Hello. Commit 2e5e37249f09e54bb62e3ab87508e43ff709a4fb should improve the situation. It reverts the part affecting s-os_lib.adb. A GCC build produces the same checksum for it than 9.3.0-8 in libgnat-9, hopefully making gnat usable again by existing packaged libraries (I don't know how to test this on a porterbox). The remaining part, slightly adapted, passes the regression tests for this specific bug.
If all goes well, please lower the severity of this bug, but keep it open as a reminder. * Unless an objection arises, the gcc-10 branch should eventually cherry-pick c1d276b0e2cb60140389aa4c23ac3addb7a77af3. * Ludovic has noticed that the initial error message CONSTRAINT_ERROR : uintp.adb:1959 overflow check failed probably reveals a bug that should be investigated by itself. No time computation is supposed to trigger a range overflow in an unrelated package.