Jonathan Wakely <[email protected]> writes:
> This adds move and swap functions to the iostream classes.
>
> Although this is a pretty large patch, it's a pure addition that only
> affects C++11 mode, and should have no effect on existing code because
> it won't be moving or swapping streams.
>
> I wanted to use C++14's std::exchange so I added std::__exchange to
> <bits/move.h> and made std::exchange forward to that.
>
> I needed to add a new constructor to basic_ostream that doesn't call
> init(0), for basic_iostream's move constructor to use. (I wonder why
> our non-standard default constructors for basic_istream and
> basic_ostream call init(nullptr), rather than doing nothing. Derived
> classes that want init(nullptr) to be called can do that by passing
> nullptr to the standard basic_istream and basic_ostream constructors
> taking a pointer, which would allow the default constructors to be
> re-purposed to intentionally leave the object uninitialized).
>
> To ensure that the explicit instantiations in the library include the
> new functions I had to move several files from src/c++98 to src/c++11,
> which makes the patch huge, so the new tests are in a separate,
> gzipped file to keep this post below the mailing list size limits.
>
> Tested x86_64-linux, committed to trunk.
This patch broke Solaris bootstrap with Sun ld: when linking
libstdc++.so, ld complains
ld: fatal: libstdc++-symbols.ver-sun: 4520: symbol 'std::basic_ios<char,
std::char_traits<char> >::move(std::basic_ios<char, std::char_traits<char>
>&&)': symbol version conflict
and many more. In that case, I find that this symbols is matched by
both the GLIBCXX_3.4 and GLIBCXX_3.4.21 patterns:
GLIBCXX_3.4
##std::basic_i[g-r]* (cxx)
_ZNSt9basic_iosIcSt11char_traitsIcEE4moveEOS2_;
GLIBCXX_3.4.21
##_ZNSt9basic_iosI[cw]St11char_traitsI[cw]EE4moveE[OR]S2_ (glob)
_ZNSt9basic_iosIcSt11char_traitsIcEE4moveEOS2_;
Rainer
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Rainer Orth, Center for Biotechnology, Bielefeld University
