ltrace 0.8 (prerelease) has a -w option for stack unwinding, but it is not enabled in Fedora's build. I think it just need BuildRequires libunwind-devel *or* elfutils-devel. I expect the latter is preferable, but may require a newer snapshot too.
ltrace-0.7.91-13.fc21 has been submitted as an update for Fedora 21. https://admin.fedoraproject.org/updates/FEDORA-2015-0339/ltrace-0.7.91-13.fc21
ltrace-0.7.91-13.fc21 works
Package ltrace-0.7.91-13.fc21: * should fix your issue, * was pushed to the Fedora 21 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing ltrace-0.7.91-13.fc21' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2015-0339/ltrace-0.7.91-13.fc21 then log in and leave karma (feedback).
ltrace-0.7.91-13.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.