https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107173
--- Comment #3 from Esa Pulkkinen <esa.pulkkinen at iki dot fi> --- I realize also -E option is necessary for the problem. I tried various flags to enable/disable modules support (e.g. -fmodules-ts), but those seem not to impact the problem, though they impact what happens if I do more than just the preprocessing step.