[Bug libstdc++/79254] [5/6/7 Regression] basic_string::operator= isn't exception safe

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79254

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Wed Feb  1 11:41:48 2017
New Revision: 245085

URL: https://gcc.gnu.org/viewcvs?rev=245085&root=gcc&view=rev
Log:
PR libstdc++/79254 simplify exception-safety in copy assignment

        PR libstdc++/79254
        * config/abi/pre/gnu.ver: Remove recently added symbols.
        * include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
        (basic_string::_M_copy_assign): Remove.
        (basic_string::operator=(const basic_string&)): Don't dispatch to
        _M_copy_assign. If source object is small just deallocate, otherwise
        perform new allocation before making any changes.
        * include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
        (basic_string::_M_copy_assign(const basic_string&, true_type)):
        Remove.
        * testsuite/21_strings/basic_string/allocator/char/copy_assign.cc:
        Test cases where the allocators are equal or the string is small.
        * testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
        Likewise.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/config/abi/pre/gnu.ver
    trunk/libstdc++-v3/include/bits/basic_string.h
    trunk/libstdc++-v3/include/bits/basic_string.tcc
   
trunk/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc
   
trunk/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc