAVE_CONFIG_H -I. -I./include -I./tests -I./generated -Wall -Werror -g -O2 -MT zookeeper.lo -MD -MP -MF .deps/zookeeper.Tpo -c -o zookeeper.lo `test -f 'src/zookeeper.c' || echo './'`src/zookeeper.c
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I./include -I./tests -I./generated -Wall -Werror -g -O2 -MT zookeeper.lo -MD -MP -MF .deps/zookeeper.Tpo -c src/zookeeper.c -fno-common -DPIC -o .libs/zookeeper.o
cc1: warnings being treated as errors
src/zookeeper.c: In function 'zoo_add_auth':
src/zookeeper.c:2378: warning: 'auth.buff' may be used uninitialized in this function
src/zookeeper.c:2378: warning: 'auth.len' may be used uninitialized in this function
make[1]: *** [zookeeper.lo] Error 1
make: *** [all] Error 2

Need to set auth.buff and auth.len to zero.