https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119705
--- Comment #9 from Patrick Palka <ppalka at gcc dot gnu.org> --- With -fsyntax-only and a checking compiler (which means frequent GCs), we allocate 5.8GB of GC memory according to -ftime-report, but maximum RSS is 5GB according to /usr/bin/time -v, which I think means the front end creates at most around 800MB of garbage. So even if we plug all leaks we're still not close to Clang's purported >50% less memory use. What is Clang's compile time/memory use with and without -fsyntax-only for this testcase?
