---- Le dim., 28 févr. 2021 17:11:48 -0500 Waldek Hebisch hebisch@math.uni.wroc.pl écrit ----
That is old version. Current one is at github: https://github.com/hebisch/gpc
Yeah... I seems to get the same errors with your version as the one I had downloaded priorly.
And I get errors with compiling such old gcc with the version 10 of gcc. I could easily try version 9.
With which newer version of gcc you build the gpc+older gcc?