Undefined behavior in dos_rw_record_fcb

[johnsonjh]

From Cppcheck v2.15.0:

src/dos.c:388:53: error: Read and write operations without a call to a positioning function (fseek, fsetpos or rewind) or
 fflush in between result in undefined behaviour. [IOWithoutPositioning]
    unsigned n = write ? fwrite(buf, 1, rsize, f) : fread(buf, 1, rsize, f);
                                                    ^

[dmsc]

I don't know if this is valid - as we only read or write to the file depending on the DOS call, so if a DOS program mixes reads and writes without a flush, is there a valid behaviour?

I will think on a way to actually flush the file when detecting mixed reads or writes.