Compiling on Linux/i586 I get these warnings:
nss_db/db-initgroups.c:60:3: warning: implicit declaration of function
'strlen' [-Wimplicit-function-declaration]
nss_db/db-initgroups.c:74:7: warning: implicit declaration of function
'strncmp' [-Wimplicit-function-declaration]
Fixed with inclusion of <string.h>