Read()'s return value is the only bound on how many bytes are valid in
the caller's buffer; ignoring it is what caused the identfile OOB read.
All existing callers already use the result, so flag the rest at compile
time.
Read() returned up to 1024 bytes into a stack buffer that was then
assigned to a CString via the const char* overload, so strlen() walked
past the end of buf when the file filled all 1024 bytes without a NUL.
ReadFile() bounds the append by the byte count Read() returns and reads
the whole file, so the original contents also round-trip faithfully.
rootvector2