Years ago I ported some software from IRIX to some Linux-based OS. There were a few differences in the result. I eventually tracked it down to how on IRIX char

Years ago I ported some software from IRIX to some Linux-based OS. There were a few differences in the result. I eventually tracked it down to how on IRIX char is unsigned while the Linux-based OS used signed char. The program used a 'char' to store the value of the formal atomic charge of an atom, which is typically 0, but for the sorts of chemistry I deal with can be +1, +2, -1, or -2, so it makes sense to allocate only 8 bits to store the 'char'ge. :) On IRIX, where they had deployed the code for years, the charges were actually being interpreted as 0, +1, +2, 255, and 254. Going back to the code example you gave, isn't there also an issue if read failure occurs on the first byte? Then `out` is 0, returning -0, which is 0, giving no way for the caller to distinguish between EOF and read failure.