Can sizeof(int) ever be 1 on a hosted implementation?

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It is possible for an implementation to meet the interface requirements for fgetc and fputc even if sizeof(int) == 1.

The interface for fgetc says that it returns the character read as an unsigned char converted to an int. Nowhere does it say that this value cannot be EOF even though the expectation is clearly that valid reads “usually” return positive values. Of course, fgetc returns EOF on a read failure or end of stream but in these cases the file’s error indicator or end-of-file indicator (respectively) is also set.

Similarly, nowhere does it say that you can’t pass EOF to fputc so long as that happens to coincide with the value of an unsigned char converted to an int.

Obviously the programmer has to be very careful on such platforms. This is might not do a full copy:

void Copy(FILE *out, FILE *in)
{
    int c;
    while((c = fgetc(in)) != EOF)
        fputc(c, out);
}

Instead, you would have to do something like (not tested!):

void Copy(FILE *out, FILE *in)
{
    int c;
    while((c = fgetc(in)) != EOF || (!feof(in) && !ferror(in)))
        fputc(c, out);
}

Of course, platforms where you will have real problems are those where sizeof(int) == 1 and the conversion from unsigned char to int is not an injection. I believe that this would necessarily the case on platforms using sign and magnitude or ones complement for representation of signed integers.

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