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.