Tests as for fedora-gcc but with GCC trunk aka pre-13.0.0 -- the logs record the snapshot used.. 2023-01-18: gcc 13 is now nearing release. Further details as https://www.stats.ox.ac.uk/pub/bdr/Rconfig/r-devel-linux-x86_64-fedora-gcc Reports that types such as uint64_t are undeclared indicate that header (C++) or (C) have not been included explicitly -- they are presumably included by some other header on earlier versions of gcc, or by other compilers or platforms. See also https://gcc.gnu.org/gcc-13/porting_to.html . Some check results show that gcc 13 is not giving compilation warnings that gcc 12 is -- or additional warnings.