Demi Marie Obenour writes: > On 11/13/25 13:01, Alyssa Ross wrote: >> Demi Marie Obenour writes: >> >>> On 11/13/25 08:21, Alyssa Ross wrote: >>>> Demi Marie Obenour writes: >>>> >>>>> + if (entry->d_name[0] == '.') >>>>> + if (len == 1 || (len == 2 && entry->d_name[1] == '.')) >>>>> + continue; >>>>> + unsigned char c = (unsigned char)entry->d_name[0]; >>>>> + if (!((c >= 'A' && c <= 'Z') || >>>>> + (c >= 'a' && c <= 'z'))) >>>>> + errx(EXIT_FAILURE, "Filename must begin with an ASCII letter"); >>>> >>>> Would the comparison not be valid without the cast? >>> >>> It would be in this case, but the subsequent cast to int in the error >>> path assumes that the cast was done. Signed characters are much >>> trickier and casting to unsigned makes the code easier to reason about. >> >> Is it safe to assume 'A' etc. are representable and comparable as >> unsigned values? (I'm sure it is in practice, but I'd like it if I >> could be confident this is being done strictly correctly.) > > I don't know if the C standard requires it, but we assume it. Is it a safe assumption, at least on all Linux architectures?