undefined reference to `yywrap' compiling PAM

If you get this error while compiling pam modules ,

be sure you have flex package as installed..

I was working on debian.

/home/eren/PAM/Linux-PAM-1.1.1/conf/pam_conv1/pam_conv_l.c:871: undefined reference to `yywrap'
collect2: error: ld returned 1 exit status
make[4]: *** [pam_conv1] Error 1
make[4]: Leaving directory `/home/eren/PAM/Linux-PAM-1.1.1/conf/pam_conv1'
make[3]: *** [all] Error 2
make[3]: Leaving directory `/home/eren/PAM/Linux-PAM-1.1.1/conf/pam_conv1'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/home/eren/PAM/Linux-PAM-1.1.1/conf'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/eren/PAM/Linux-PAM-1.1.1'
make: *** [all] Error 2

i fix this problem by installing flex package in debian repository.

apt-get install flex

i hope , it also works for you.