bpo-12743: Delete comment from marshal.rst (pythonGH-8457)

Also, update the list of exceptions that may raised by PyMarshal_*
functions. We usually don't document exceptions raised by a
function, but in this case most of them were already documented
in C API and standard library documentation.

Doc/c-api/marshal.rst

@@ -40,20 +40,15 @@ unmarshalling.  Version 2 uses a binary format for floating point numbers.
 
 The following functions allow marshalled values to be read back in.
 
-XXX What about error detection?  It appears that reading past the end of the
-file will always result in a negative numeric value (where that's relevant),
-but it's not clear that negative values won't be handled properly when there's
-no error.  What's the right way to tell? Should only non-negative values be
-written using these routines?
-
 
 .. c:function:: long PyMarshal_ReadLongFromFile(FILE *file)
 
    Return a C :c:type:`long` from the data stream in a :c:type:`FILE\*` opened
    for reading.  Only a 32-bit value can be read in using this function,
    regardless of the native size of :c:type:`long`.
 
-   On error, raise an exception and return ``-1``.
+   On error, sets the appropriate exception (:exc:`EOFError`) and returns
+   ``-1``.
 
 
 .. c:function:: int PyMarshal_ReadShortFromFile(FILE *file)
@@ -62,16 +57,17 @@ written using these routines?
    for reading.  Only a 16-bit value can be read in using this function,
    regardless of the native size of :c:type:`short`.
 
-   On error, raise an exception and return ``-1``.
+   On error, sets the appropriate exception (:exc:`EOFError`) and returns
+   ``-1``.
 
 
 .. c:function:: PyObject* PyMarshal_ReadObjectFromFile(FILE *file)
 
    Return a Python object from the data stream in a :c:type:`FILE\*` opened for
    reading.
 
-   On error, sets the appropriate exception (:exc:`EOFError` or
-   :exc:`TypeError`) and returns *NULL*.
+   On error, sets the appropriate exception (:exc:`EOFError`, :exc:`ValueError`
+   or :exc:`TypeError`) and returns *NULL*.
 
 
 .. c:function:: PyObject* PyMarshal_ReadLastObjectFromFile(FILE *file)
@@ -84,15 +80,15 @@ written using these routines?
    file.  Only use these variant if you are certain that you won't be reading
    anything else from the file.
 
-   On error, sets the appropriate exception (:exc:`EOFError` or
-   :exc:`TypeError`) and returns *NULL*.
+   On error, sets the appropriate exception (:exc:`EOFError`, :exc:`ValueError`
+   or :exc:`TypeError`) and returns *NULL*.
 
 
 .. c:function:: PyObject* PyMarshal_ReadObjectFromString(const char *data, Py_ssize_t len)
 
    Return a Python object from the data stream in a byte buffer
    containing *len* bytes pointed to by *data*.
 
-   On error, sets the appropriate exception (:exc:`EOFError` or
-   :exc:`TypeError`) and returns *NULL*.
+   On error, sets the appropriate exception (:exc:`EOFError`, :exc:`ValueError`
+   or :exc:`TypeError`) and returns *NULL*.