gentoo-overlay/dev-libs/log4cxx/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<herd>cpp</herd>
<use>
  <flag name='smtp' restrict='&lt;dev-libs/log4cxx-0.10'>Offer SMTP support via
    <pkg>net-libs/libsmtp</pkg></flag>
  <flag name='smtp' restrict='&gt;=dev-libs/log4cxx-0.10'>Offer SMTP support via
    <pkg>net-libs/libesmtp</pkg></flag>
</use>
</pkgmetadata>