[Bug libstdc++/11584] ios::iword() fails to zero-initialize storage on failure

["ehrhardt at mathematik dot uni-ulm dot de" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11584


ehrhardt at mathematik dot uni-ulm dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-07-29 16:56:56
               date|                            |
            Version|3.2                         |3.3


------- Additional Comments From ehrhardt at mathematik dot uni-ulm dot de  2003-07-29 16:56 -------
I think I can confirm this. 27.4.2.5 states about the iword function:

| Returns: On success iarray[ idx]. On failure, a valid long&
| initialized to 0.

Currently _M_grow_words returns a reference to _M_word_zero which is
initially set to zero but there is no guarantee that this continues
to be the case. The solution is to set _M_word_zero to 0 in _M_grow_words
before returning a reference to it.

This is ok because p2 states:

| The reference returned may become invalid after another call to the
| object's iword member with a different index, after a call to its
| copyfmt member, or when the object is destroyed.

I'll attach a proposed patch that should fix this. However, I can't
regtest 3.4 at the moment due to libiconv Problems with the testsuite.