Back to my installation, I encountered this error when I "make" FS:

CC ftmod_r2_la-ftmod_r2.lo
src/ftmod/ftmod_r2/ftmod_r2.c: In function 'ftdm_r2_on_dnis_digit_received':
src/ftmod/ftmod_r2/ftmod_r2.c:1024:18: error: variable 'r2data' set but not used [-Werror=unused-but-set-variable]
ftdm_r2_data_t *r2data;

I did "boostrap.sh" and "./configure --enable-core-odbc-support --enable-core-pgsql-support". I also tried adding this configure flag "--enable-64". Whats wrong?

This is just a warning that is being treated as an error.

I pushed this fix: https://freeswitch.org/stash/projects/FS/repos/freeswitch/commits/7b9184e94fe57e0921974a70697c6d5760f717ba

You can try cherry-picking this into your 1.6 branch (git cherry-pick 7b9184e94fe57e0921974a70697c6d5760f717ba)

At some point that fix will find its way into 1.6, but not sure how often master is merged into 1.6, so I don't know when.