Notice how the vendor field is mostly irrelevant and is usually 'pc' for 32-bit x86 systems or 'unknown' or 'none' for other systems. The simple three-field target triplet we have seen so far is unambiguous and easy to parse. However, since the vendor field is mostly unused, the GNU build system allows you to leave out the vendor field; the build system will automatically insert a default vendor part when it disambiguates your target triplet. For instance, this allows you to type: x86_64-freebsd The build system will then automatically deduce that the vendor is the default (unknown) if it wishes to know the unambiguous target triplet. Note that parsing target triplets are a bit more tricky, as sometimes the operating system field can be two fields: x86_64-unknown-linux-gnu This gets a bit worse since the vendor field can be left out: x86_64-linux-gnu This is most definitely ambiguous. Most autoconf-based packages ship with a huge shell script called config.sub whose function is to disambiguate target triplet using a long list of known CPUs and known operating systems.