Warnings from clang 7.0 when compiling dovecot-openssl-common.c from dovecot 2.3.5 with openssl 1.1.1a.

This is dovecot's configuration:

config_options="--prefix=$prefix \
    --sysconfdir=$prefix/etc \
   --datarootdir=$prefix/share \
   --mandir=$man \
   --docdir=$doc \
   --with-docs \
    --with-ssl=openssl --with-ssldir=$prefix/etc \
   --with-sodium \
   --with-libiconv-prefix=/opt/libiconv \
   \
   --with-bzlib=no \
   --with-gssapi=no \
   --with-ldap=no \
   --with-lucene=no \
   --with-lz4=no \
   --with-lzma=no \
   --with-pam=no \
   --with-solr=no \
   --with-sql=no \
   --with-vpopmail=no \
   --with-zlib=no \
   \
   --enable-dependency-tracking";

Note on passing: --with-ssldir=$prefix/etc is ignored by the configurator, as it forces $prefix/etc/dovecot.