[Bug libstdc++/37958] num_get<>::do_get(bool) sets eofbit flag incorrectly when boolalpha == true

["tsyvarev at ispras dot ru" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #9 from tsyvarev at ispras dot ru  2008-11-01 12:21 -------
Patch seems doesn't resolve problem entirely.
The thing is that, besides of constraints on setting eofbit flag, the standard
claims, that comparision (in == end) should be perfomed only when it is needed
for identify a match(22.2.2.1.2, p15): 

"Successive characters in the range [in,end) (see 23.1.1) are obtained and
matched against corresponding positions in the target sequences ONLY as
necessary to identify a unique match. The input iterator in is compared
to end ONLY when necessary to obtain a character."

If also take into account constraints on setting eofbit flag:

"if, when seeking another character to match, it is found that (in == end)" and
"if the reason for the failure was that (in == end).",

one may conclude, that

eofbit flag should be set IF and ONLY IF comparision (in == end) was performed
and it returned true.


Declaration

bool __testeof = __beg == __end;

in the patched code means, that implementation always compares (in == end) at
start, even when input and target sequences are empty (""). In that case, err
will be set to failbit, which conforms to the example in the standard:

"For empty targets (""), any input sequence yields err == str.failbit"

But input sequence should not be read at all in this case, so comparision (in
== end) should not be performed!

There are also other cases, when implementation performs unnecessary
comparision (in == end).


-- 

tsyvarev at ispras dot ru changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37958