it seems to me that there is still something wrong:
1) the new is_qdtext_char() is incorrect.
There is a trap if char is implemented as signed char.
Suppose that c is '\xFF', it will be -1 when converted to an int.
By definition, c should be qdtext:
qdtext = <any TEXT except <">>
TEXT = <any OCTET except CTLs, but including LWS>
OCTET = <any 8-bit sequence of data>
2) the character after '\\' could be either part of a quoted-pair
(together with '\\'), or a normal qdtext, since '\\' itself can
be treated as a qdtext. This is equivalent to saying that the
character after '\\' in a quoted string could be ANY octet.
A patch based on the above two observations is attached.
Peng
f10730f616